Fine Engine Tuning With A Vacuum Gauge

Here's everything you need to know about using a vacuum gauge as a tuning device. A few great ways to dial things in, and one that definitely sucks.

[@classiccars1152]

allways manifold vacuum on dis advance .....ported is a emmision thing ..... As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative. TIMING AND VACUUM ADVANCE 101 The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency. The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation. At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph). When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean. The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic. Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it. If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more. What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone. Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam. For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it - they don’t understand it, they're on commission, and they want to sell "race car" parts. __________________

[@dustinginter7514]

I read this a few years ago, made sense then, and still does today. Thanks for your efforts.

[@jonfranklin9361]

Thanks! Make perfect sense.

[@Dizzle13]

Thanks!

[@zombeesama1169]

as a beginner and a DIY, how can say where is my manifold vacuum on my carb?

[@mikesawyer4707]

If I close my eyes I can hear my dad talking cars, and car maintenance. I wish I would have listened a lot closer to my dad. Uncle Tony you rock.

[@willbaldwin8165]

I feel the same way about my father. He’s been gone for 10 years., and he knew everything about carbureted engines , he could time a engine just by listening to it while he turned the distributor and get it right on the money

[@charlesvaughan6063]

Your 30 second explanation of how to tune the springs in an Edelbrock helped me understand it better than I ever did reading the manual that came with it and watching a bunch of other videos. Thanks, Uncle Tony!

[@briansage7552]

👍

[@briansignorelli7090]

Reading that Edelbrock manual caused man to want to drink

[@jfeliciano2687]

You are a national treasure... Every old guy I meet tries their best to hold on to this information and then wonders why nobody want to use a carburetor and swaps everything to FI.

[@AmericanThunder]

I'm a former Holley carb builder and tuner, and I moderate an engine group on facebook, I try to teach the younger generation about carbs, but I usually find that their minds are deadset against it because it's "old tech".

[@jdruin1]

@@AmericanThunder When I was working on cars back in the nineties, I got all the electronic issues cause I was really good/fast at them (brakes too but that’s a different story). It caused me to not learn carbs like I should. No longer a mechanic by trade, but trying to learn the old stuff. While I can tune a fi system for performance, I can’t a carb yet. That just chaps me. Time to go old school

[@MrYAMAHA32177]

Refreshing to see old some school tuning again, no laptops required, thanks to uncle Tony.

[@hectorrivera8685]

Nice video with some good information. Here are some important clarifications: 1) vacuum should be checked with the air cleaner ON. Checking it without the air cleaner results in inaccurate readings, and your adjustments will be wrong. 2) Before adjusting the idle mixture screws, the engine timing at the distributor should be checked, and the idle speed should also be adjusted. Both of these come _before_ tuning the idle mixture screws with a vacuum gauge. 3) The engine should be HOT when checking vacuum. Uncle Tony started up the engine and immediately checked vacuum. I assume the engine had recently been running, but the point was never addressed. 4) The idle mixture screws should be turned in sequence, 1/4 turn on one, then 1/4 turn on the other. That way they're equal. If you adjust one screw for absolute maximum vacuum before adjusting the other screw, it's guaranteed that the screws won't be equally adjusted at the end of the process. And both screws should be equally adjusted.

[@Corsairforu]

For your #3 go back and listen about 8:25 mark

[@mattbauckman9907]

I’m a strong proponent of full manifold on vac advance. I’ve curved the distributor on my 396 to run this way and it’s a raped ape. Excellent fuel mileage too. Bone stock original 325 h p cam, 89,000 original miles. When set up properly you can achieve a strong running engine either way. Whatever works for your application, as I’ve seen it both ways over the years. Thanks for sharing your knowledge Tony. The vacuum gauge is one of those forgotten tools, but not for us old iron guys. Now break out your dwell meter and REALLY confuse the younger generation 😂

[@asus6983]

Manifold is genuinely pretty useless for a driver. You just leave efficiency on the table, although for something that sees zero vacuum more often than not, then the choice becomes irrelevant.

[@mattbauckman9907]

asus6983 Read the link I posted. It will prove that wrong.

[@540EdgeFlyer]

Anyone who actually takes the time to understand the air/fuel conditons of an engine at differing throttle positions, and loads, and the corrosponding timing requirements will understand why Manifold vac is the most useful method for a street driven engine. Ported vacuum can be made to work acceptably, but more initial timing is required, and economy, and street manners are sacraficed.

[@hotrodcasanova3574]

Manifold vacuum works the best. But if your using an hei distributor you need to limit the vacuum advances range to 10-12° of total movement. Similar to the vacuum advance range of a presmog points distributor which is usually 0-12° vacuum advance at full vacuum. Where a stock hei vacuum advance range can turn it 0-30degrees advance on some distributors.

[@fixedgear37]

Modern turbo builds and younger guys use vacuum readings more than you realize. “Old iron” doesn’t matter, vac matters on all builds.

[@moparedtn]

Once again, the Man dispenses the gospel to the masses as simply as possible, therefore making it totally understandable and accessible even to the novices. This channel may be a lot of things, but the one that's always impressed me about Tony is how willing he is to share knowledge and help anyone who wants to know. BTW, this old goat just learned a new trick with that "checking the spring tension on the needle valve" bit on the Edelbrock. I've always just sort of stumbled my way along, using the infamous "chart" we all get with the AVS carbs as guidance until I hit on something that works. Tony's way saves a TON of time! Thanks as always, keep 'em calm over there in the flatlands neighbor, -Ed on the Ridge

[@zxej6879]

The lost art that many mechanics never had.

[@brucejones2354]

Boy, you got that right! ! !

[@PeterSmith-or3pq]

My Dad .had a great ability to do that ..

[@spambeanie2]

this guy's a moron he don't know what he's talking about He's trying to act like he does because he's got a little bit of mechanical skill but he doesn't know what he's talking about I could tell you every emission part on anything from the '70s through the '97 OBD1 and I can do OBD2

[@spambeanie2]

And I'm watching him use a screwdriver on an Edelbrock performer carburetor use your fingers you can do it with one hand and hold the vacuum gauge with the other

[@spambeanie2]

I don't even use a vacuum gauge for that I'll set the static initial timing with a vacuum gauge you know when I see what the motor where it wants to run at an idle where the vacuum needs or the advance needs to be and then I'll set the advanced curve according to the camshaft and then I'll tune the carburetor by ear I don't need a vacuum gauge I can feel it and hear it you couldn't do any better with the vacuum gauge

[@StuartKReilly]

Mister Tony. I'm only 29 but I've played around with and drove classics since I was old enough to drive and before then some. If I would have had even a quarter of the knowledge you have on these carbureted engines when I was younger I probably woulda kept a lot of my old projects. Now that I'm getting back into it with a new project in the age of KZbin and Google I've made it a mission to arm myself with actual facts and info about keeping these cars running and your videos have been the biggest help out of anything else I've watched. So thank you for sharing everything you know about old school cars with young bucks like me.

[@KP-qh8je]

Another good channel is Muscle Car Solutions. Uncle Tony knows mopars and I'm a mopar guy

[@bbb462cid]

Every old-skool car guy has a vacuum gauge and dwell/tach in the milk crate that's in the trunk. I don't actually know where the milk crates came from, I just know I always had a few, lying around. Maybe they grow in old car trunks.

[@nickmcwilliams685]

Have you noticed the coffee cans are popping up plastic now?

[@bbb462cid]

@@nickmcwilliams685 yeah, mixed feelings about it. I'm sure I have a Chock full O'Nuts can rusting here someplace...

[@deborahchesser7375]

Mr. Blutarsky they come from under old dirt bikes

[@bbb462cid]

@@deborahchesser7375 that must be it!

[@terrycopas4219]

Your right they do grow back there! I have one in my 67 Camaro with the timing light, dwell meter and vacuum guage along with cleaning supplies, all necessary tools to do about anything that might possible to wrong on a road trip! Bikers know what I'm referring to also!!! Need to watch out though because that coil of 16 or 18 guage wire you have in there for emergencies attracks mice which in return attracks snakes, like your common rat snake and black snakes!!! I kid you not, this actually occurs with the old 60s cars, they attract critters that love eating the insulation on the wiring from those years of cars! It happened to me! Had a mouse run up from the rear of the car after I started it and just ran out on my arm that I had laying on the door, you know like you leave your arm after adjusting your mirror, anyway he stopped at about my elbow and just started at me, must have been for 2-3 minutes we both just looked at each other, thought it was kinda cool at first then I thought about all the shorts he could cause, so I shook the heck out of my arm and he fell off to the garage floor and I took care of him, you know!!! Then later on that day was driving down the Interstate profiling in my gorgeous Quasar Blue 67 Camaro when I felt something kinda cold and moving up my bare leg due to wearing short pants that day and when I looked down saw a grayish looking snake with diamond makings on his back!! Needless to say this scared the crap out of me 😂 and I immediately switched lanes as physically possible over to the side of the road and immediately 😬 without any concern for safety, I mean I just had what I thought was a medium sized rattle snake slither up my naked leg for Christ sake, anyway I began trying to catch the little bastard with the work gloves I had found in the milk crate in the trunk, the 🐍 snake slithered into the heater vent on the driver's side of the console, that really was a bummer, was at a loss for a minute then decided to start the car back up and turn the heater on full blast, it worked the snake come hauling ass out of the hot vent, I saw he had no rattles on his tail and his head was not shaped like a poisonous 🐍 snake, whew gave me some relief, my BP returned to normal as did pulse and respiration, then the 🐍 slithered under the driver's seat, grabbed the largest screwdriver I could find from the milk crate and began chasing the huge fucker, he had miraculasly grown twice his original size, so here we go me head on the floor looking for the 🐍 snake, if he would have crawled toward me, that would have been it, ❤️ heart attack for sure! Luckily he didn't, he slithered under the back seat!! Oh boy, here I go tearing out the entire back seat of my precious 67 Quasar Blue Camaro on the side of the road on the Interstate! Got it all out 👍 faster than ever before because that 🐍 snake had slithered his way into the trunk and ended up in the milk crate!! I couldn't see him at all, he had hidden himself up under some shop rags! Now, by this time 2 other cars had stopped to see if I needed assistance, this happens when you ride a Harley and stop on the side of the Interstate or in a gorgeous classic car, folks just stop to see if there is anything at all they can help you with, just like in the old days!!! Anyway with my audience watching I was still nervously searching for the monster of a 🐍 snake, amazingly it just kept getting bigger and bigger all the time I was chasing it! With everyone looking on I picked up the milk crate and began to dump it in the trunk when the monster of a 🐍 snake came slithering out onto to trunk floor and curled himself around my left original tail light and at that time a guy about 18 I presume reached in, grabbed the monster 🐍 snake by the tail and uncurled him from around my 67 Camaro original tail light lifted him out of the trunk, showed him to all the concerned citizen s that had stopped to assist and explained it was a Rat 🐍 snake, he knew this because he was a Marine and had seen many snakes at Camp Lejeune and Paris Island so after holding it without any worries of being bit, he walked over to the edge of the forest on the side of the Interstate and ever so gently turned the little 🐍 snake loose into the woods! Now I know everyone is thinking how they would have felt with this situation so much different than I did, but until you have any kind of 🐍 snake crawl up your naked leg while your driving your gorgeous Quasar Blue 67 Camaro SS down the Interstate at 70 MPH you really can't say for sure exactly what your reactions would be!! I personally was so thankful for my milk crate that not only had everything I might have needed should my gorgeous Quasar Blue 67 Camaro SS might have broken down, not ever, but pays to always be prepared, just so happened I had everything required to Chase and capture extremely large snakes should the situation arrise!!! Just shows to go you how important that milk crate can be! So if you ever happen to see one at a yard sale, back of a old closed down grocery store, Craig's list or EBay, better but it, it could end up saving your life!! Really when you think about it, thousand wonders I did not wreak when I first looked down and saw that monster of a 🐍 snake crawling up my leg while driving my gorgeous Quasar Blue 67 Camaro SS down the Interstate! So just a little bit of advice 😉 place moth balls all around your garage to run the snakes off and I heard placing dryer sheets under your car seats and you can always store the box of sheets left over in your milk crate in your trunk! They are priceless!!! Hope you enjoyed my story, every bit of it was true!! Be safe out there and speed safely!!!GOD BLESS ALL AMERICANS!!!!

[@fenastray]

Your level of knowledge is impressive.

[@spankyham9607]

These are the kind of tech videos I really like and get a lot of useful knowledge out of. I like knowing the "why and when" to something and not just how.

[@NebukedNezzer]

remember when JC Witney sold variable ignition timing kit so you could adjust your timing as you were driving. My first car was a 48 chevy. I tried the experiment of hooking the vacuum advance to the manifold vacuum. No, that did not work well at all. On my 48 chevy and the other old standard trans cars I had. one good way to adjust timing was this. with a hot engine and the gas you use(usually the cheapest regular). put the car in high gear at less than 20mph. step on the gas and as you accelerate it should ping a bit till you get to 30mph and then not ping there or above that. adjust the timing till you get that. now when you drive normally you get all the advance you can use because you do not normally lug the engine below 30 in high gear. you can cruse in high gear at 30 ok just not give it a lot of throttle. this would get the best gas mileage. Love your videos as you teach how this stuff is supposed to be done. if we just listen to the idle as we adjusted the mixture screw it will idle at max rpm if the idle mixture is rite. lots of stuff was done with no gages at all. do you need to have the vacuum advance working. Yes for mileage and no for power. since the vacuum advance is ported. if its not connected at all the idle is the same. also at full throttle there is very little vacuum that matters not much either. only daily drivers need the vacuum advance to work. when the vacuum advance is broken(or stuck) I would know because my mileage would drop off enough to know something was wrong.

[@chickenray182]

I think that was the MSD Ping Control.

[@jamesbetts3371]

we mounted on the dash where the radio had done been, a mallory mechanical advance box in my friends 69 roadrunner. That along with a T- valve that went from a reservoir of ATF to manifold vacuum. Hooked up a old choke push pull cable and let the show begin. A pull of the cable when driving, advance the timing and a smoke screen that James Bond would be envious of. Speaking of JC whitney we installed the exhaust cut outs they used to sell along with the lever that moved the pipe to one side on that same car. We were tired of dropping the pipes before racing at sears point every week , a few times before the cut outs we just drove home with open headers . The kit sucked and never sealed back up correctly but it was fun to open the exhaust while sitting at a light from inside the car, usually some kid talking about he was going to smoke us. The look on their faces was always the same as the exhaust sound changed and the cocky smirk went to, bewilderment and confusion, last the realization that something bad was about to happen. Those were good times!!!

[@GlamStacheessnostalgialounge]

Oh wow, I actually discovered this on my own when I just started working on my car in the mid 2000s. It just made a lot of sense to me.

[@NoName-tz5ji]

GO AWAY,your reminding me how old I am!

[@Mach141]

I had the MSD variable timing control in my 1993 mustang. Not sure it did much, would turn it up a few degrees at the track, back down for cruising

[@Czechmate_e30]

I love this channel. So many cool nuggets of information and tips. I'm a big 80s-90s euro guy, but I did own a 74 "Gold" 318 Duster for about a year. Was too young, an inexperienced to properly rebuild it so I sold it. Eight years later after watching much of this channel, I'm getting excited to give it a try once again.

[@doglvr1]

My dad was trained as a mechanic. He did all of his maintenance and most engine repairs. He always tuned an engine with just a vacuum gauge, no timing light. He taught me a lot but I always had to use a timing light because I couldn’t get it right with a vacuum gauge. That cars I tuned were a 70 AMC Gremlin 232, 70 AMC Ambassador 360 and a 78 Honda Civic CVCC. After that, things got to complicated for me with all the electronics involved. This video brought back fond memories of all my dad taught me.

[@robwelch9182]

Cracked me up at 'close enough for government work'

[@briansd2772]

Funny stuff indeed! It's an old school quip going back to the 1940's.

[@monadking2761]

Did you ever here the definition of close enough for government work it is? You measure with a micrometer, mark it with a piece of chalk then cut it with a hatchet.

[@johnbecay6887]

@@briansd2772 maybe even before to the 30s when a lot of people were working in government programs like WPA.

[@briansd2772]

@@johnbecay6887 Yep. It had a positive meaning originally.

[@UncleTonysGarage]

Ok, let me explain something about the ported vs manifold vacuum as it applies to distributor advance. If you have it hooked to manifold vacuum, it RETARDS the timing as soon as you touch the gas. The exact OPPOSITE of what you want to happen when the engine meets the initial load. Hooked to ported, it is inactive at idle as well as initial acceleration. Ported, it comes on when it is needed. Manifold, it turns off when the engine wants advance the most. Vacuum advance is intended for LIGHT throttle cruising, NOT acceleration. Make sense? I do not care which manufacturers used manifold vacuum, when they used it, or why. For best performance and to be used as originally intended, it should always be hooked to ported.

[@xmo552]

Tuning: manifold vacuum. Distributor: ported vacuum. Always. Got it. I have a question about when you actually had it running and tuning live. You were at 2 turns before it started. As soon as you started the engine you were at 16.5 for vacuum. At times it was higher. You finished it off at 16.5 again. Why? Why didn't you try to keep it at the higher vacuum signal? Please and thanks Unc'.

[@frankd8204]

Tony, but isn't vacuum advance made for idle and cruise? As you say, once off idle, you want more ignition timing, but isn't that what centrifical advance is for...built into the distributor and sensitive to rpm? Kind of like three circuits for fuel delivery in a carburetor, a distributor needs initial advance (set at the crank), idle (vacuum advance routed to manifold), and wide-open throttle acceleration (centrifical), set by weights and springs in the distributor?

[@dand232]

I agree that vacuum advance is for cruising & not acceleration, but I ALWAYS use manifold vacuum to the distributor, I have been tuning big blocks for nearly 40 years & found they always run better this way. Hook up a vacuum gauge to manifold & another to ported vacuum on the carb, route the hoses into the car & take it for a drive. At idle you have vacuum at manifold, none at port, at full throttle you have no vacuum from either, at cruising speed you have full manifold vacuum & ported vacuum varies on speed, but is less than manifold. The main advantages to using manifold vacuum is fuel economy. Set your timing & idle with vacuum disconnected as always, lets say your idle speed is 650rpms, then you plug vacuum hose back to vac advance & your idle speed jumps to lets say 8 or 900 rpms, too high, so you set idle back down to 650 with vac advance. This setting will use less fuel at idle & generally gives a smoother idle. The bigger savings is that when driving everytime your are coasting you are at this lower throttle setting & when you are cruising you are getting FULL vacuum advance too, so you maximize torque & mpg the same time, I have found this to give the average big block a 10% increase in economy, certain makes even more, especially Olds & Buicks.

[@trailerparkcryptoking5213]

You are absolutely incorrect about vacuum advance. It connects to manifold vacuum! At idle you have max vacuum which requires earlier firing of the lean mixture and causes the engine to run smoother. As the engine revs up from idle, the vacuum drops as does the vacuum advance, but the mechanical advance takes over! Now if you think I’m incorrect, which you do, get the book “Performance Ignitions and Tuning” written by Dr Christopher Jacobs. He has a PhD in electrical engineering and was the founder/owner of Jacobs Electronics which produced performance ignitions for years and MSD bought him out for millions of dollars when he took a lot of their market share. He used to consult to NASCAR and NHRA professional race teams when they had ignition problems. Dr Jacobs breaks it down in the book and no disrespect, but if you can’t top his credentials, which you can’t, then quit feeding people bad information that trust you.

[@michaelcostner5287]

@@trailerparkcryptoking5213 he also said the 440 has a small cam which makes less vacuum . also wrong .

[@ericshenette5359]

Watching this guy reminds me of working with my dad boy I miss him 😇I’m so thankful for people like him and the knowledge he puts forward thanks man ! Great work !

[@ceesteven]

I remember it well. Always had my vacuum gauge attached. An “old timer” got me started on it somewhere back then. Great tool. Only one or two other gear heads I knew used the HG. So much to speak on regarding. Glad to see your vid. You brought back some good memories. Those were the days when we learned how it all worked in order to know why it didn’t. Osac valves came in handy then. I’ll catch up to you again. Thanks for sharing.

[@bladeslicemaster5390]

Great info, I like how you actually started the engine and showed how to set the idle screws instead of just talking about it... Thanks!

[@johnstipetich9821]

THANK YOU! for covering this and answering questions I had from the last video. Plus I look forward to seeing Bottle Rocket and the slant 6 Dart run. I'm curious to see what kind of numbers they run. You and Uncle Cathy keep up the great work! 😁

[@keithcornell3173]

i learn so much from you .since im old school{62 years old) and can only work on old cars and own just pre 80s cars your the man.watching you explain and back up what your saying with demos brings me back to my days of auto shop in the 70s keep up the great work your doing.OLD SCHOOL RULES

[@thomasgarven129]

Reminds me of my Chevrolet Corvair I once had with dual carbs. Had two vacuum gages; one for each bank of cylinders. Super easy to do a tuneup when you can see exactly when and where each carb sits. Good video.

[@tacocin]

Totally agree Uncle Tony! That timing adjustment for maximum RPM never worked for me. Spark knock or pre-ignition (pinging) under load was an issue when done that way. I always set timing by taking it up a degree at a time and road test. When I heard spark knock I'd back it off one degree and be done. Of course I also knew that octane rating made a huge difference. I always tuned with fuel that was normally being used. Then for the hot rodders we could introduce things like water injection or methane to cool the combustion chamber and allow even more timing advance. Ahhhh -- the good old days!

[@walterdowns9978]

Ah yes water injection can you buy them anymore I had a holly water injection system that I bought years ago my wife threw it out in the garbage I never did get to use it. My uncle was a great mechanic God Rest his soul and he told me about the water injection he said it increases the horsepower and it cleans the engine so you end up with the cleanest engine that you can ever have with no carbon in it

[@gregsr1]

to adjust timing with a vacuum gauge, find highest vacuum then back off 2 inches. this is the best timing

[@timg2776]

@@walterdowns9978 check out snow performance. Mostly diesel applications but they sell a simple kit

[@howitstartsmm]

Back in the 70's I used basically a water fogger cause I couldn't afford a nitrous system. I would open the valve around 40 mph. It would lean the mixture out but nothing a little propane couldn't handle. Can't believe I never detonated an engine. Fun times!

[@howitstartsmm]

​@walterdowns9978 ok, before I say anything, I was a teenager in the 70's. Sporting a snorkel hood scoop, air shocks, traction bars, and a Predator carb, so not too bright. I drilled a short rise baseplate and put two mister/fogger nozzles and two threaded holes for propane. I had a small gas tank with an inline spark arrestor for the propane and a pressurized tank with water and opened both around 40mph. The water introduced an extra oxygen molecule (leaned it out) and took up space like nitrous to raise compression ratio (water doesn't compress) and the propane to help correct the lean issue. I've thought about doing it to my 77 El Camino, but maybe next weekend. Hope this helps or at least makes you go, what is wrong with that guy?

[@dennyfatiha]

Lol! I have a vacuum gauge from the late 80’s . Vacuum gauge great for tuning and diagnostics . I use to have to do it at the rest areas . When driving thru the mountains.

[@nosnerd1967]

Buddy I’m so impressed that you’re showing this to the masses ....many people do not know how to do this !!!! many mechanics- still to this day do not know how to read a simple vacuum gauge !

[@markshelton735]

Thanks for this video. I have a 73 F250. After watching this video and tuning my carb it has never run better. I've watched other guys videos and they were okay. This one got to the point real quick and got the point across. Thanks!

[@muziklvr7776]

All of my vehicles from the 1950's through the 1980's used manifold vacuum for vacuum advance, requiring the vac line be disconnected from the advance can and plugged off (I always used a golf tee) to check and set ignition timing. Some heavily emsioned vehicles (mainly 1974-ish through the early 80's California emission) used ported vacuum to reduce HC at idle or used a valve that delayed vacuum to the distributor like an OSAC valve (Chrysler version), sometimes using both methods (most of these engines were complete dogs and obtained horrible fuel mileage). Modified engines with hotter cams sometimes required ported vacuum, depending on the setup. This was usually a crutch though. The best method was to us an adjustable vacuum advance can and tune it, after the distributor weight springs were properly selected. Full out race engines back in the day didn't use vacuum advance and generally locked out the centrifugal weights in the distributor. In the 1980's, dual diaphragm vacuum advance cans became the norm for most vehicles which used both ported and manifold vacuum, providing much more precise control for timing in all ranges of operation. My 1984 Toyota pickup uses one of these and requires the manifold vac line be removed and plugged to check and adjust timing (5 degrees BTDC). Something I learned rather quickly in my younger days using a vacuum gauge to adjust fuel mixtures is that it'll get it in the ballpark range, but using a sensitive RPM tach with a large display (I use a 1970's Sears model) will get the fuel mixtures adjusted much more precisely. I have had to use a vacuum gauge to adjust timing on stock engines which had 2 piece harmonic balancers that slipped as age and miles accumulated. The worst offender was a slant 6. The balancer slipped more than 25 degrees, and living at 30 feet above sea level, I'd adjust for 20" of vacuum after the carb was tuned, recheck fuel mixture adjustment again, then recheck timing. Of course, everything else needs to be in perfect working order to be successful: Ignition system needs to be up to par, zero vacuum leaks, tappets in good working order (if hydraulic) and valves properly adjusted (if mechanical).

[@jeffkellner1585]

Manifold vacuum advance on any good high compression engine always obtain the best results for me ported vacuum just doesn’t make any sense especially with a slightly bigger cam shaft

[@ronsmith7739]

Most car companies all were using manifold vacuum, about 1968 they started using ported vacuum due to emissions and better gas mileage. By 1970 onward they all were using ported vacuum. Only full time race cars would be using centrifugal advance or locked out. For a street car, use a ported vacuum in all cases, even in a "lopey" camshaft because at idle there is no vacuum at all.

[@randywl8925]

@@jeffkellner1585 same here enem with a slightly modified 350. Mild cam and I added a 1.6 exhaust valve into my ported world products heads. I have never used ported. I tried but I couldn't get the idle where I wanted it to be. Numerous vehicles too, not just one engine. If engines died every day from full manifold vacuum people wouldn't use it. I also limited my vacuum advance to 8 degrees. Initial was 12. Total was at 34. Replying Jeff, yes this is an old one but it's always bugged me too. Maybe Mopars respond better that way.

[@540EdgeFlyer]

Hey Tony, Love your videos, and you obviously know your stuff. You do a great job! I have to disagree though with your suggestion of always using ported vacuum for the vacuum advance. An engine needs more advance at light load, and less timing under heavy load. Also, more timing under lean conditions, and less timing under rich conditions. I believe you have the history of ported/Manifold smog era schemes reversed. Looking at a 60's or earlier factory service manual, vacuum advance is always connected to manifold. Consider that the first thing you're always told to do when setting base timing is to disconnect the vacuum hose, and plug it. If it were going to a ported source, this would not be required, as there would be no vacuum at that port at idle. Sometime in the 70's most manufacturers move to ported vacuum, and distributors that were curved to take advantage of ported vac for better emissions. If your distributor is curved correctly... Manifold vacuum is the way to go for street performance.

[@markholroyde9412]

Correct, the "always ported" vac is bollox, all my BB Mopars have run full vac for over 35 years with no detonation.

[@truthandjustice5253]

Totally agree!!

[@Packer1290]

I'm pro ported. I've done it both ways and in my experience the minimal fuel economy at idle along with zero performance or economy improvement at cruise or WOT isn't worth the trouble it causes with idle speed and starting in cold weather. Also I'd add that ignition 101 paper floating around way overstates the benefits of manifold vacuum. For example, If your car is overheating at idle and manifold vacuum is the difference then you have other problems.

[@maliamaxcy7065]

Another well thought out and understandable video, have used a vacuum gauge for years and couldn't explain the process any better. Thanks for taking the time share your talent.

[@chrisbieling1940]

Took me 64 years to find someone who knew what they were talking about,……and could (between spitting, shaking and thinking faster than any Ferrari mechanic,) teach me in four point something minutes, the most valuable, take it anywhere, knowledge that you can get! I don’t care what you wear, Tony, you just gained a believer!!!

[@timspiker9550]

This is the stuff that people need. Knowing this is the difference between being a guy, and being a man

[@robertrandolph6331]

Thank you very much

[@moderateextremist7344]

You keep this up and someone is bound to learn something!!!! Good on ya!!!

[@BeardedWrencher]

Uncle Tony, talk about perfect timing for this video! I'll be taking an extensive road trip soon with an old carb engine and was looking to do a solid tune on my Weber carb before I head out. I had been planning on doing some research on this but haven't done anything yet. I purchased a vacuum gauge from china freight the other day and was hoping to get this done sometime during this week. Wouldn't you know it, you uploaded a video that answered all the questions I had and explained it thoroughly for a rookie like myself who's hoping to keep the carb alive! I really appreciate this video and can't wait to dive into this form of fine tuning myself soon! I'm also gonna be using this method to help my friend fine tune his carb on a 5.0 mustang from an engine swap we recently did on it. Really appreciate your videos! They're definitely better than enough for government work. Hahah. I appreciate your videos and thanks for what you do!

[@kimstewart9152]

Great video! Your knowledge reminds me of my late father who had an amazing reputation for tuning. Thanks for posting this!

[@Westy73]

back in the day my dad had JC Whitney vacuum gauges on all the cars for max MPG. The '70 VW Squareback with fuel injection and the '74 Pinto 4 spd were always neck and neck for best mileage.

[@someguy2741]

60s buicks use a thermoswitch to switch between manifold and ported vacuum based on temperature. This allows full manifold vacuum at cold start and then switches to ported vacuum once warmed up. It also has a trick that when the car returns to idle it switches to manifold vacuum for better idle. All of this is done with thermosensor in the manifold... pretty neat and should be no problem to add to any old carbureted car with an extra temperature sender sized hole available.

[@TorquePowerVideo]

Lots of great info in one video. Thanks for taking the time to make this. I can't remember the number of times I've debated with people about ported vs manifold vacuum advance.

[@Eurostang]

Long time UK sub here. Working on a Buick 215 derived V8 (Rover) which I've de-euro'd and converted to 4 barrel Edelbrock. Just wanted to say I love your videos and you've been such a massive help and pretty much the total source of all the knowledge to do the stuff I do on my channel. Cheers mate!

[@bertramlrezenet9311]

For more precise setting, always adjust curb idle speed and basic timing before adjusting carburator. It is advised to use a tachometer in conjunction with the vacuum gauge for the entire process.

[@markjackson6134]

Thanks, just bought an 84Chevy (350 with an Edelbrock), it ran decent on the long drive back. I pulled the plugs and they're black(mostly) and grey. I will follow your advice.

[@nicksauer6749]

We used to diagnose blocked exhaust with a vacuum gauge. As you raise the engine speed above idle, manifold vacuum should increase. If it doesn't, check your exhaust.

[@ronniecox109]

Also , a bouncy, erractic gauge, is an indication of weak , or broken valve spring(s) . Also use em to make sure that the modulator line to trans has adequate vaccum, not ported vaccum.

[@Heathjham1]

Tony, I used to set my Edelbrock Performer carb with a vacuum gauge after I got it close, also had a kit with a variety of springs, metering rods, and jets to get it really dialed in! One other thing that I used the vacuum gauge to tune on my 389 were the valves! I was running a fairly high lift Crane cam that I couldn't just torque the rocker arms down on like most factory cams! I had to buy a set of poly locks and I would watch the vacuum gauge as I tightened each valve. Once the vacuum gauge started to fluctuate, I would back the poly lock off about 1/4 - 1/2 a turn and then tighten the Allen screw down! When all was said and done, the engine usually idled very smoothly with about 17 1/2 inches of vacuum! Response was excellent, especially after installing an HEI distributor and recurving the timing!!!

[@bobpallang151]

After 35 years of tuning my cars with a timing light (to factory spec) and tach for the idle mixture, this blew me away. I tuned my 66 ford mustang with the vacuum gauge and it made a huge difference. I didn't have to screw around with the timing advancing and retarding to get it just right. I just tuned to the highest vacuum and its done. Thanks Uncle Tony!

[@RJ-vb7gh]

Back in the 1960's GM big blocks, if the engine wasn't worn out, factory timing almost always gave you nearly the best vacuum. I always used a light, but confirmed with the vacuum gauge for fine tweaks. Now to be honest... that didn't always give you the best smog settings. Back in 1981 I took my 1966 Olds (425 4bbl) through State inspection running really well. It literally set a new station record for worst pollution ever recorded on their analog instruments. It was so bad that they stopped the inspection line and let me re-tune the engine while hooked up to the machine. After a lot of fast tweaks the car passed for 1981 pollution standards... but man it ran like crap. On the up side, it did get better gas mileage. So keep in mind... best vacuum doesn't always mean best pollution... nor best gas mileage. And yes, I know it should, but it doesn't... Also, with the vacuum gauge, you can tweak an engine to run best on different octane fuels. By 1981, it was getting hard to get Sunoco 260, 100 octane which my engine was originally tuned for.

[@RJ-vb7gh]

@@moparnut6286 I'm in NJ and it was at the Livingston inspection station... in the drive in theater... that My Olds was being inspected. When they stuffed the tester into the tail pipe... pandemonium broke out among the workers who all rushed over to see the highest readings ever recorded on the old analog gauges... "I can fix it" I told them while they pointed and cracked jokes... So I got my tools out of the trunk... while the line of cars behind me backed up onto Rt 10 and I adjusted the idle screws, and the timing and made other adjustments while the guys watched the meters for improvement... and made recommendations... like take off the air cleaner, pull the PCV, turn up the idle, etc. It was rather bazaar, but I was grateful because I didn't have a pollution meter which at the time cost thousands of dollars to work with. Finally the guy at the machine says, that's as good as it's going to get. And when I asked if I passed... He said, you passed for 1966 5 minutes ago... you actually passed for 1981. (which was actually a catalytically converted standard and my car had no such converter) In any case, I had to do several adjustments to get the car running well enough to drive home after that. Buy yes... My 66 Olds, 73 Buick, 84 Plymouth, 92 and 94 Saturns don't need inspection in NJ and all but the 94 Saturn are either tagged antiques or on collector insurance. Unfortunately, I've got to find the dang evap leak by next year to pass inspection for my 02 Ford.... I truly hate new cars.

[@frederickbooth7970]

@@RJ-vb7gh That was very decent of the inspection station to allow you to adjust while hooked up to their meter. Here in Oregon we bet they would not allow it.

[@RJ-vb7gh]

@@frederickbooth7970My car failed so spectacularly that the entire inspection staff came over to see the machine readings... They said they didn't even know the machine could read so high. By that point everyone working there was invested in seeing how low the emissions could be tweaked down to, while they made suggestions. When I asked if I passed the guy said, "You passed 10 minutes ago for a 66, but now you pass for a brand new car. (circa 1982)" That's pretty much when I realized that all of the smog stuff and the catalytic converter didn't do much of anything on a car that was tuned properly. If your engine is burning clean... there's not much for the smog stuff to do. To be fair... once tweaked to ace emissions, the car ran poorly, I had to undo a couple tweaks to drive the car home. In the end doable wasn't optimal. But no... that wasn't the inspection station extending me a courtesy, it was more like them exercising their curiosity. Pretty much any car with with a carburetor and and an independent ignition system can be tweaked to pass pretty much any smog test if it isn't smoking. And if it's smoking... you bring it through after dark in winter when the inspection station is open late... I had to do inspection 5 times until it got dark early enough for me to pass another car. And even smoking... it passed the machine test, just no one noticed the smoke.

[@akallio9000]

This used to be standard information in the repair manuals back in the day.

[@jamesbetts3371]

do you mean when Chiltons Manuals were actually well written and the standard in most ROP and shop classes, back when a snap- on Calendars were printed for men by men with beautiful women with great bodies and happy to show it all tastefully. All the while showing off the tool of the month.

[@legitdelirium3446]

Don't take this the wrong way but I appreciate that you upload your knowledge to KZbin. Because when the day comes that you pass people will still be able to learn about working on this "ancient tech"

[@ethanbunch3274]

Returning to this video after a little while a lot smarter. Your videos have really helped me build my car knowledge and in fact I'm about to throw a carburetor on my 1991 F-150! The engine is shot so I'm throwing a 19 86 engine in it and a carburetor swap will just make the wiring less of a hassle. I also bought a vacuum gauge a while back and I've used it to diagnose so many issues with my engine I have you to thank for this. I'm also throwing an Edelbrock on there which is the first carburetor I ever rebuilt so I really wanted to thank you for really helping me grow. I look forward to using all of this advice on an actual running engine instead of an old carburetor sitting on top and intake in my garage!

[@ArchersGearheadGarage]

should do a demonstration on erratic vacuum readings and valve lash

[@brucesherrill4116]

I agree. I have a stock 77 Dodge Aspen with a 318 with 87,000 original miles and I hear a little puff puff every once in a while out the exhaust. The vacuum gage reading is lower than I expected (around 14ish) and bounces back and forth about ten inches of vacuum in that 14 inches range. The chart I looked at said bad valves. Hate to tear the engine down if it’s something else.

[@gg5115]

@@brucesherrill4116 Well, technically, just pulling the heads off is not an engine teardown. I've done that to a few engines, and sure I'd like to rebuild the whole thing, or at least hone and re-ring it. But you can only do what you can do sometimes. Especially under a shade tree in somebody else's driveway... You can fix that for the cost of head gaskets, intake gasket (which is almost optional) and a valve spring compressor. The screw on kind are not that much. After you've taken a wire brush and carburetor cleaner to the heads and made them shiny, stick a valve in, chuck the stem into your drill, and holding the valve tight in the seat with your other hand, spin and grind the shit out of it. You can get a decent valve job that way. Use plenty of grinding compound, and a slick oily rag will help keep your holding fingers from getting burned. Oil each guide first. Keep track of which valve went into which seat. Pulling against a drill will ruin it, you have to push with your other hand.

[@bannockchief]

@@brucesherrill4116 I think AGG is talking about a lopey cam with little overlap at which point I would suggest running it rich, but lean enough doesn't load up if you don't drive it appropriately. However, replacing the valve seals on you 318 may reduce you erratic vacuum. If you have good and even compression, maybe burn a little oil, and the manifold gaskets are good, then worn valve guides and bad valve seals are likely the culprit. You can also tell if they are bad if you pull the valve cover and instead of the seals you see small pieces of plastic in you valve springs then they are gone.

[@markusgarvey]

It means it usually means your guides are worn, or if you have solid lifters you have them set wrong.

[@evanc6110]

Back to the comment section Uncle Tony, very nice!

[@ericgreen7618]

Awesome no one has explained metering rod springs like you that actually makes sense and I understand totally but always love more vids with old school knowledge and tricks 👌

[@anthonydownes8769]

Another great video uncle Tony really enjoyed watching it and learning some old school ways of turning your car regards Anthony from down under

[@bannockchief]

On anything without an ECU I advance the initial timing to the point where I can take off in 2nd uphill and not get pinging. If I have a timing light and want to set up the whole curve, I start Ford's and Chevy's around 30 to 32 total advance and mopars at 34. I then drive it and adjust the advance plates to feel, and again under load, with no pinging.

[@craignehring]

Nice, how to know about vacuum gauges

[@johndorflinger2344]

Not the whole curve, just centrifical + base.

[@joecarter6491]

Ok i cant let Tony's comment go......it takes WAY more than 2 screws for government to work in fact at last count it took several dozen screws and a think 2-3 cans of lube spray....4 maybe see i'm screwed up now AAHHH!!!

[@MrTheHillfolk]

You forgot that if those were 2 government screws they probably cost about $3567 a piece depending on shipping , for mild steel.

[@joecarter6491]

Those would be defined as screwballs

[@jamesbetts3371]

@@MrTheHillfolk and still not work correctly

[@MrTheHillfolk]

@@jamesbetts3371 you have to install it upside down , probably.

[@oldschool6345]

Lol

[@charlierhiger7478]

You know more about how to time a car than anyone I have ever known. And I have been around car mechanic's my whole life. Thank you!

[@skyline289]

cant thank you enough for your time and efforts you put into making videos, i watch them everyday as i eat dinner!

[@heavychevy2289]

Would love to see the results on a choppy cam💪

[@Mynextproject_74]

I'd like to hear more about ported vacuum VS manifold vacuum on the vacuum advance.

[@Ltmonte]

Clelan Sametts it’s all the same except at idle and WOT (wot has no vacuum anyways so it’s a moot point). Manifold has timing advance at idle, lower EGT’s and not as good emissions, then pulls timing as the throttle blades are opened. Ported vacuum has no advance at idle, because it sees no vacuum at idle. As the throttle blades are opened, the vacuum rises and it adds timing advance. The way that you determine which is best is the way your distributor curve is set up, and your application. Some guys will swear by ported only, others by manifold only. If you have the ability to use a dyno I’m sure there’s a negligible difference in part throttle power, because in the middle of the part throttle operation, with the manifold vacuum advance dropping and the ported rising, they intersect at the same amount of advance. So, to sum it up, they achieve the same effect, just one adding timing and one taking timing out. The engine will run differently on each due to the way they add or remove timing. Remember, this is only idle and vacuum cruising, wide open throttle doesn’t matter for vacuum advance.

[@GlamStacheessnostalgialounge]

Check out Thunderhead289, he practically has a PHD in manifold and ported vacuum.

[@jimifed2798]

@@Ltmonte Joey. You should have a more thumbs up best answer I've seen it really is your distributor curve that seems to make the difference.

[@mattbauckman9907]

Joey Montemurro More advance at idle DOES NOT produce higher EGT, it lowers it. Other than that, you are spot on. Depends on how your particular distributor is curved.

[@lskiller1903]

Let the ARGUMENTS START!!!!!!

[@softenerguy]

Tony thanks for bringing up the manifold/ported vacuum point. And also the 70's vacuum hose nightmare, always fun cleaning those up under the hood! Love your channel dude!

[@brettavery7463]

Fantastic info - great to see you passing this info along to the next generation of tuners! Some of us never made the switch to efi 🤔

[@loganshotrod4x464]

I’ve always set my timing by manifold vacuum, with the vacuum advance disconnected, and backed off by 5 inches of mercury to account for ignition advance under acceleration and higher RPM. With a performance engine, I found that I had to back off the timing just a tad more to keep it from detonating, pinging and make it easier to start, but it usually isn’t by very much. Setting timing with the timing light was never really an option for me because the engines that I had used aftermarket camshaft, various different compression ratios and everything else was pretty much is thrown together so I really couldn’t set timing with a timing light according to any recommendation.

[@UncleTonysGarage]

And that's why you set timing to total and let initial fall where it will. If more initial is needed, time to curve the distributor and narrow the advance range.

[@rucus0101]

@@UncleTonysGarage If you have a large cam you can also use your manifold vacuum for the vacuum advance. If will pull that idle timing forward a bit for a smoother idle in a large cam situation. On stock engines they used ported vacuum because the advance would be too far at idle and you would be making NO based emissions they didn't like. When you have a low vacuum from a big cam the manifold vacuum and a very quick short advance curve helps a lot.

[@colemanadamson5943]

I remember the good old days when one could start the car with a screwdriver on the solenoid.

[@89StarquestTSi]

Yeah because that energizes your ignition coil too.......

[@freakbiker]

Thanks Tony, watched a bunch of other videos and by far you explain it clearly and without talking as if your audience are pros

[@knightrider1977]

Love the comment about the vacuum routing of the 1977 T-Bird. That bird happens to be my daily driver right now and I know exactly what you mean. I had some vacuum issues and had to bypass a lot of those heated routes and return the carb. Still debating if I want to correct things or leave it as is. After setting the idle mix, RPM, initial timing, etc, its a lot more peppier than when I first bought it but a lot of room for improvement. Hopefully in the spring. Thank you for taking the time to pass on the carb knowledge!

[@markrahner2065]

"Fine Engine Tuning" - of course it's a fine engine - it's a Mopar.

[@drlong08]

@3:44 "It's close enough for government work.." As a guvinment employee, I can attest to that.

[@chasmontecarlo7271]

Uncle tony, great video very informative learning more all the time from you I will be starting my montecarlo soon now I can really tune it right thank you. 👍🔧

[@mikegreco8451]

I love these videos. This is knowledge your not going to find in many books. Keep the videos coming.

[@gmstudent93]

Thanks for the good info, can you do a video on diagnosing engine problems with a vacuum gauge.

[@CelloandAnayaJ]

I was thinking at first you could kind of tell he was legit by the way he was holding his cigarette….but once he said “was that right, well it’s close enough for government work” I knew he was.

[@TheChris1299100]

This video really helped me tune the Edelbrock carb on my Jimmy. Thanks for posting informative vids like these!

[@oldschool6345]

Another great video. You should consider showing how you use your other senses. As an old schooler I know you already understand but for the guys learning simple vacum tuning there would be a huge advancement in their understanding. The old guys that told me "yea but listen, do you hear it?" or "do you feel it?"...."did you smell it"...usually requiring a repair in order to properly get it tuned. How many times were we told "it needs a tune up" but it really needed fixed. Your explanations are simple and exact. Thanks for sharing

[@hank1556]

Uncle Tony can you vacuum tune the government? my taxes are too high

[@ScottKenny1978]

You want to increase the vacuum in your bank account? 😆😂

[@thromboid]

Such attempts are usually overwhelmed by the prodigious supply of hot air. ;)

[@maxyundt8202]

I thought ported vacuum advance was something that cars in the 70's used to try to improve emissions, not manifold.

[@UncleTonysGarage]

nope

[@jakebullet8990]

@@UncleTonysGarage That's an argument I can't find a answer to. My 67 Pontiac Tempest uses manifold vacuum from the factory. I've tried setting it up ported and it runs better on manifold.

[@skipsgarage9297]

My 1969 400 pontiac runs better on manifold vacuum also. Depends on the engine, do what works best for you.

[@ramblr1959]

Gm cars used manifold vacuum up until the 70’s when they switched to ported to raise exhaust temps to help burn off more emissions. I had a 1968 327 in a truck that always ran hot when set up with ported vacuum. Switched to manifold and temps came down and off idle power was way up.

[@maxyundt8202]

@@ramblr1959 exactly, ported was just an emissions bandaid

[@brianhyslop2015]

Thank you SO much! I was about to take the insurance off my 81 Malibu because I could not rid it of a off idle stumble!! Would stumble at cruising speed and for a moment when leaving a stop sign. Lost my pops to Covid last year and don’t know any old school guys that know their way around a small block. Went out after work with vacuum gauge after watching this video last night before bed. RUNS SO BADASS NOW!!! Driving it to work tomorrow

[@petermajkovica3700]

Thanks uncle Tony, I'm learning a fair bit from you, keep it coming... 👍

[@patrickmitchell100]

Isnt this just general knowledge they teached like in high school shop or am i just that old 😳

[@BigHatsince98]

Shop has been gone since about 95 where I was. The kids knew more than the instructor in my class. He hated me!

[@bjodaddyo]

Today's mechanics don't know what a carburetor is. Much less a timing light. Not a bad thing, just showing how old we really are. ✌

[@cliffbennett3372]

It's definitely a bad thing. Lol

[@steveveness3829]

Yeeeep almost 60. 43yrs trade life, I watch a fella tune carbys and listen to them. Makes me sick knowing how much he charges for what he gives them. I did a 383 chev on Friday. Has a 411 Edelbrock on it. It flys now. The man who owns it, has owned it for well over 30yrs, and swears blind it has never gone so well. Swears blind it has never fired up istantly from dead cold. Maybe I am made different not sure. I admit I had to go look up how edelbrock carbs work, because It's so long since last I tuned one. Thank You Tony for your imformation refresher course😊

[@Heiguiking1777]

my friends father in 1981 could do this all by ear and feel didnt need a light or vacuum gage lmao dude had your truck or car dialed in after 15 minutes of fucking around under the hood miss that old dude knowledge

[@smokeysmishaps4214]

You can blame the engineers for changing all this, including amount of electronics that run the vehicle compared to older cars. Not a bad thing for new technicians like myself. I just started 5-6 years ago. Just more things we need to learn on top of all the modern technology. I always love a challenge to learn. If only we can go back to these days🤣

[@sategllib2191]

​@@smokeysmishaps4214government regulations created all this lol

[@garydesbois5415]

Great video Tony ! I forgot some of those things from my teens. What a great refresher !! 👍👍

[@ibnalfreak]

Great video, always enjoy watching and learning something new.

[@jds1906]

2:28 did he just break wind?, he better check his draws, sounds like bad back pressure, lolof

[@karlbishop7481]

Tony, I wish you and utube had been around years ago. When I got poor I got stuck with early 70's Chevy truck with a 350. I put an 600 cfm Holly on it and with a Holly book I got pretty good at tuning it, power valve, jets, secondaries spring etc. In later years I built a 360 Duster with hot cam,porting, balancing and all kinds of good stuff. Anyway I put an Edelbrock carb on it mainly because it looked good with all the polishing and original look. I used it out of the box which I know I shouldn't have done but I knew nothing about how to tune it. I couldn't find much info on how to tune it either, before all this good stuff on the net. I have always regreted not puting a single plane with a Holley on it because I knew I was leaving a lot on the table. Keep up the good work. Mopar or Nocar.

[@81eagle]

If you find yourself with power valve that is unknown and you don't find any markings on them you can test them with a Mityvac and the umbrella attachment. Great video as always Tony!

[@keithodell6426]

Thats how I LEARNED back in the day! Thanks to you!

[@themetalgator6668]

Thanks so much Tony. It's crazy how helpful these videos are when you actually have a car in front of you to immediately apply the knowledge too. This was helpful to my buddy and I working on his 85 mustang. Thanks again

[@charleysgarage]

My Uncles name is also Tony and he is an automotive tech (retired) and he would be proud to see this video. Great job!

[@pauljconroysr4080]

just watched several of your vids excellent discussion and break down on everything :) simple easily explained and direct with out dumbing anything down !!! PLEASE PLEASE KEEP UP THE GOOD WORK :)

[@jpeagle21]

Great information. Great teacher. Thanks for taking the time to make this video. It will help a lot tuning my car.

[@rtchrg440]

Fantastic info Tony - especially like the AFB metering rod with covers off when running tip!

[@dbeaumontresident847]

Tony is pure common sense. Fact! Love your vids Uncle Tony & Kathy!

[@RDC_Autosports]

i’m 38 my dads like this guy we have a machine shop still building race cars... carbureted still... i remember in the 80’s we had a oldmobile station wagon, it had a “fuel economy” gauge in the cluster i said how’s that work? he said vacuum and he smashed the gas it pegged over then came full back to the (+) side and he explained how it worked the more vacuum, the more the butterfly’s are closed the less fuel the more open the less vacuum and worse fuel idk why but i thought that was the coolest thing

[@veraciouspatriot4297]

What a great series of videos! Glad I found you, and thanks.

[@throttleblipsntwistedgrips1992]

Continuously grateful to the legend thats helping me keep my mopar running like a top. Much love, UTG.

[@Mrnicguy00]

Yes! Please do another vid on this. I went to college to be a automotive/marine tech and not even they taught this. My brain desires more knowledge, need input! Great stuff, keep it coming my friend.

[@kevkilian]

Keep it coming Tony! Helping me learn every day!

[@SolaFide802]

I really enjoy and benefit from your relaxed yet detailed tutorials. Thank you

[@SolaFide802]

I am working through a new to me 60 Impala that has a 350, camel hump heads, performance cam and newly installed Holley Street Avenger. Car idles terribly, transmission won’t kick down and I don’t know if secondaries are kicking in. I don’t know what this engine came out of so many mysteries

[@lonotiki]

Thank you so much ch for your videos. Completely thorough and you give me the confidence to work on my old wagon .

[@georgehebb9806]

GREAT JOB Uncle Tony. I wish you where in my area. I've allways tuned carbs by feel and sound but know I will try the vacum way. Thanks again.

[@codygardner9536]

The video I've been looking for. Do appreciate you getting right to the point.

[@tehagent1321]

Thanks for this video. I have a 66 Polara that has one of those finicky Carters on it. I'd been fiddling with it without a vacuum gauge for quite some time - trying to get the idle right, the exhaust to not smell rich or lean, and have it run smooth down the highway. I damn near had it by nose and ear, but the vacuum gauge was the key to getting it perfect. I was a tiny turn off on the idle mix - like not even 1/4 turn, but it made all the difference.