Classic Car Tuning Problems - Curing Off-Idle Stumble, Bog, Hesitation, Stall And Backfire

The most common question we get during our Wednesday Night Tech Talk Live shows has to do with carbureted engines and poor off idle and low speed performance..
Assuming the engine is mechanically sound and not made up of a crazy mix match of components, nearly all of these problems can be traced to either carburetor accelerator pump or initial ignition timing problems.
#automobile #diy #classic
Here's how these systems work, and all the information you need to troubleshoot and correct these problems on your own engine.
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[@chrisallen766]

I'm watching this to fix a problem I had 40 years ago.

[@Szamuz]

And it's already fixed

[@moss8448]

same here, I put a Mikuni on an MGB and it would do this stuff so I just put the SUs back on boy was that a bummer Mikuni, remember looking to see what happened when you 'showered down' didn't ever see that squirt of gas...grr. It was new out of the box too.

[@termonostruman]

seen a car with a sticker sayinG.- I LOVE CARS MORE THAN WOMEN in the rear I CHANGED MY WIFE FOR THIS CAR. and in the door: I kiss my dog not women,, well i can make an exception and kiss this car.

[@deanberolzheimer2658]

did you marry her?

[@termonostruman]

@@deanberolzheimer2658 I HAVE STIKER IN MY CAR: I kiss my dogs not women,, well i can make an exception, and kiss this car.

[@htautomat]

Tony is the single most important source of knowledge for the classic car owner. End of story.

[@puttsr]

Dealing with this right now. My car wouldn’t be running if i wasn’t watching this channel. Shop told me i needed a new engine when after watching tonys videos i discovered that it was a fuel issue. Replaced lines and new carb and never looked back. Thanks.

[@jonmoore8995]

Really good Master Tech video UTG.

[@benjudy4406]

You may think a 30min video is expansive but I find it very informative and I learn something in everything you post. Thanks for taking the time to share your knowledge.

[@gtproductions0109]

#uncletony'sgarage THIS VIDEO BELONGS IN THE SMITHSONIAN!!! At between 6:00 and 6:49, brought my 38 year old self back 20 years to a G body build I did, crank and crank and crank no start. After 1am I realized I wired the fuel pump wrong and my 383 jumped into life 😅😅😅 🤘🤘🤘

[@SweatyFatGuy]

We all had to learn carburetors, its just that old guys like Tony and I learned it a long time ago, and younger people are learning it now without the massive wealth of information that was in magazines 30-60 years ago. Young people have the internet, and its full of people who have no freakin clue but tell it like they know what they're talkin about.

[@dddevildogg]

You mean there's BS and nonsense on The Interwebs? NO,can't be.Who would do that?

[@robertdinicola9225]

I only used holles on cars but, i mastered jetting and tuning motocycle carbs.

[@robertheymann5906]

Amen to that brother... I'm appalled at the Facebook engine build groups that sling so much B.S. Unfortunately many self admitted young first time builders are asking questions and getting answers that just thicken the confusion. I'm no pro but at 62 years old I've learned how much i don't know. Guys like uncle Tony, Ben Alameda, Eric Weingartner, David Vizard and a few others are real teachers who i try and steer the new guys towards but I'm afraid many never get there. "How to hot rod your sbc" is priceless but books are viewed as ancient. Teaching is sooo difficult

[@SweatyFatGuy]

@@dddevildogg I know right! Just found out myself!

[@JudgeMeNotLeMans]

Us well aged hot rodder’s also had the added benefit of having more well aged (dare I say vintage) hot rodder’s to learn from. Thankfully I didn’t think I knew everything when I was young… and soaked up as much knowledge like a sponge as I could. My dad forgot more than I’ll ever know.

[@Sonormuseum]

I really wish that the internet, KZbin and Uncle Tony were available to me 40 years ago when I was in my 20’s and had my ‘65 Dart and ‘67 A-100 van. I know and experienced exactly the things you talk about in this video. It was maddening. Especially on the A-100 (318/auto, I wish I still had it). The timing light told me one thing, but it ran best when I adjusted the distributor by hand to where it liked. It all makes sense now. Hopefully, I can, one day before I’m gone, have another “analog” Mopar to tinker with and enjoy. Thanks, Tony. ❤

[@tonyb3864]

Good information for someone who is new to carbureted engines. Or refresher course for us old guys.

[@archieguitarz4700]

Want to add, to much pump shot can cause hesitation as well as to little. It's all about finding that happy medium.

[@sprocket9200]

So much knowledge and experience in this one video would've taken me months to discover the hard way, like I did lol. Thank you Tony for carrying the torch

[@tylerdavin1555]

Thank you so much to you and the other folks being patient with us! At 40 I finally was at a place in life to buy a 76 ford pickup. I always wanted a 6th gen ford which my grandpa and I used to buy as a kid. I’m now trying to learn these things you guys know as just common knowledge. I’m finding myself pretending to know things people say “well obviously” about.

[@chipwright6193]

Those are great old trucks! I'm about the same age, I grew up driving my parent's 79 F150 and now I daily drive a 73 F100. I love how simple they are to wrench on.

[@JDWorkshop-wn9tt]

Good old tech is way more interesting than modern computer tuning!👍👍👍

[@nicholasagnew2792]

I know you'll agree with this, many people will claim that manifold vacuum advance is better, yes for decreased exhaust temperature, but I've always found that for performance ported vacuum advance is better. My experience in industrial big block tuning says with manifold vacuum advance you may experience an off idle stumble and I'm absolutely sure that is the case for many many other engines.

[@autonomous_collective]

DIESELING ENGINE: This can caused by a number of things: 1) Too fast an idle speed. 2) Too rich fuel mixture. (Long-term causing carbon build up which glows hot and ignites fuel after the ignition circuit has switched off) 3) Too lean a fuel mixture at top end from incorrect jetting or airleak, casuing the engine to overheat. The fuel/air mixture could be heated to the point that it self-ignites, causing the diesel run-on effect. 4) Timing is out. The timing itself won’t cause the run on as the ignition is switched off when the run in occurs. However timing too far advanced can cause an overheating engine which can attribute to over-run. USUALLY its this. Should have made this number one. 5) Lower octane fuel could aggravate the problem, because it will self-ignite quicker than a higher octane fuel. But it alone won’t cause the problem. 6) Carburetor idle stop Solenoid . 7) Sparkplugs have a temperature range. Are you running the right ones for your engine spec? Also are they clean and gapped correctly?

[@HeadFlowInc]

The proper adjustment for a Holley accelerator pump is .015”-.018” clearance with the throttle held wide open. The clearance prevents pump diaphragm damage and full pump volume. Be careful adjusting the accelerator pump, it’s easier than expected to damage the pump diaphragm. Tom Vaught Holley engineer

[@billybobholcomb8768]

Always great information. I grew up with carbs and I still learn great stuff from you Tony.

[@ThomasA63]

Tony, true story.. Its been about 15 years ago now, I was working on my 70 vw carbs at the shop I was working at. At this time a man I knew brought in a guy my age who'd just graduated the local universities automotive program which is recognized as one the best in the country, he actually graduated the program with high honors. Well he had seen me working on my carbs and he was absolutely amazed and told me he had no idea how carburetors worked. I asked him, if you just graduated the auto program what were they teaching you? And his answer, fuel injection.. electronic fuel injection was the only thing taught in that program, they didn't even touch base on carbs

[@Matthew-r1w7c]

Sad waste $ going to school then

[@Tk-ou9ec]

I used your power tuning method on my mild 318! I saw that on an older video of yours. So I don’t know what my timing is set at but it sure runs good! Also,I’m running a tuned Edelbrock 500 and after experimenting I found mine runs better using manifold vacuum. Quite a snappy set up now. Running a Comp 268 cam, Edelbrock performer intake, hei distributor and coil and a full 2.5inch exhaust. My biggest improvement was upgrading the diff ratio from 2.92 to 3.45. By far better now.

[@SchoolforHackers]

Sweet.

[@nickbonvino]

Great video once again. Couldn’t be explained any better. My distributor was seized . Once I freed it up and advanced my timing all bogging was gone and tires were spinning joyfully!!

[@pmscalisi]

The title of the video sounds like a car I had when I was 17😂 Great video, Tony, there aren’t many of us around anymore

[@l77scmaro2]

The way I find true top dead center without a piston stop or a degree wheel is similar. Bring 1 up to close to TDC compression stroke get long zip tie (or something that CAN NOT fall into the cylinder). Continue to turn the engine clockwise (normal rotation) until you feel the zip tie stop moving up. Mark the dampener (I use 0 on the timing pointer). Now continue to slowly turn the engine clockwise until you feel the zip tie start to go down and mark the dampener again. True TDC is at the exact mid point between these two marks. I go back and repeat this a couple yours because I'm neurotic like that but this has the fastest, easiest, and most precise way I've found to to locate TDC without tools. Obviously a degree wheel and piston stop tool is more accurate but this way gets you really close. And don't be surprised if your pointer doesn't exactly point at the mid point between marks which is true TDC some will some won't. If it's significantly off your dampener has slipped and needs replaced. What you're doing is finding the mid point of piston dwell at TDC.

[@jerryakbar6147]

In queens we used to get a guy in the car put it in drive with the break smashed down, the guy under the hood would turn the distributor until the the tires started to break traction. Lock it down and your ready to go.

[@Z_732]

@jerryakbar6147 lol.. old skool stuff is still viable. Maybe not "right" but can get you in the ballpark. Cool story jerry

[@Z_732]

@jerryakbar6147 another old redneck way... is listen to the engine at idle. If it's hitting correctly, (just under the rattle sound). Just rev it to 2500 ish.. turn it back and forth until happy.. adjust depending on application. That will make it run. Not correct.. but a good base point. Until fuels change of course. Lol

[@karlbischoff5181]

Thanks!

[@petesfeeder]

Being an experienced engine tuner is much like being a great lover. There is science to it, but at its best its a mystical intuition.

[@greenbassboosts8872]

Yeah the go button is generally in the same spot but a little different each time eh?

[@spankyham9607]

I am glad to hear you clarify vacuum advance timing based on manufacturer because everyone says one or the other and get into their camps as to why and I am so glad to learn things were based on manufacturer.

[@samueltorres7555]

Min 14:10 + gold. Lots of arguments about ported or manifold explained right there. As an example. Msd vac adv requires ported per the manual. Thanks, Uncle Tony, great way to lay this bs to rest.

[@johnkelly8525]

You can use the sliped balancer simply by remarking it with a white marker that will work short term

[@WalkerSmallEnginePerformance]

I manage a group of forklift dealer service departments. We hire young guys out of trade school and they've never seen a timing light or adjusted valves. What's worse is most of them don't know how to use a multi-meter or scan tool either.

[@FrankF-vp4pt]

Good video Uncle Tony. I agree on power timing being best. I'd start out advancing distributer as far as possible to the point of starter telling me it wasn't happy. Then I'd brake torque car and listen for ping. I'd back it down to the point of not pinging then take it for a ride and finish adjustment after testing under load 4-5 times. Always had my wrench to snug distributer once I found engines happy place.

[@Z_732]

20:07. While yes I agree.. it also made sure the distributors vacuum advance functions were all working correctly. If you did all this and still had issues.. put a timing light back on it with the advance hooked up and rev it up a little to make sure.. basic stuff to us.. but thought I'd share just incase.

[@Blizzard9500]

Accelerator pump, timing AND I see a lot of guys running way to lean, this also causes the same issues. I have changed jets on hundreds of carbs for friends that had no idea how to, or even thought of jetting a new out of the box carb. They just buy them, bolt them on, then wonder why the car runs poorly.

[@howardwayas8000]

Thank you. This is what I visit your channel for. Older mechanics looking out for younger mechanics is what our culture is about. Younger mechanics have an interest in older tech with less electronics. Plus it's awesome seeing and old car or truck still on the road.

[@freedom1garage]

Great advice on the newer dial back lights. We purchased a HF model… 4-5 degrees off. I’d add that if using a light, after setting timing with vacuum disconnected, re-connect the vacuum line and watch the strobe as you blip the throttle. You should see the dampener mark jump ahead. This will also verify what the type of distributor and if you have it connected to the correct type of vacuum source. Jumps ahead- good. Jumps back- your distributor wants ported and is hooked up to manifold.

[@keithroute8906]

Nice job Tony, that will help a lot of people. You have amazing knowledge. I get cars other shops have looked at and could not get a stumble out of. Yes, carburetor or ignition. I also get Frankenstein motors in cars bored, stroked, over crammed, over carbed, etc. etc. Also odd swaps, especially GM’s like say a Chevy with a Buick motor or a Pontiac with an Olds motor, just about anything. Yes, if the accelerator pump is working and adjusted properly, most likely ignition timing or an ignition or electrical problem. Might be just me but I have repaired and adjusted many rotten carbs causing stumbling that had good accelerator pumps. A Thermoquad in the distant past comes to mind immediately. Like you perfectly stated, it is nice to know when something is good, like known good carb or known good ignition before someone changed the carb or whatever they did. I will give anyone a tip on a stumble I found. I get a hot rod in, barely touch the gas and it stumbles, mash the gas, it either takes off like a race car or it drowns and dies, it had been around to a lot of shops. Customer said he bought it that way, said the seller thought it was the carb needing adjustment but he had been driving it that way for years. I could see someone had been all over the arm bending for the accelerator pump but it appeared to be working well. So I am thinking ignition. This is a very old hot rod with some kind of replacement 350 with a cam, aluminum heads and manifold. I see it has a chrome timing marker and this thing is tiny and although true to top dead center on the zero mark was not spaced/marked correctly after that. Was not the problem but could have been. The problem was the 12 volts going to the distributor was keyed voltage and weak. At idle the engine is spinning the alternator the slowest giving anything and everything the weakest voltage it will get. I find it has an all out race ignition and it needed voltage as high as it could get. The resistor wire had been replaced with a nice thick regular wire. It was a half volt low, motor running or not, reving up or not. Keyed voltage was low anywhere, all the old fuse system was intact. The fix was to use the keyed voltage to run a relay to hit the high performance ignition with fused full battery power and it turned that stumbling, spitting dying thing into a tire fryer. The cam seemed big so I timed it to vacuum first. Then I took a piece of masking tape and taped it over the timing mark indicator on my 350 and rubbed in the marks, transferred that to customer motor indicator lining up the zero marks so I would know where it actually was set. It was a lot of timing, I took just a smidge more out. Anyway, that fixed it, slam dunk on the tune, the motor ran like a race motor, snappy, pulled hard, tested good, didn’t want to break anything. Very happy customer when he left. A rare problem but I have run into that type thing a few times now so hopefully that may help someone with a stumble.

[@halseyknox]

Todays era just use a computer to solve the problem.....rather get my hands dirty and do it myself....glad there are guys like me still around....UTG👍

[@crautoguy8384]

I've gotten turned around on tuning cars with accelerator pump problems it's just like the mechanism in a spray bottle like Any kind of spray bottle like Cleaning products windex come in or any kind of just bottle you fill with whatever same kind of mechanism If you pull the trigger you don't have a good solid squirt. I was always taught that it should be a clean spray throughout the throttle movement not A Half Squirt and then a dribble. Also need to make sure that the fuel bowl is full when you're checking this cause you cant do it a bunch of times and get yourself turned around because there's no more fuel in the bowl than the engines flooded and it won't start but anyway I hope you get my point I love this video Tony. This is the kind of stuff. That was lost in the generations after you.

[@michaelramzi1094]

There is always something with carburators. The time is passed on them, however, I have a mustang with autolite carburator. Pain in the neck.

[@s.a.f.r.a6403]

Uncle tony I'd like to correct you on the fact that Motorcycle CV carbs do infact sometimes have a acclerator pump they get used on scooters, mopeds, superbikes and even harley used them on their Mikuni CV carbs for better throttle response they can be tuned aswell

[@jasonbusch3624]

You are correct. Most newer 1980's and up 4 stroke motorcycle and atv carburetors have an accelerator pump. Most 2 cycle carburetors do not.

[@s.a.f.r.a6403]

@@jasonbusch3624 they can be handy and a pain when they decide to not function as intended rich mixture conditions or as uncle tony said a stumble or stall off idle circuit

[@jasonbusch3624]

@s.a.f.r.a6403 I started working on motorcycles back in 1991 and have worked in shops my whole life. I have a ear for lean conditions and engine problems. My buddy stopped by on his Harley and I told him it wasn't running right. A week later he stopped over with it and it had fouled a sparkplug and was only running on one cylinder. I checked compression and spark it was good so we put a new sparkplug in it and it lightly smoked out the exhaust for about 15 minutes, but was running great again. The old sparkplug electrodes were really wore and rounded, had a lot of miles on them.

[@apocolypse11]

People like Tony an his followers fail to realize new motorcycles two stroke or four, have carbs or efi as options in modern times. But they claimed old school lol. Also a tiny 150cc modern dirt bike has a bigger carb with more airflow that a slant 6 3.7liter single barrel carb. Pilot jets,main jets,leek jets, needle position,accelerator pump adjustment in modern KTM or Hondas etc is not old school they make them brand new in 2024 or efi of u want.

[@s.a.f.r.a6403]

@@apocolypse11 worked on both newer stuff easier to work on older stuff fights back

[@sasz2107]

I remember reading all of this in Chilton's manuals 30 years ago on how to tune up your car properly. This type of knowledge is becoming lost because so few of us drive cars with carbureted engines anymore. One comment. On a Slant 6 you can't advance the base timing very much. I believe it's because of the long stroke the engine has. On most engines you can advance the base timing a lot and you're fine. On a Slant 6, in some years in the 70s, the spec was top dead center. You could advance it 4 or 5 degrees but that was about it.

[@davidkraus5221]

So much gold in this one video! What solved my issue was using a quality rebuild kit. The rubber on the auto parts store accelerator pumps is crap and as soon as I had a good pump in the carb it was fine.

[@HarleySLA]

HNBR is where it's at. I don't know how many kits make use of it, but it's like rubber on steroids. It's the bomb, I use it anytime I can, over rubber.

[@nicholasagnew2792]

In a downdraft Weber the transition "slot" is fed by the idle jets so don't listen to anyone telling you the idle jet doesn't effect driving. It will cause a major stumble at mid to high rpm.

[@frankr3251]

ikr 💯 I learned this the hard way. I kept hearing that as soon as you crack the throttle it's off of that circuit but that's simply not the case. It has a major effect off idle

[@Videoswithsoarin]

same story with the side drafts

[@SE-me2pt]

Unmentioned but important. Many of these supposed issues are non-problems that can be made mitigated by pedal usage/and understanding your particular combo. Unless you grew up with carburetors this can be a gigantic challenge to today's modern tech lovers.

[@keith6872]

If your accelerater pump and carb are working correctly, but rich. The rich condition is fouling plugs slightly. Go to a hotter plug to fix stumble.

[@BigBlock-wf3mh]

Thank-you UT, good info, love the old school stuff …. Cheers! 🛠️

[@johnherdener6801]

Thunderhead 289 has a couple videos on carb and distributor tuning that can really help.

[@apocolypse11]

He actually makes the best videos about that but he's new school...odd

[@jacklinks6097]

Was dealing with a bog off idle in an old RV a few years ago. Changed the screen in the inlet of the carb and it fixed it.

[@chuckymurlo5654]

My 66 Dodge Dart had a bad stumble in sub-zero temps. So I fabricated an exhaust manifold shroud then connected it to the air cleaner with a flex tube. It fit perfectly into the snout just by chance!

[@kyferez1]

Great info! The only thing I think you didn't cover is which way is advanced vs the opposite which I figure I can't say due to silly filtering.

[@michaelramzi1094]

Master of carburator cars.

[@The_R-n-I_Guy]

I haven't had a carbureted engine in decades. But hopefully soon I'll get back to basics. I'll definitely need this information

[@edmundgutierrez1308]

This video described exactly what I'm experiencing with my 85 Jeep Grand Wagoneer. It stumbles at take off and then under load it's knocking. Factory spec calls for 19 degrees BTC and the brackets happen to block clear vision to actually set the timing accurately. I will be trying the power setting as you described today and I'm looking forward to it! Thank you!!

[@MrJosephfunk]

I read David Vizards book and he stated at idle the vacuum lowers the boiling point of fuel allowing the mixture to vaporize. When the vacuum falls due to opening the throttle the fuel reverts back towards being a liquid. The accelerator pump compensates the lean condition due to the transfer of the state of the fuel.

[@Oxmix66]

Another good video. Watching your videos brings back memories of problems I encountered years ago as well as what I found was the solution to those problems.

[@damienballard5]

Uncle Tony giving me the confidence I need to tackle my first classic car project. Wish I knew some of this stuff years ago. Thanks TONY!

[@Chevyv8man1]

Hey Tony, I totally agree with you on dial back timing lights. I have a Craftsman timing light from the 80s that I've had for years that I bought, that is the dial back style and I found it not being accurate at all so I took it apart and bypassed (removed the pot/dial). After that it works perfect and still does today. You just can't beat the old tools as long as you know how to use them. Later

[@blackforestmusclecars]

Simply thanks Tony for videos like that!

[@scatpack68]

I was able to cure an off idle stumble with an Edelbrock AVS2 by simply replacing the stock discharge nozzles with one from a late '60's Carter AVS. The stock Edelbrock nozzles are necked down and didn't allow for the needed fuel shot.

[@AZdadventures]

Thanks for the video. I’m trying to learn as much as I can. I wish there was someone like you nearby me I would love to get my Jeep back on the road.

[@thejeepdoctor]

Don’t forget about a weak EGR valve. If spring is weak, valve will just pop open and cause a lean mixture. Just unplug EGR and test drive vehicle. If it goes away, just leave it unplugged or replace it.

[@oldsrktracer]

Timing curve , fuel curve . Wether it's analog or EFI it has to work properly. Your timing has to move as fast as the fuel curve. I learned the hard way but it's the best way to learn.

[@michelmoss7559]

Wow, been so long I almost forgot I knew this stuff!

[@3Repete]

I don't have any stumble, bog or any other troubles. But tuning has always interested me, so you got a view. You just reminded me that I haven't really finished the setup on the Edelbrock AVS2 that came on my SBC. Might be able to do some timed runs and get the jetting right. Once it's there I can see how it does using your power timing move. I have always just gone 34 to 36 degrees all-in on my 350's cause it's safe and works. I suppose I should be trying to get all the juice out of my car. Otherwise I'm leaving power (fun) on the table.

[@jmetalsmith1362]

One of my favorite sources of info for chevrolet cars was the book put out by the factory on performance upgrades and tuning for chev 4 cylinder and V8s.

[@Hillbillygarage1215]

Thank you Uncle Tony, I have been waiting for you to post some hands on wisdom I can learn from. I'm sorry, I just don't enjoy the "chat" sessions.

[@Renegammradt]

Hey Toni. It‘s always good to have a look at your clips. Would like t thank you that. So I’m a slant driver from Germany. Keep on doing that clips.👍🏻

[@EarlwithanE]

Uncle Tony…today’s shop teacher…Awesome & informative video UT, Thanks!!!

[@timothybyrom5560]

Tony. The GM rigs pull timing with vacuum. When the vacuum drops they advance.

[@SchoolforHackers]

Is that manifold vacuum?

[@timothybyrom5560]

@SchoolforHackers Yes.

[@lawrence_tenn]

Great Info. I'm getting ready to start a new (to me) engine. I'll be watching multiple times to get the timing and Carb set.

[@bobbyz1964]

The problem I see with setting initial timing by vacuum or by ear is it doesn't take total timing into account. Distributor mechanical advance amount are all over the place with OEM distributors. Most times you'll find 15 degrees or so runs really nice at idle. If that distributor was set up originally for a couple degrees advance, it'll be way over once the rpms come up. If the original spec was 2.5 degrees ATDC like my 68 D200's 318 it's WAY over. Jump to my 81 W250 with a 318 auto the fender tag says 15 BTDC factory spec. Same basic engines, vastly different amounts of built in mechanical advance! So I never recommend those methods unless you check the all in mechanical. Best bet, find the initial and all in it wants, mod the distributor to match.

[@Joetechlincolns]

Wasn't 35 degrees total timing advance the rule of thumb for stock engines?

[@bobbyz1964]

@Joetechlincolns Somewhere around 35ish, but that's not carved in stone! Bore size, compression, combustion chamber design, fuel octane all play into it, plus, whether its naturally aspirated or force fed.

[@apocolypse11]

That's why efi is so good it made timing computer control but people only mention the fuel delivery of efi. Noobs

[@Frank-mt4qf]

Love your vids Tony I am learning hot rod knowledge from you keep up the great work thanks bro

[@musicauthority674]

I experienced this with a slightly modified 360ci FE engine. and fought it for quite some time. the engine was bored .030 over stock with a 539 lift 280° duration camshaft. with four barrel intake manifold and carburetor. I tried multiple carburetors and distributors but still had a lean condition issue. where it would cough up though the carburetor. and on Fords ported vacuum is used with automatic transmissios. and manifold vacuum is used on manual transmissios. and this vehicle had a manual transmission. I finally found that it was because I had a speadbore carburetor. using an adapter on a straight bore manifold. and the back cylinders would lean out because the primary throttle plates couldn't feed the rear most cylinders. because of the straight bore manifold.

[@robertbeckler5058]

Well UTG talked me into getting a g body. Said if he wasn't Mopar guy that's all he'd have. Just bought 83 olds toronado. Has a carb and a thousand vacuum lines. Guessing I will be watching lots of his videos know.

[@greenbassboosts8872]

Good news! Once you get it running right, all those vacuum lines will be in your trash can

[@davidbisnette7673]

Great explanation, Thanks

[@adamrosen7937]

#1 Best Channel on KZbin

[@outlawbillionairez9780]

On Ford pushrod engine, I attach a piece of stiff wire,bent to dist side,near the Dist. Mark dist with white marker. Make fine adj roadside by moving dist.

[@mexicanspec]

I am sure this video helped a lot of people, Tony.

[@RandallSoong-pp7ih]

Terrific! Thanks Unko!!

[@hunnybunnysheavymetalmusic6542]

Bad points gap can really mess up the spark timing, I have learned the hard way. A small amount of point gap error can cause the spark to come far too early, or far too late, and really mess up your timing!

[@bryancondrey6457]

The timing situation assumes your distributor gear and cam gear are in good shape and limited backlash. Older cars really need that examined and fixed as needed.

[@kevinclancy.]

great stuff thanks. when you are setting up TDC and adjusting by hand, remove your spark plugs so that you are not fighting compression (especially turning reverse when using the damper bolt),

[@61rampy65]

I had a customer with a 78 Monte Carlo w/ 305 V8. Complaint was a major lack of power. It would have good throttle response, but then it barely had any power at all. It had all the symptoms of a plugged cat converter. After replacing the cat and not solving any problems I discovered that the centrifugal advance was totally stuck. Removing the distributor and freeing up the weights made it run like new! Why did it still have some pep off the line? The *ported* vacuum advance gave just enough timing to take off, but as you opened the throttle more, that vacuum dropped off, and timing was back to where it was at idle. I learned quite a bit about timing after that! BTW, I have always used the "advance til it pings and then back it off" method, with rarely any problems. Glad I didn't try that on the Monte!

[@danrowley7002]

I used to find seized up centrifugal advance weights and stuck power valves in carbs on old cars as well. They both have to move freely.

[@combustion-junkiecustomart8083]

FANTASTIC video, thanks!

[@midsouth2strokes185]

Gonna work on the 78 Z28 tomorrow. See if i can get this stumble gone

[@sjcottsi]

You forgot the off-idle circuit. Off -idle slots transition the carb from idle to main metering. Some early 70s two barrel GM carbs had a screw in the back of the carb under a plug that you were not supposed to remove. They were often set too lean and would cause an off-idle stumble before the accelerator pump had a chance to work. They were called “off-idle air screws” so turning them in richened the off-idle mixture.

[@nedsmith3659]

This worked for me -- on a boat 351W -A vacuum gauge reading of 20 in. Hg Edelbrock 1409 Carburetor Step-Up Springs--stock was orange springs with bog than changed to the silver springs=8" bog gone

[@tedslife7086]

When I switched out my edlebrock 800 avs 2 carb to a Holley XP 750 I also needed more advance timing

[@justinschmidt9180]

I had a problem with an edelbrock carb that was new . It had a bog I did everything to it. It turned out the thermostat temp was way to low no fuel atomization

[@rooster68able]

(Zero lash )in-between the accelerator pump screw & arm

[@wilsondriver654]

What’s your opinion on setting timing on a ported setup, then switching to manifold vacuum? It seems to help start easily and then have lots of timing down low without too much up top. Like a recurve kinda, with better starting possibly. I’m running that on my L20b for now.

[@karlbischoff5181]

Great explanation, thanks Tony

[@golden.lights.twinkle2329]

Very useful. Now I have to figure out what type of carb and vacuum system my Fiat 600 has.

[@1Coolbanana]

Would love you to cover locking out distributors and timing on big cams, ignition and carb tuning. Ive onluy got 5" vacuum at best idling and even a 25 power valve is borederline. Im current running a locked out dizzy set at 40 degrees. That seems to be where it want to be from idle to top end, ut just works great, Any more and it starts to detonate and any less it wont idle!

[@danebeck7900]

How much risk is involved with the spark knock technique regarding potential engine damage?

[@peterrivney552]

Fantastic video Tony I've been out of the Hi Performance era for a few years now but im going back into time looking for a '70's unit Ford F-250 Highboy and want to trick itboutva bit nice stick grind camshaft intake manifold headers nice porting & polishing etc. The last toy I had was a '66 Olds 425 CI done up Punch 40 over 11:1 compression ratio heads done balanced aline honed squared block cross drill oil gallerys oil restriction on the camshaft oik relief slots cut into the rods 5-quart Toronado oil pan high volume oil pump and 9/16" pickup over 500 HP has tge camshaft advanced 4° then total timing at 32° change the weights in the distributor and just eliminated the vacuum advanced system all together '67 400 Turbo short shaft and used the switch pitch converter from a small block '67 2-speed Olds converter that was a switch pitch as well but a 2" smaller my high stall was 3800 RPM & low stall was 2800 RPM had a toggle switch on the shifter just above the trans brake and line lock had the 12 Bolt Posi clutches shimed solid and running 4:56:1 gears talk about dance took it out one on the street went to the speed shop yo grab a couple things left the shop in first easy hammered the throddle shifting into second car broke loose went sideways had to do corrective steering must have left a easy 12' of rubber on the road couple days later I met up with couple guy's I know and they asked if i was jamming on the breaks but they realized that i was letting it go ... I still wish i kept the carit was a '79 Olds Delta 88 Holiday Coup 2-door shouldn't have sold it a lot of time went into it expressly making up the jig to change the mounting brackets to fit the rear end into place and the upper links custom made.. it pulled the front wheels of the ground just mostly old school work six cylinder springs in the front have to admit they were fun times running it at the track at Dragway Park Cayuga Ontario Canada 11:30's. @ 112 MPH The camshaft was custom ground 328 / 328 duration 1/2 lift factory W-30 grind but being a 1966 - 425 odd bank angle of 45° all the rest of Olds motor's are 39° bank angle... Keep up the fantastic work Tony your one of my favorite channels slong with David Visser..

[@jonoh4883]

Muscle Car Solutions also has excellent deep dive videos on carbs and timing as well... great stuff..

[@marksmusiclive]

Great overview! Thannk you.

[@brianmilliard6998]

lol, I wish I knew more bout engine tuning, more specifically timing in the 80’s driving old $200 dollar beaters. We would never dare stray from the factory recommended settings.

[@gerdberg4188]

When you started talking about this I thought …wellll …hmmmm. ….accelerator pump has to be one of them ! Yay I guessed it ! I have had slant sixes all my life . I have two 66 darts. And 82 miser

[@fredsolomon3rd6969]

Nice break down, how it will works.