Carburetors and Gas Mileage: 5 Things you need to know!!!

[@adamrodenberg1557]

I just thought I'd mention a cool little trick I learned. If you're having a hard time keeping your idle/throttle stop and mixture screws in the range that they need to be in, you can change your PCV valve size to increase or decrease the idle air flow. Lots of folks will tell you to drill holes in your throttle blades to do the same thing, but it's much easier to change a PCV valve which acts like a calibrated vacuum leak.... Great videos keep them coming!!!!

[@lollipop84858]

Ok, so are you going to give us any more info..? Change it from what to what? Bigger? Smaller? Bigger than what baseline? Smaller than what baseline? How do you check them to know what you have and what you're getting?

[@here_to_watch2115]

Ive womdered aboit this. I jabe a 91 c1500 , the pcv sucks super hard so i realized recently it may need bigger sized pcv in it. Inwondered how it would effect idle.

[@UnfinishedProjectDartSport]

A vacuum gauge can help show you just how much your foot varies on the pedal, and just where to keep the throttle for maximum fuel mileage on your combination.

[@BuzzLOLOL]

His #4 - Gear ratios wasn't why 1970's cars got horrid MPG, it was emissions slug engines with actual compression ratios in 7's (always claimed as 8's), but still using mismatched 1960's cam grinds, retarded camshaft and ignition timing, EGR valves, A.I.R. pumps, and rich carb. jetting all working through early restrictive catalytic converters/single exhaust...

[@BareRoseGarage]

All 5 are Spot On Man! and I'd have to say that number 5 is the biggest one in all of it. I had a 2001 Dodge Cummins 4wd HD 3/4 ton truck with the 6 speed close ratio manual. When I drove it, it would pull 26-27 mpg all the time even loaded down hauling double trailers full of shop tools over multiple Rocky Mountain High Passes (moving a friend from Idaho to Utah). But when people would borrow that truck, they complained that it was a Fuel Hog POS. It all came down to driving style. I drive by the Tach not the Speedo. I shift by the Tach (well I hear and feel it because I'm used to it). I kept that Cummins in its happy place at around 2,000 rpm and let it do the work it wanted to do... and everything was happy happy happy. Speed Limits on our Interstates are 80mph.... but it's legal to do 65mph in the right lane and enjoy the ride as she sipped the fuel all the way to where I wanted to go. The friend that I was helping to move, he had a Ford Powerstroke and did 80 all the way there. We got there at the same time because he had to stop for fuel twice.

[@jasonhooey5677]

You are correct sir! Read the road traffic, don't speed, easy on the right pedal and just cruise

[@treyrags]

Good points made. I would put ignition timing #1. If its not right carb tuning will make little or no difference. My 600 HP 438W gets 14 mpg with a 1050 dommy. I do have vacuum advance, Gear Vendors overdrive, and the help of O2 and map sensors. Plugs are clean and dry, tailpipes dark gray. It does take lots of testing at various loads/rpm to really zero in on it but its worth it. A side benefit of lean/advanced tuning is a cooler running engine and cleaner oil 😉.

[@jeffrey4547]

u are getting 14 i wish if i baby my rig i get 8 mpg if i stomp on it u can watch the gauge drop

[@logician7517]

What CR are you running and what are the specs on your ignition curve (initial and total advance)?

[@treyrags]

@@logician7517 10.9:1. 21 initial, 33 total at wot. 45 total at cruise w/vacuum advance

[@Texasmule]

1050 dommy mommy?

[@guamazolopez6456]

how do i make my engine high compression like a 5.3 truck engine

[@briansd2772]

You're not crazy Andy. You're practical with a little fun mixed in. Love your business model. Thank you!

[@bcbloc02]

The solution is you need more gears. The slower you can revolve your engine and still make enough power to pull the vehicle the better the fuel mileage will be. This is the reason most vehicles today have 7-10speed automatics. It allows those deep reduction gears for quick acceleration while having those very low numeric finals to knock out outstanding MPG.

[@UnityMotorSportsGarage]

That's exactly right.. cars today have best of both worlds! Thanks for watching brother Andy

[@yepitsme431]

Another thing is that with those multispeed trannys the engine is almost always kept in the most efficient RPM range wich make a huge difference with speed/aceleration and gas mileage =)

[@BuzzLOLOL]

@@UnityMotorSportsGarage - Your #4 - Gear ratios wasn't why 1970's cars got horrid MPG, it was emissions slug engines with actual compression ratios in 7's (always claimed as 8's), but still using mismatched 1960's cam grinds, retarded camshaft and ignition timing, EGR valves, A.I.R. pumps, and rich carb. jetting all working through early restrictive catalytic converters/single exhaust...

[@fastinradfordable]

Outstanding MPG means 50mpg avg at least.

[@BuzzLOLOL]

@@fastinradfordable - What is outstanding MPG depends on the size, shape, and weight of the vehicle involved..

[@joe-hp4nk]

Higher compression means higher octane fuel that's more expensive which cancels out the better mileage.

[@santacruz59]

This is a video about fuel economy not gas prices….

[@joe-hp4nk]

@@santacruz59 Duh

[@santacruz59]

@@joe-hp4nk Exactly. Gas prices have nothing to do with fuel economy…..your comment makes no sense

[@joe-hp4nk]

@@santacruz59 Higher gas prices cancels out fuel economy, it's all about the bottom line.

[@rotaxtwin]

Great stuff, scratching the surface as you say but I agree w all of it. You were able to get 16 mpg w your old combo because you understood how to maximize efficiency through your spark curve as well as the many carb bleeds. Your new distributor setup is the cat's ass of efficiency tuning. It kills me to see a hot rodded car running no vacuum advance. I also believe a lot of the horrid tune of the malaise Era cars worked only on the EPA test cycle and nowhere else. Gawd those were dark times.

[@davidvander2233]

Vac advance interferes with the lopey idle misfiring that some people adore

[@UnityMotorSportsGarage]

You just need a bigger cam ..lol jk

[@josephverdone7099]

Like your videos. I have a 409 sbc sprintcar engine which Sammy Swindell engine builder built in 1995 a 400 4.165 bore 13.5 , Brodix Heads ported a monster w/ Progression ignition & a Carb Cheater running 110 octane I run on the street built for the road course. Carb Cheater and Progression work great together.

[@hoost3056]

If you want max driveline efficiency, you want a direct drive style transmission with no overdrive. Truck builders figured out that frictional losses in overdrive cost mpg.

[@uncle_moose]

Manual gearbox😉

[@deanstevenson6527]

Truck rules are great. You can find wrecking yard mid and late 70s gearboxes, like the Porsche 928 style 1:1 ratio top gear 265 Getrag 5 speed from a BMW 528i or Volvo 265, an overbuilt gearbox which works great on a Fox Body, where you can still get 2.47 ratio 8.8" gears from an F150 4.9 liter Six. Ratio spread from top to first can can be wide if the engine rev range is narrow, another truck rule. On lightweight cars with a wide rev range ( 67-71 Z28's with Fuelie heads, or Big Block Muscle cars) an M22, A833 or Top Loader doesn't need 5 gears, but with a 1:1 top, it will work real fine with 2.46 first gear and a set of 3.36/3.23/3.25 gears. Modern cam tech and better breathing intakes and great carbs don't require 3.90 to 4.30 gears and a lopeing Gearvendors overdrive anymore.

[@ronnieb7408]

If this was totally true then why do semis have overdrive and many have two overdrive gears,besides the fact they get 7mpg and more with 80000 pounds gross weight. Empty is between 10 to 15mpg at 30000lbs

[@hoost3056]

@@ronnieb7408 once again, because of frictional losses. The driveline you described is old school. "Yeah, my Pete 379 gotta a Cat, a 13 with a single over, 3.55s on tall rubber." But the engineers learn and now it's "I got a DD15, a DT12 direct 12 speed and 2.29s on low profile 22s." The ratio spread may be the same as the old school but with less friction.

[@ronnieb7408]

@@hoost3056 Not old school here ,I drive an X15 cummins ,10 spd eaton with overdrive that gets 7.5to 8mpg average with all types of loads and an aerodynamic truck at that. 75mph governed. Ive drove about everything there is and know my stuff as well as Vizard when it comes to autos/diesels

[@65sohc]

In the early 70's a well-known engine builder/racer named Ak Miller did a lot of investigation into mileage. His theory was pretty much the opposite with respect to throttle opening. He reasoned that the greater the throttle opening for a given speed the lower the pumping losses through the engine. One of the reasons, it has been said, that diesels are inherently more efficient that gasoline engines is because they do not have throttles so the pistons are not sucking against throttle blades creating manifold vacuum. What was found to be the most important factor in fuel economy was engine speed. Therefore Ak had full size Fords and Mercury's with rear ends on the order of 2.20:1. Fuel economy was excellent but acceleration was terrible. Fast forward 50 years and now every vehicle has an overdrive transmission. The effect of engine rpm on fuel mileage is dramatic and easily demonstrated. My C8 Corvette has a 5.17:1 rear end. 8th gear is 0.33. If I set the cruise control to 70 mph I can monitor the fuel mileage in each successive gear. 70 mph in 5th gear is about 2800 rpm. MPG is around 17. Shift into 8th, rpm drops to about 1350 and mileage shoots up to 29. I don't know what the relative manifold vacuum readings are in those two scenarios but almost certainly it is less in 8th. Mileage is much better due to less frictional losses and to a lesser extent less pumping losses. The rule of thumb is for maximum economy run at the lowest possible engine speed.

[@josephverdone7099]

I agree on the gear size but also keep in mind the difference in wheel/tire size.

[@here_to_watch2115]

The throttle opening amount is one reason a question jet is so awesome. 2 baby barrels to drive on and 2 monsters for the wot.

[@gregleenyit]

Thanks Andy I have always been a big proponent of the tighter the squeeze the bigger the bang. I can't remember your old 393 if it had iron heads? I feel 11to1 with aluminum heads is a bit on the conservative side especially with 93 octane we have on the East coast. That distributor is Slick! I think everything you said was Spot on! Excellent video again. Now go get UTG money😉

[@kurtzimmerman1637]

good video Andy! I always said compression is free power. take care.

[@UnityMotorSportsGarage]

Thanks Kurt, you are right Andy

[@frontporchsittinwithdoobie7990]

Vacuum gage on dashboard would help with driving habit in my opinion Most new car have something similar

[@UnityMotorSportsGarage]

You are exactly right.. it will open your eyes as to what is going inside the engine Thanks for watching Andy

[@tsufordman]

Some older GM cars had them. I think they were called efficiency gauges. But the needle worked reversed to a vacuum gauge.

[@shoominati23]

I had a Datsun 120Y with one of those, if you tried to keep it in the green you would drive so slow off the lights you would get the cars behind beeping at you and barrelling past to overtake lol.. In my opinion they are for larger engines in heavier cars, not a little 1200 in a 900kg toybox ;)

[@mikesperling8758]

Hey brother I love all your videos they're almost as good as dv besides he's got you on about 50 years of crazy knowledge that nobody else talks about keep putting them out love them all

[@mitchcoop1]

Sorta close but....way..way..over simplified...octane...manifold distribution...air inlet temp. & about 20 more things...Good luck.

[@brianalbrecht4423]

Exclent video Andy...spot on...!...look'n forward to see'n Casper suck'n huge amounts of air & fuel @ the no name nationals...get back to work...thanks for u & D.V. taken the time to make this video...good luck @ the n.n.n....reguards Brian

[@UnityMotorSportsGarage]

Thanks Brian! We are looking forward to the NNN! Andy

[@dennislaws5187]

68 years old, been a mechanic much of my life, Started with learning to rebuild the 427 sideoiler iin my 68 Shelby GT 500 and when i was 18 in 1972. i also worked at 3 Ford dealerships as a line mechanic, and I learned a lot today Andy, I also live in NC very northern most point of Rutherford county, on hwy 226.

[@UnityMotorSportsGarage]

Thanks Dennis! I've been on 226 many times in my life up near you

[@dennislaws5187]

@@UnityMotorSportsGarage Golden Valley

[@dennislaws5187]

@@UnityMotorSportsGarage Which route did you take to tennessee, 77 to 40 or 74 to 26?

[@UnityMotorSportsGarage]

@@dennislaws5187 321 to 40

[@dennislaws5187]

@@UnityMotorSportsGarage wow, I lived for a time in High Shoals and used 321 to 40 often and forgot about it.

[@paintnamer6403]

When I was changing jets for fuel efficiency in my Holley 750 DP I did get to the point of part throttle surge and when I switched back to the factory duel snorkel air cleaner it would ping.I did get it to run great, just some of the things I experienced in my day. The factory Thermo Quad with the strip kit ran the best ET wise. No bad against Holley, that 440 wanted more than 750 cfm. The stock Holley was 570 cfm on my '69 350 horsepower 440.

[@shoominati23]

Get one of those K&N 14 x 3" air cleaners with the filter material on top aswell

[@paintnamer6403]

@@shoominati23 This was 1988 and I did use a 14 x 3" open element air cleaner and that worked well. A side note, there were so many people telling me I needed a new air filter because how the K&N looked dirty! They were so used to seeing paper element filters.

[@MrWill73]

Andy, you are my carburetor guru!!! Great video! Great tips!👍👍👍👍👍

[@miker7294]

Lots of great pointers. Keep the videos coming.

[@95Sn95]

Low axl ratio and a tall OD final gear is the ticket. I have a 350hpish SBC in my pickup I had Howard's 112031-08 cam Torker 1 and modified 800 q-jet and it got about 8mpg, the q-jet did not like the combo at all, I to tossed a 600 Eddy on it and my milage jumped to about 15mpg+ so having a carb that made power but didn't work optimal was cutting my fuel economy in half...!

[@ericsmcmahan]

Andy, u r a tuning genius!

[@UnityMotorSportsGarage]

Eric thanks for the kind words..but that isn't really true.. it's one of those things...the more you do it the better you get! You learn what works and what doesn't over time... That's sums it up. just a average guy who likes to learn Thanks for watching Andy

[@ericsmcmahan]

@@UnityMotorSportsGarage if those hammerheads and rocker arms prove out for you on reliability, I would like to try a set of them on an ls engine. If I buy a comparable set of those heads somewhere else, it will cost me over $15000 for head and intake package. I am hoping these could save me a little money. I know that I will have to build an intake. I was told that I can modify and use an sb 2.2 intake. I will keep on following the project mixed up boss. Keep up the good work.

[@UnityMotorSportsGarage]

@@ericsmcmahan I feel really confident in them, Greg Brown working Jesel put a ton of time and effort into the valve train making sure the geometry was spot on. That would be pretty awesome to see a LS built with them! Go for it Andy

[@hotrodray6802]

Geez. All these guys bragging about their highway mileage. How much time do you spend on the concrete interstate on level ground with zero headwind? 2%, 6% ? LOL. You'll use less gas if you leave it parked.

[@RabeHighPerformance]

My dad's old 1965 Buick 225 Electra 4 door sedan with 425 cubic inch nailhead v8 with 10: 1 compression ratio. On the highway it get 22 mpg in the city it get 18 mpg. That's from 4800 lbs land yahat. That with a 3 speed automatic transmission and 3:42 rear gears.

[@hotrodray6802]

LOL. 15 was reality. My uncle had a new one.

[@johnstuchlik5828]

My 65 LeSabre w 300 cu original afb ,3sauto ,.3.25 only got 15.hwy.

[@sheldonbromen2603]

People look at me funny when I tell them I'm getting 27mpg in my 351w sn95 I baby it and just cruise in it t5 with 2.73 gears and at 65 its at 1300rpm almost just idling

[@johndevries8759]

Looking forward to the next video where it all comes together. Thanks

[@cutl00senc]

What he didn’t mention, but applies to any gasoline ICE, is idle time. People sit in parking lots with the a/c on in the heat and idle their engines for 20-30 minutes…..and then complain about the price of gas. Never mind the fact that idling an engine is about the worst thing you can do to it.

[@95Sn95]

It would be so awesome to have access to Dave's knowledge.... That guy has so much knowledge of air flow from being OCD when I comes to understanding something and getting that last efficient cfm maximizing a components full potential. When he takes a total turd of a head like the e7 and making it flow like a champ that's impressive.I can't imagine anyone knowing more

[@UnityMotorSportsGarage]

DV is brilliant... I have seen him do some crazy things... Like getting 275cfm from a pair of E7 heads! In nearly 20 years he has taught me so much.. Thanks for watching Andy

[@markcordial4938]

Could not agree more with you guys on DV. David vizard = the truth the whole truth and nothing but the truth with regards to the thermo dynamic mechanical pump as he puts it the man's an engineering legend.

[@brianb5779]

Andy if i was you I would be recording all these conversations w Vizard. Whether it be for your own personal library or to share w others. When that man is gone (GOD forbid) all these discussions will be a treasure to you and others.

[@lollipop84858]

Why? The man has written several several books, and has his own channel he immortalizes himself in

[@347mav3]

Years ago I put together a Holley carb for e95 to run on my 347 in my Maverick. With some tuning and patience I got 15mpg with a 4.10 gear and an 11-1. 347

[@UnityMotorSportsGarage]

That's even more impressive with E85! Thanks for watching Andy

[@reason2gether]

Well said Andy. Near the end where you mentioned the Dominator carb having larger throttle plates allowing a more closed-throttle setting at idle; the same thing is achieved with the 4150 carb by drilling a small hole in the primary throttle plates to allow the same required airflow for the big engine's idle requirement while keeping the throttle closed as much as possible. This allows for true idle circuit tuning to be done without the detrimental effects of exposing the transfer slot as you mentioned. Great job addressing the issue of how mpg is not exclusive to non-performance engines. Most aspects of performance tuning are for best efficiency and go hand in hand with mpg as well. God Bless you Andy and Mr. Vizard as well.

[@WrenchingWrecked]

I've been testing this same theory as your drive train portion. I have 2 302 powered vehicles right now, 73 Ford Econoline (built out camper style, really heavy) and a 64 F100 with 3 on the tree to floor conversion. I swapped roller cam motors in both, but with the truck 3.25 rear end and three speed, I'm pulling 17-19 in. of vacuum at 70 (about 3k rpm), and need very little throttle to maintain. I swapped an AOD into the van, with 3.89 gears and will be at 1900-2000 rpm at 70. However, in OD at 70 vacuum drops down to about 10-12 in. at best. I've been trying to monitor and assess which yields better MPGs, higher revs less higher vacuum, or lower revs. Obviously both vehicles are quite different despite similar motor setups, but I can get about 17-20MPG on the truck if I keep my foot out with the current gearing (also has AFR heads and a 500cfm carb), where the van has forever been stuck in the 10-13 range. My next move is throw an AFR gauge in to analyze further and post results on both combinations. THANKS for sharing!

[@BuzzLOLOL]

Compare van MPG between 3rd and 4th gears... also tire diameters for van and truck... was van motor a weak 1970's emissions slug engine?

[@WrenchingWrecked]

@@BuzzLOLOL Both van and truck have roller cam 5.0 motors fresh rebuild on both. Vans only got about 300 miles since rebuild. Van has bigger tires than the truck and significantly more weight due to the camper buildout in the rear. If cruising at 70 4th is fine unless I hit a hill or incline. 4th OD wants to lug elsewhere and I usually leave it in 3rd until about 60+ now. I may actually try a set of 4.11 to help pull the weight and stay in a more efficient power band.

[@BuzzLOLOL]

@@WrenchingWrecked - Wouldn't change rear gears, just downshift to 3rd as needed... Ford started roller cams about '84 as I recall... GT40+ heads are more efficient than the earlier heads... roller cams used with both head styles...

[@travispfannmuller7717]

in my experience heavy vehicles like your van are a lot happier with more cubes, my experience is with gm but i tugged the 305 out of my square body 4x4 blazer and put a 454 with a torque biased cam and gained significant drivability and fuel economy. higher compression would have been beneficial but it was a stock 454ss long block which are born with dismal compression ratios (high 7's)

[@unclesquirrel6951]

Personally I blame squirrels

[@UnityMotorSportsGarage]

Me too..

[@shoominati23]

WHy don't you be his (Dave's) new assistant now poor Marvin has passed on?

[@DonaldSanetrik-cl3lt]

Higher tension throttle springs help with learning throttle control

[@asbelfernandez3598]

Something I would add to this information given , I recently reinstalled my crankcase evacuation system with the one-way check valves repositioned 2 in. from the breathers on the valve coves because they kept blowing out when I had them right on the header collector I'm going to see if moving them away will make them last longer and after I connected them and drove on the highway the motor had picked up 3 in of vacuum on the cruise the the cam is on a 106 lobe center angle with what many people tell me is ridiculous duration at 50 I don't know exactly how many miles to the gallon it gets but I've driven the car 3 hours at a time without sucking the tank dry also fuel ratio leaned out with the crank evac. Wear it highway cruises in the upper 14s and upper 15s at 388 cubes 411 gears pump gas flat lifter car runs in the tens.

[@davidvander2233]

EFIs main mpg advantage is under decel when the injectors shut off

[@UnityMotorSportsGarage]

That's exactly right...

[@threadtapwhisperer5136]

I think the EPA is full of shit and fuel injection is only used to capacity by aftermarket tuners. I beleive that the original organized leak(IE carburetors) when kept properly tuned and regularly maintained are just about same-same when compared to Fuel Injection. I feel the other functions of a PCM controlled engine/drivetrain like millisecond control over timing changes and saving a bit of fuel when cruising.. Maybe. Carbs always were working on the concept of veturi's and airflow over a orifice through the annular dealies. Also, that 1978 or so 454 the corvette had showed just how shitty the original concepts of achieving fuel mileage were. 454 cubic inches and mamma jammin 160hp. How. The. Funk. Crappy flowing heads and a dead ass cam with a mildly moist fart of compression, turns out that doesn't actually make performance nor does it make any actual fuel economy. Dang ol thing cant make the powet to move its 454 buns along efficiently. But im no engineer, just aint down to outright trust any corporation implicitly just because they claim some BS.

[@budlanctot3060]

There is absolutely NO QUESTION in my mind that computer controlled FI is superior to carbs in cold weather operation and reducing fuel dilution of oil. This contributes to modern engines lasting twice as long before bore/ring & brg wear requires engine mechanical intervention. With FI the oil stays cleaner and lasts longer. I agree that after warm-up, once cruise is attained a properly tuned carb can be just as efficient. But the choke/engine warm-up is the fly-in-the-ointment for carbs.

[@bobmopar2587]

Great video Andy.

[@forestlawrencegrading9154]

Andy your kind of crazy is a good thing I am sort of interested in edelbrock's New version of the 4150 I hope you and David get your hands on a couple of them I would be interested in what you too would have to say about them⛽️🇺🇸

[@UnityMotorSportsGarage]

I love those new Edelbrocks based off of what I have seen! I would love to get my hands on a pair of them to see what all can be done with them Andy

[@hoost3056]

The other thing to do is use the best lubricants available. Look up WPC Treatment....it reduces friction substantially. Most of the driveline friction is in the rearend. Getting all the rear pieces WPC treated can free up some mpg.

[@joe-hp4nk]

Manifold vacuum at idle connected to the distributor gives you full advance. When you go part throttle the vacuum drops off and you lose advance when you need it the most. You must connect the distributor to the ported port where there's no vacuum, then you get advance at part throttle when you need it the most.

[@treyrags]

That totally depends on the engine combination and. Compression, cam overlap, initial timing, etc. My engine actually climbs vacuum immediately upon cracking the throttle with manifold vacuum. It only drops when the throttle gets significantly opened under a heavy load or acceleration where the squirters fill that void

[@reason2gether]

Manifold vacuum advance actually works better with the dynamics of a performance engine. At idle it gives the engine full vacuum advance which raises the idle efficiency so that a more closed throttle position can be achieved. When the throttle is opened, the vacuum dips in unison with the engine load increase. At this point, low rpm with increased engine load, the reduced ignition timing is desired to prevent "burst ping" or detonation. As the engine rpm increases under the opened throttle load, the centrifugal advance is taking care of the ignition timing requirement all the way to the full advance setting needed at W.O.T. which is usually 34-38 degrees of timing (this is achieved with the combined best ignition base-timing setting added to the full mechanical advance setting set by the tuner in the centrifugal advance mechanism). Once the acceleration is over and the throttle closes again, the manifold vacuum returns and supplies the needed extra timing to prevent idle misfire and stalling. Since the manifold vacuum "pivots" around the engine load (vacuum increases while load decreases, and vacuum decreases while load increases) it works in better unison with the actual engine requirements. A good tuner will know this and take advantage of it. The ported vacuum you are referencing is only good for light throttle settings where you are possibly looking to gain only a fuel mpg increase. In a carbureted performance vehicle, which is what most of us here are working with, mpg is secondary to performance. If you use ported vacuum with your carbureted vehicle, you are not seeking or getting the best performance to go along with it.

[@treyrags]

@@reason2gether agree with all except the generalization of the total timing. Every engine is different and I've seen chambers that are efficient enough to only want 26 degrees total for best WOT power.

[@reason2gether]

@@treyrags Yes, that is why I said "usually". I meant that once the best total timing is discovered for a particular application, that it is best achieved with the Base timing and Centrifugal timing together without the need of or interference from "Ported" vacuum in the mix. In my experience mostly with naturally aspirated SB Chevrolet engines, the best total timing at W.O.T. usually falls within the range I mentioned. You are correct that different combinations and designs may need higher or lower amounts of total timing. Finding and setting that timing is the job of the true performance tuner.

[@joe-hp4nk]

@@reason2gether For cruising I find ported vacuum works best on my 454. A all out race engine will have the distributor locked out at full advance.

[@scriptmike]

Emissions go up with mileage. Really co2 and nox go up with great mileage. Bad emissions like co and hydrocarbons are not present, because of the clean lean burn.

[@UnityMotorSportsGarage]

I have always thought that to be the ironic part.. Thanks for watching Andy

[@Channelscruf]

I am what is known in some circles as first.

[@robsdeviceunknown]

Gaining fuel mileage via compression can become counterproductive if you have to run 92 octane.

[@JayMalone26]

Not necessarily. My 1998 SL500 has 11.5 to 1 compression. Im very very surprised how little fuel it consumes.

[@treyrags]

I've been meaning to ask you how you are liking that Progressive system. I really am interested in it. As you pointed out, I think it will really help dial in your fuel efficiency with its it's timing curve adjustability

[@ronnieb7408]

I have two examples on fuel mileage..1st one 89F150 extended cab that weighs more than Casper, 302 , 0.67 overdrive,3.55gear, 29" tire that got 20mpg and had over 500000 miles .2nd example 92 Z71, 350 with 4bbl carb converted,5spd manual 0.80 overdrive,3.42 gear,33" tire got 16 to 18mpg if I kept my foot out of it. The Ford was EFI and the Chevrolet had TBI but got better with a 600cfm 1850 carb ,Edelbrock intake and HEI distributor.Both vehicles are the same weight or more than Casper and both are basically aerodynamically close (shaped like a brick)

[@b.s.adventures9421]

I had a 69 el Camino with a fairly hot, old school build, very well tuned 283, 4 speed, 3:36 gears, 26” tires. It would get 17-19 mpg at 65 on the freeway. Was also a pretty quick fun little car. Could beat a gen 4 SS Camaro, trans am, cobra mustang of the era, 5.0 fox, etc. in a street race.

[@600wheel]

#1 fuel injection is better😂

[@UnityMotorSportsGarage]

Lol.. Thanks for watching Phillip! Andy

[@Otani_Garage]

I really like how u mentioned that the final drive gear ratio can have a large effect on fuel consumption. I think that’s the reason why late model vehicles have transmissions with more speeds. Essentially you can have the best of both worlds if you have a taller final drive and simply have a shorter first gear (and second and third). Then you stick the transmission into overdrive or even double overdrive in some transmissions and you get that low cruising rpm you need for good highway fuel economy. Today’s “close ratio” transmissions are a lot wider in spread than close ratio transmissions of the 60s and 70s. Of course this is a simplification because modern engines have many ways of broadening their torque curve and usable powerband but I think this must be one of the main reasons for that change.

[@kentbarger8628]

I am a retired mechanic I had a 65 Ford Galaxie with the 289 V8 and a 2 barrel carburetor 4 speed on the floor and it was a four-door vehicle I pulled a 5 x 10 enclosed trailer I modified the carburetor for mileage going through Kansas and Missouri I got between 23 and 1/2 up to 24 miles to the gallon my grandfather was a head mechanic for Ford dealership taught me how to modify carburetor for mileage and high-performance the technician in this video is a very skilled technician I love working on those old cars it brings back a lot of good memories take care of you one and have a wonderful day.

[@libertyjusticeforall6754]

Thanks Andy , your a good man. Much appreciation for you sharing such high quality information, and tuning. I watch all your videos, usually more than once. Wish I was there to hang out and wrench with you . I Always Look forward to your videos daily. Much respect and love for u brother. Aloha all the way from Hawaii to you and your family. 🇺🇲🇺🇲🇺🇲🇺🇲👍👍👍👍💯

[@terrygrover6440]

Hi Andy i think your right about the gear people back in the day would have big boat big block cars with high compression with the timing retarded and run regular gas and tall tires with no gear and drive 40mph thinking they were getting better fuel mileage while actually lugging the engine and most of the time you'd see black smoke out of the exhaust and wondering why they are getting 12 miles to the gallon 😂😂

[@hoost3056]

I drive truck.......my Series 60 Detroit has 16.5 to 1 plus boost plus a high energy head plus a cam that makes peak torque at 1200 rpms. It can do 7 mpg at 75k pounds plus.

[@darrenkite8184]

Hi Andy , get video buddy .. have you checked out dambest carbys .. there in America.. look good too and look like they get better atomization of fuel too .. I know your a busy bloke .. just thought you might like to check out a KZbin video that he has done .. my thought would be better atomization would equal MORE power , MORE torque.. I’m just a little backyarder from Australia who started watching David Vizard , then started watching your channel too .. Andy & David show great information in these KZbin video .. I have nothing to gain from dambest carbys.. hope to hear from you and see what happens.. cheers

[@conniekahl8015]

How about a Blower carb set up? I've got 351M, FMX, 6/71, dual 600s with 427 progressive linkage, MSD 6AL using modded Ford dist.8 inch 4 link with 4.62 gear in a chopped 32 3 window coupe and 31inch tire. What do you think? Please!

[@randywl8925]

Many years ago during a mild rebuild of my Chevy 350, I pulled out Mr Mastercard and ordered a Holly 650 spreadbore. I loved the tiny primary's on my Qjet for mileage. I opted for the vacuum advance model not the infamous double pumper. This wasn't going to be a race truck. I had a month of frustration tuning this carb. I could gain a mile per gallon with a crappy idle, or tune a normal, smooth idle and lose a mile per gallon. It was then, that I discovered the stupid design of this carb. The idle screw adjusted the idle mixture and the transfer slot.. On this emissions carb both circuits drink from the same well. This carburetor was different as to richen the idle mixture you turn the screws in not out. The idle mixture screw is blunt not pointed. Worst purchase that I made while building this motor was that untunable 650 spread more from Holly. I was able to make it better by messing with the emulsion tube openings by drilling them out slightly and inserting bent pieces of fine wire to fine-tune the restrictions so yes I was able to make it run better but please if they still have that carburetor don't buy it. The keywords are emissions and reverse idle screw. You do not want that. Fantastic video by the way. You're so careful and precise in your wording that everything makes perfect sense. 👍

[@UnityMotorSportsGarage]

Randy, thanks for watching and for the kind words.. Those emission Holley's are the worst.. I have only messed with a few of them... I try my best to stay away from them! Andy

[@randywl8925]

@@UnityMotorSportsGarage I have a Holly book and it mentioned somewhere in the article about taking fine wires such as those from a standard wire brush to reduce the diameter and flow into the orifices or openings leading to the emulsion tubes........ The wires were cut short then bent into a v and pressed into the brass opening in the metering block. You could press one two or three of these tiny v-shaped wires into the hole and they would stay there. The diameter of the wire and a little math would tell you approximately how much volume they would reduce in the flow. I still have the carburetor but I don't have my Chevy 350 or the pickup. It's a real fight to work on emissions carburetors and I'd certainly never do it again but I learned a lot. Thanks for doing what you do for the old school automotive enthusiasts.

[@Redneckairflow]

I had a 91 Chevy 1500 with 3.42 gears a stock 350 (200hp and tbi) with a 700r4. At 55mph it would get 15 to 16 mpg but run at 65 to 70 it would get 17 to 18 mpg. Just by bring the rpms from I think 1500 to 2000 it wasn't lugging the engine and allowing it to be able move the truck around easier. No one believed me and yes this was figured on paper and had stock gears, tires and speedo calibration. Loved that underpowered truck.

[@car_ventures]

That makes sense actually, it probably had a 4l60e which may not have locked up until that higher rpm. Plus that higher rpm was more in the power band meaning it only needed light throttle movements to notice a change in speed

[@Redneckairflow]

@@car_ventures it had the 700r4 non electronic trans. I put a flow master muffler in place of the stock muffler and at 55 you could just hear the engine wasn't in it's sweet spot

[@johnelliott7375]

I think 🤔 you're going to be in the ball park with the theory and your hard work along with Mr. V., Is going to get you where you are going to need to be. Only thing is as you said you are going to have to dial it in as you always do. The "Crazy", part about it is that I believe that everyone who has felt that feel good WOT with that, we will say seat gluing G's that keeps the other occupant from reaching out and grabbing that 100 dollar bill 💵 from the dash board the best part of the work along with the rush of the fastest ET makes all the hard work so much worth the time and effort to enjoy that 6 seconds of life. Hopefully that makes sense to everyone for I never was great explaining my thoughts and adventures. Great day to you all! Thanks again and I will be sharing away as always! Too bad I never had one that would get to the other side in less than 11 seconds.

[@shvrdavid]

Great info Andy. Where this info will really shine, is with high compression street engines. And I am talking about 13 to 14+ to 1. I ran a BBC at 14.2 to 1 on pump gas on the street in the 80's (about 97-100 octane if I remember right), and it was perfectly happy going down the road at 15-16 to 1. The higher the compression, the leaner you can usually get away with it. The camshaft, centerline and dynamic compression has a lot to do with what you can get away with as well. That BBC had a marine solid roller with close to 700 lift, 270/290 duration @050. It had iron heads as well with coated chambers and pistons. And it did not need much timing at all to go down the road. The nitrous system used methanol and I had the timing set up for that all the time. That was the first engine I built to use pump gas with that much compression. It was in a back halved 69 Chevelle with 5:38 gears, and it wasn't light either. I know, why so much gear? It was only 408ci, 4.25 x 3.6, and yes it screamed. Most people assumed it was a small block to listen to it rev that high. It was originally set up for the 1/8th and the street. That engine also had oil sprayer bars so the rockers and springs would survive and oil bars for the rev kit. BBC's are hard on exhaust rockers and springs on the street, with cams like that it is just plain hard on everything.... Many of the ideas to build that engine came from David's books. But not all of them, lol.

[@318willrun]

yep, yep, and yep 😎

[@UnityMotorSportsGarage]

Im excited to see how the van turns out! good stuff.. Thanks for watching Andy

[@johnmartinii77]

A lot of good common sense thinking right there.

[@EYE_SPIDER]

12mpg isn't to bad - good video brotha!

[@UnityMotorSportsGarage]

Thanks!

[@johnelliott7375]

I have been waiting for this and you are getting closer to the end game on your Mixed-up Boss Finished product and we couldn't be happier for you and the completion of your truck! Good morning to you and I hope that you have a great day and a awesome weekend! Thanks for sharing your work and dedication about your tuning secrets with us all.

[@LeftForDeadGarage]

I managed over 15mpg with my junk on PowerTour. There may be more to be had since there wasn’t any time for MPG tuning. My driving style on the trip was extra Pawpaw so Iam sure that helped. I really didn’t want to have to make the “come get me” call that far from home.

[@UnityMotorSportsGarage]

I know that's right!

[@keithiverson6687]

Gearing has a lot of variables to optimize for mileage and fun. It has to match engine power delivery, weight, highway drag, tire size, transmission gearing. I had a 99 Cobra with 3.27 gears and a .62 overdrive, engine made peak torque at 4800rpm. I did a highway mileage test with it once on a 3hr one way drive. On the way out I drove in 4th and the way back in 5th, I used cruise control set at 65mph to keep my right foot factor out of it. I got 4mpg better driving in 4th, the engine was turning 2000rpm in 4th and 1200-1300 in 5th. The engine was lugging hard trying to maintain that speed in OD and had a higher throttle opening, in 4th, the engine was making enough torque to move its mass effortlessly. If I put it in 5th @55mph the car would drive along on the IAC without any throttle input, didn’t even need cruise control, that’s how they calculated the highway mpg rating from the factory. 4.10 gears fixed that.

[@UnityMotorSportsGarage]

Keith, you are exactly right.. My old 96 GT came with 2.73 gears 5th gear killed that car and like you said it would get better mileage on the highway in 4th.. I too put 4.10 gears in it and when I did.. 5th gear was now usable Andy

[@hotrodray6802]

Don't forget that cars built the last 20 yrs are required to pass smog for 100,000 miles with no maintenance except oil changes. High gearing assists that to happen. When modifications happen, computer programming is required

[@keithiverson6687]

@@UnityMotorSportsGarage driving off a vacuum gauge was eye opening to say the least, my project car is a 70 Wildcat with a 455, mild cam(223-230@110*lsa), TH400 and 3.42 gears, the sweet spot seems to be 50-60mph, it’ll pull 19-20” of vacuum and barely have to touch the throttle. The torque curve just starts to really get up on the cam at that rpm and fuel mileage is pretty good, around 15ish(haven’t been able to accurately measure it) without any major tuning.

[@johnshackelford6965]

Fryburger and Dulcich 221 260 Chevy Yea I just stole 🤪 🙃 it. I was in walking distance from Tommy Bosher shop. It's 383 I checked ✔️

[@reloadingfun]

My truck seems to run leaner from 10 inches of vacuum to 4.5 inches where powervalve opens up than it does from 10 inches and higher. The difference is 14.5:1 vs 13.0:1. Also when I go wide open throttle the ratio is pretty rich like 10:1 until the rpms pick up. This scenario is from 1500 rpm to 2000 rpm. I guess you could kind of describe it as a lugging situation. My cruising afr is about 13.5:1 at 12 inches of vacuum. Would changing air bleeds and emulsion jets be the cure to adjusting for narrow windows lime this?

[@JonnyMopar]

I’m digging this video Andy. 20mpg? I can’t wait to see that video.

[@kevinhall3003]

I had a 1978 Cordoba 360 2bbl Lean burn, swapped to a used 71 340 cam, and taller tires , got 32mpg @ 62 mph. Was the only Lean Burn That I know of that ran like a top ! and I drove the living crap out of it.

[@hotrodray6802]

🔔😎 2.41 gears: Remember, those cars had weak compression, retarded cam timing, wierd ignition curves, weak cams profiles, cats, restrictive exhaust systems, funky electronic carbs, heated intakes, sometimes lock up converters, and were designed to get corporate average fuel economy in laboratory conditions. State of the smog-art 🙄 . They sucked.

[@sdmarwan]

I have a stock 1990 Ford 5.0 except that I stripped the smog equipment and put on a Demon carburetor that I owned. It has a 66 primary jet and 78 secondary jet. What would be best for gas mileage?

[@jessesyfie7244]

Andy, a vacuum gauge is your friend, I use it all the time. The shit 8 to 1 compression of the early 70s just don't cut it. I'm doing a 350 rite now with a very short duration cam, about 6 degrees bigger than the stock 929 cam but going run 9.8 to 1 compression, may have to run 91 octane gas but that's my plan anyway. Should make it very snappy and hoping to put some timing in it.

[@mikeburnett7028]

Trouble finding your video on timing. I have a 402 bb Chevy with 9.5/1 compression. Any advice on timing setting? And do I use ported or manifold vacuum?

[@jesseduke694]

I know how I drive.... I drive like I'm the stunt driver for every episode of the Dukes of Hazard. Coming out of every corner or from every stop sign it's a drag race! Unless I see the popo then it's gramma goin to church on Sunday.

[@gulfy09]

Leaning things out and adding water injection helps mileage and torque

[@TheGraytOutdoors]

That was very educational. I learned more watching this then I did in 6 years of high school. Booger’s gas mileage got a lot better when the sending unit quit working. I actually need a smaller carb for Booger. Even a 600cfm is too much for a worn out 305 lol. You’ve inspired me to go out there and see if I can patch him together for a rip. Willie

[@UnityMotorSportsGarage]

Willie, I was thinking about you the other day when I took the Monkey for a ride! Thanks for the kind words.. hope all is well your way! Andy

[@Piggypongtheavgeek]

Foot control is the key. I have a vacuum gauge which helps.

[@joe-hp4nk]

I have the best of both worlds, a 454 connected to a NP440 my6 over drive transmission and a 3.08 rear gears. 1st 3.09:1 2nd 1.67:1 3rd 1:1 4th .73:1

[@427_FE]

Great video, Andy, and so were the previous ones you did on this subject. It would be nice if the Gear Vendor overdrives were more affordable so us C4-C6 owners could run the final drive we want, and still get a lower cruise rpm on long highway trips.

[@BuzzLOLOL]

Also, the GV doesn't give very much overdrive... about 20%... compared to 40 - 100% in stock automatic and manual trannies... Also, the draggy C6 sucks as much as 70 HP just to spin it over... while cars cruise at 15 - 30 HP...

[@markmccauley1923]

Andy, quick question. Will a larger main air bleed cause the mains to come in sooner? Thanks for the great carb videos.

[@steelassault262]

Maybe I should call you eccentric? Just to be different😉 Neat stuff Andy, and I will be interested in what you find out.

[@darylholloway4]

I’m a newbie with La 5.9 360 2bbl Ramcharger show me the way

[@davidpistek6241]

I subscribed because I like stuff that turns the gears in my head, lets me think about and learn stuff, although currently I'm far removed from carbs the fundamentals you talk about change constantly in current engines to optimize every possible situation, getting a carburetor car close to that docile must be a puzzle

[@UnityMotorSportsGarage]

Thanks David, it starts with finding the lean burn limit of your particular engine.. then you can taylor the carb circuits to suit the engine... I always try to think outside of the box Thanks for watching and the Sub! Andy

[@MoparMan-ff8fb]

Hi Andy , I know your a busy guy but appropriate all your time and knowledge with your videos and the time you have to answer my questions. Tell Mr. Vizard I really appreciate sharing his time and knowledge with us . at some point down the road will need your advice on picking a Holley carb for my 360 build . some people dont know that tire pressure and size/ width can affect your gas milage and if you drive a truck an open bed can cause wind drag . a bed cover helps I also noticed by taking the tailgate helps to if you have no bed cover

[@59vaughn]

Any one with a superstock t...gets my vote...😉😎😂

[@fritzfussell6190]

Hope you get 20mpgs or more with Casper hope there be more fuel economy tips coming

[@erenzoscroggins8056]

Great Info all around

[@davidpistek6241]

forced induction uses a lower compression ratio because a tc or sc stuffs the block

[@Texasmule]

I think 3.91 is a good gear ratio

[@CarsandCats]

I've been building carbs for over 30 years and built the 650 Demons on my roots blown Camaro. It got 13mpg average with 4.10 gears and a spool in the 9 inch and a 3500 stall 10 inch converter. It now gets 15mpg average with 3.50 gears and a 4200 stall 9.5 inch converter. The key is getting the part throttle cruise as lean as possible. I've been told you can't do this with a roots blower and those people are dead wrong. I use an AEM Wideband HEGO with datalogging and my cruise AFR is 15.0-15.2:1 and the plugs stay nice and clean. My WOT AFR is 11.8:1. The car runs high 10's @ 122mph on street tires through the mufflers and is driven to and from the track 30 miles one way. It weighs 3750lbs with driver, so no lightweight and it is a SBC.

[@genemanno1533]

All good points but guys watching your you tube are more than capable of figuring out the obvious. You need to show actual hardware combinations (jetting, IFR, AFR, timing limits. CFM, manifold configuration, ignition systems CD, HEI) you know things that make a difference. Casper might not be the best example since most guys don’t have that much motor. A small or big block with 4 barrel, small cam, aluminum street heads, intake headers after market distributor with your “changes” to achieve mileage/performance. Ford or Chevy, MOPAR don’t matter much all would be applicable.

[@UnityMotorSportsGarage]

Gene I have done those videos, I plan on doing more once Casper is up and running. I figured if I show folks how to do it on Casper it will be easier for guys who only have single four barrel carbs, etc. Thanks for watching, stay tuned because more is on the way! Andy

[@1112223333111]

1 secondary plate on the dominator looked open a bit...

[@adambatchelder4121]

Gear vendors overdrive is really nice for the older non overdrive transmission s

[@tetedemarc]

Very good explanations that all makes sense. Compression is free HP / TQ , more heat in combustion process = more push on your piston. I also like a direct drive transmission , I prefer a low 1st gear and a taller gear , the rest being handle by the converter. About gears I had a stock 440 in Road Runner swap a 2.76 to 3.55 and fuel economy was as good if not better . Consifering at cruising speed engine was running higher vacuum. I did run Holley 1050 Dominator for a season on 498 Mopar. I liked it a lot . I had made a quick cheat with a modified metering block gasket for street use that would open an extra air bleed and a stock block gasket for all out racing . It was a quick swap at the track. I'm sure I could have tweak accelerator pump , jets and power valve but it did work very good then. Today many carbs comes with replaceable air bleed . But the Mopurist I am ; I love my Thermoquad. Very good carburetor for any application. I even ran them as a pair on Weiand Tunnel. kzbin.info/www/bejne/emXFm56meLaig5o

[@jeffrey4547]

if i want mpg then i would get rise burner not a stroke 454

[@trailerparkcryptoking5213]

Does anyone make a throttle position sensor for a carb?