1970's "30mpg" V8 cams, big car, w/14:1 CR on 87oct

[slowmover]

The man at Isky knew his stuff around mpg.

[freebeard]

https://www.google.com/search?q=ed+iskenderian

[drainoil]

Years ago when I bought my old CVX-18, I found the seller had installed a Holley Economaster carb. It became a bargaining issue as it was not for marine use.

[cosmick]

That carb was a joke, as Holley themselves have publicly admitted that they can't beat the Rochester's triple venturis for MPG. That being the case, unless you're going for multiple inline DualJets, there's little reason to use anything other than a QuadraJet if sequential port EFI isn't in the cards.

[aerohead]

Originally Posted by stillsearching

YES! That sounds right, 1932 Vicky. I wanted to say 32 or 34. That helps narrow it down. We probably read the same article then, and hopefully you'll agree with me the assessment was "yeah it kinda DOES work" which is why it remains interesting to me today, how it would stack up against either modern improvements, or whether it could be used alongside steep overdrives, fuel injection and similar.

And yes I had interests in those other things too, was Yunick onto something or was he a fraud, etc. That was running in Popular Science and such too.

CAR and DRIVER dispatched two of their techies to Smokey's digs.On their outing,Smoky's rig burned a piston and ended the test drive.The C and D guys as I recall,were not impressed and made comments not flattering to Mr.Yunick.

[2HXs]

Back in the day, like the first weeks this site was started, I was a member here...don't know "who I was" or what email I used...I'm old, so now I'm 2HXs. I don't have a problem rebumping a bumped necro thread either.
Also back in the day I used some of these fancy cams, water injection yada yada. The cams actually worked well, the H2O injection sort of did.
Speaking of back in the day mpg boosters... have a look into this book
Performance with Economy by David Vizard(not enough post to link ya direct)
Very applicable info and some that isn't you judge.
It deals with some of the stuff discussed here and now in an ancient way.
It's available at ama...n
Once upon a time I used the books info and DC/MoparPerf parts to build an awesome 50mpg 83 Charger. Great mpg and unusually quick car that could smoke many of the 80's-90's performance cars. Would hold it's own today as a matter of fact.
Pardon my hasty reintro

[stillsearching]

A bit of thread necromancy but i'd totally lost my password and haven't been on the internet much due to RL needs.

This topic remains a thorn in my side/path not traveled until such time as i'm ever able to see someone test an engine for BSFC and torque values. I'm aware as time goes on most interest in this will decrease but i'm a completionist. :^) Not everyone in the future will be able to swap in a 2020 era powertrain just to get 1980's results.

Originally Posted by Hersbird

Put that 30 mpg claim through the current epa test and I bet it would come out something like 14 city 18 highway. 30 mpg would have been at 40 mph with gearing set to just have shifted into high.

I am still thinking this is completely missing the point. Nobody else was getting 25mpg with a 1932 Ford, let alone with a carburetor, 3 speed transmission, no lockup, no overdrive. The far more aerodynamic (0.31 I think) Chevy Caprice I had going 1600rpm in 4th overdrive on steel axle ratio could get that - but even that powertrain swapped into a 1932 Ford would have dropped from the aerodynamic load. That makes me wonder what that special cam might get swapped into the newer aerodynamic Caprice. :^)


FWIW the pointed out issue suggests it might be correct: backissues.com - Hot Rod September 1981 - Product Details - I wish someone could get one and scan in a PDF to share here, then other people could read the article and come to their own conclusions. Or/and to 100% verify that it was a Miller cycle conversion kit, if that's actually what it was. (even though it sounds about right) It remains interesting to me because i'm not aware of any other Miller cycle engines or conversion kits for larger engines that you might have in a large sedan, wagon, or pickup.

Maybe one in a big block could still tow something worthwhile and get better than normal BSFC while doing it without the cost of a 6 speed transmission and VVT? It sounds like Mazda is maybe doing something along the same route with their Skyactiv-G system running 13:1 compression on 87 octane.


To Changzuki's scans... unfortunately that is absolutely not what I am talking about. :-/ I do not see any mention of maintaining an "up to 12.5:1 compression ratio or even more on pump gas" which was part of the marketing at the time - making 1960's high compression gas guzzlers into efficient MPG mobiles with just a camshaft change. They were not high lift RV cams, long duration race cams, or high compression racing cams.

[cosmick]

Any dyno in the country can get you bsfc at wot, but we don't cruise at wot. Likewise torque numbers. Nothing worthwhile /valuable can happen without just getting a car, putting an engine in it, and experimenting using scientific method.
Cruising at the rpm of torque peak at wot was debunked decades ago, and choosing a cam over an overdrive is senseless. You can get a used od auto for the same money, with results that are better in every way.
Anyone serious about this needs to go find and buy a really old car they like, then report back, so we can discuss what engine and gearing to swap into it.

[serialk11r]

Interesting thread revive.

It should be true. If I understand how carburetors work, the cam profile matters much less for combustion efficiency than with MPFI, since the fuel has so much time to vaporize.

High static compression ratio plus late intake valve closure is exactly what the Prius and many other engines today do. The reason this is a great idea for modding an engine if you can tolerate the loss of low end torque is because at high engine speeds you gain the volumetric efficiency back and actually make more power.

The strange thing is that with a carbureted engine, with cams that big you would expect a lot of fuel to be blown out the exhaust and wasted. My guess is that they kept the exhaust cam reasonable and not open early to prevent that.

The reason you have never heard of this becoming used widely is precisely the fact that you are losing a crapload of low end power. If you're bleeding off half the charge, you're basically getting the fuel economy of an engine half the size, and also have the torque of an engine half the size. VVT is nice because you can bleed off the charge at low throttle, then adjust the cam back to get your torque back when you need it.

[cosmick]

So much to comment on there. The Prius is a lousy reference because it's 1.5L is an old design that was relatively inefficient even when new.
Maximizing any engine's low-RPM torque seems bad for emissions, based solely on the evidence of trends of new cars over the last many years, but torque engines that rev are a lot more fun to drive than engines with more peak HP but less average HP because they have no torque. Sure, a loose torque converter and deep gears can help partially offset that, but the result is still harder to live with. Put the loose converter behind a torque engine that revs, and you have a recipe for excellent fun, with half- throttle tire shredding.
Mileage and emissions don't matter if the car isn't a joy to drive, every mile you drive it. So you may end up at 30 MPG rather than 70, but that still beats the 10 MPG of the musclecar glory years around 1970. And those still were not truly fast, not like today's muscle that can top 30 MPG.
The biggest problem with vvt is that it can't do what is needed. Variable duratuon lifters are a lot closer to ideal.
Exhaust opening, you want early for high rpm power, late for low rpm torque. The same for intake opening. And the exact opposite for valve closing points.
Getting an old school Chevy 350 to make 400 HP and do 30 MPG is easy, no tricks required. With variable duration lifters, 450 HP and 35 MPG looks realistic.
If you could cut one in half, you would get 225 HP, but not 70 MPG. Turbo that up to 450 HP, it should still do more than 35 MPG, so there is merit to boosting smaller engines, but MPG is mostly about aero drag, and for an old V8 car, the rest of it is a mix of dialing in the fuel delivery and spark timing, and getting the cruise rpm down.
And in case i haven't noted it recently, the wilder the cam, the more cruise RPM it needs. That hurts MPG. You want power with your fuel economy? Start with good heads, then add a turbo. That's why the whole world is in love with the LSx. You can have a thousand horsepower with 30 miles per gallon and clean emissions. Work at it, it can do 35 miles per gallon. If you want more MPG and less power, go buy a horse.