35 MPG 1966 Chevelle

[ksa8907]

Originally Posted by Hersbird

A 2013 Camaro 3.6 automatic actually gets 37.4 mpg on the old highway test before applying correction factors as nobody drives like that. Still that means that it gets even higher then 37.4 mpg steady state highway at 55mph.

i can confirm this, my CTS with the non-DI LY7 will give mid to high 30's MPG at 55mph. getting those 3800lbs up to speed is what kills it. that and i have an intermittent pinging that im sure is costing me mpg from poor power and knock retard.

[spacemanspif]

I'm not so sure on speed killing MPG but I have a very different experience with it. My Monte used to only get about 15-18 mpg with the original engine/trans and 3.73 gears. One year I needed to do a lot of driving for a summer job/internship so I found a 2.29 rear from another car and threw it in. Doing the math to see what RPM was 65-70 I was cruising at like 1600RPM and the engine was lugging and got terrible mileage. So I sped up to whatever speed was 2000RPM and jumped up to 25MPG consistently. So faster was more efficient but more so because of BSFC of the engine than the speed itself.

[mcrews]

This is the delima when people don't look at all the factors! Good job on your part to find the root cause!
Taller tires work but it is possible to go 'too tall' causing the engine to bog as you described.

[sgtlethargic]

Chaz's comments seem to contradict what I believe Aerohead has commented on before: that as long as the front end isn't too bad, the rear template aero stuff will work well. So, I plan on doing a 61 Ranchero and am wondering if I could get to 40, maybe even 50 mpg highway with a 1.6L Pinto engine and aero mods.

[Frank Lee]

I think you guys are somewhat over-enthusiastic. My 2.3/5mt has to be driven carefully to attain 35+ and my 2.3 a/ts will only get near 35 on the very best of days and my 2.0 a/t gets 35 driven "normally" and over 40 driven very carefully; these are all cars quite a lot smaller, lighter, have fwd, and are more aero than the Chevelle. Someone mentioned if one car got 27 then 35 should be easy... Nah, I disagree. 35 is a LONG way from 27.

Still, 30 would be a good achievement. And if it can get 35 I'd be happy to be wrong!

[JQmile]

Originally Posted by Frank Lee

I think you guys are somewhat over-enthusiastic. My 2.3/5mt has to be driven carefully to attain 35+ and my 2.3 a/ts will only get near 35 on the very best of days and my 2.0 a/t gets 35 driven "normally" and over 40 driven very carefully; these are all cars quite a lot smaller, lighter, have fwd, and are more aero than the Chevelle. Someone mentioned if one car got 27 then 35 should be easy... Nah, I disagree. 35 is a LONG way from 27.

Still, 30 would be a good achievement. And if it can get 35 I'd be happy to be wrong!

I dig the old school vibe, but the technology behind the new cars is insane.

I mentioned the 27 vs 35, but that was a V8 that got 27, and this guy is using a V6, which is where my guesstimation came from. Apples to Oranges.

[Hersbird]

I say the Camaro can get 37, I doubt the Chevelle will. Sometimes old cars with carbs would do better at certain rpm because they were tuned that way, or should I say weren't tuned properly in all throttle and load posisitions. I bet that is what was going on with the above mentioned Monte Carlo. Get the mixture and timing right at a low load 1600 rpm and it would have had better mpg then at 2000. That or it had an aftermarket cam in it. So many times people would over cam those old school engines.

[spacemanspif]

Originally Posted by Hersbird

I say the Camaro can get 37, I doubt the Chevelle will. Sometimes old cars with carbs would do better at certain rpm because they were tuned that way, or should I say weren't tuned properly in all throttle and load posisitions. I bet that is what was going on with the above mentioned Monte Carlo. Get the mixture and timing right at a low load 1600 rpm and it would have had better mpg then at 2000. That or it had an aftermarket cam in it. So many times people would over cam those old school engines.

The cam was stock but the SS did get a "hotter" cam than the regular Monte Carlos so maybe my sweet spot was a little higher with it being an SS. The carb and timing were adjusted by the computer so I should have had a more efficient set up compared to an old school completely mechanical set up. I'm not entirely sure an you can tune for a specific RPM when the cam shaft is still playing a major role in the efficiency equation.

I was under the assumption that the new Camaro aero was pretty terrible so I thought that the Chevelle might not be much worse. With an air dam to reduce under car turbulence I think the gap closes ever farther. I really didn't think old cars were THAT bad in the aero department.

[Hypermiler1995]

Originally Posted by spacemanspif

I was under the assumption that the new Camaro aero was pretty terrible so I thought that the Chevelle might not be much worse. With an air dam to reduce under car turbulence I think the gap closes ever farther. I really didn't think old cars were THAT bad in the aero department.

2010 camaro .36cd

60's-70's typical car .45cd+

[Hersbird]

Originally Posted by spacemanspif

The cam was stock but the SS did get a "hotter" cam than the regular Monte Carlos so maybe my sweet spot was a little higher with it being an SS. The carb and timing were adjusted by the computer so I should have had a more efficient set up compared to an old school completely mechanical set up. I'm not entirely sure an you can tune for a specific RPM when the cam shaft is still playing a major role in the efficiency equation.


I was under the assumption that the new Camaro aero was pretty terrible so I thought that the Chevelle might not be much worse. With an air dam to reduce under car turbulence I think the gap closes ever farther. I really didn't think old cars were THAT bad in the aero department.

Oh I thought you were talking about an early 70s Monte, the 80s shouldn't of had that problem but the problem they did have mid 80s was they couldn't figure out ememissions. Also the computers were programmed without the ability to learn so when you move it out of it's normal operating range it may have done bad things to the air/fuel or egr, etc.