SBC for Gas Mileage

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bob w

Still crazy after all these years!
Joined
Jan 2, 2008
Messages
13,151
Location
Stillwater, MN
As my S-10 wears out I'm thinking of building a '48-'54 Chevy pickup for a daily driver. I'd like to average 20mpg, so I don't take too big a beating at the gas pump. Also, I want to have a truck I can service, meaning no computers or exotic electronics. So, here's the question: What engine would you build, realizing the truck will occasionally pull a trailer with a 2,000lb race car on it? I have 283, 327, 350 & 400 blocks and cranks. Tell me what size engine, compression, cam, heads, carb, intake, etc. you would use. I'll use either an overdrive automatic or a 5 speed and want to cruise at 60mph at around 2,000rpm. Any tricks you have for getting a good mileage combination would be appreciated.
 
Milage!

If it's dependability & mileage u're after... then I'd go with a 283 2-barrel. Great motor... smaller displacement & smaller carb, headers, high rear gear... outta make a great cruiser. Tranny is u're choice... I like OD autos.

BoB
 
I've been thinkin' the same thing-here's my thoughts...

Would be E85 fuel-

*12-13:1 compression
*vortec heads, flat milled to get smallest chambers possible without causing intake alignment problems.
*flat-top pistons (if possible to get the compression I want-don't want domes hindering flame travel)
*custom torquey hydraulic roller cam to cruise @ appr 1600-1800 rpm and take advantage of E85 fuel.
*MSD ignition
*Performer Air-Gap intake & Edelbrock 1414 E85 carb (if they ever release it)
*1 5/8 headers
*1.6 rockers
*rollerize as much of valvetrain as possible
*bearing clearances slightly on the tight side so I can run 5w-20 synthetic oil
*coated pistons
*electric fan
*700r4 tranny

Was thinking of doing this in a S-10 pickup. Engine would probably have 450 lb-ft of torque, but if you keep your foot out of it, I think you could get 30 mpg freeway (2wd) or 25 mpg (4wd).

Let's hear some opinions-
 
In general anything you do to increase power will cost you mileage and vice versa..

However there was something called the Crower Mileage System that Was basically a Atkinson cycle conversion for SBC's. Would probably have worked with variable valve timing.

All the foreign cars have variable valve timing and many of them have variations of the Atkinson cycle. I can assure you this is the wave of the future.

VVT is probably something that most guys are not yet ready to enbrace in Rods.

So that leaves you with the small displacement option.

Now one way to get around the loss of low speed torque is to put a variable pitch Stator from a Buick 400 trans in a 400 trans that bolts on a SBC. I am not sure if that can be done with a lock up torque converter.

Another option would be to use a high compression engine with bi fuel technology. Have E85 as the power fuel and gasoline as the cruise fuel. Secondaries coul be plumbed for E5 and primaries on gasoline. Might require having the power circuit in the primary sourced from E85.

It could all be done but I seriously doubt that most guys would want to go through the effort to do it.
 
Tripper & Adam, you are talking about the 2 options I'm debating although I'm not sure about E85. It's available in MN but not so widely available travelling. Flat tops and Vortec heads with the max. compression on 87 octane gas was kinda what I was thinking. Hadn't thought about reducing internal engine friction much. That is a good idea.
Adam, were you thinking a 350? I'm hoping to get the same mileage with a bulky, old truck body with a V8 that I now get with a sleeker, V6 S-10. A pretty tall order.
Cob, you are right, VVT and electronic fuel control add to engine efficiency. A 5 or 6 speed would eliminate the fuel an automatic transmission sucks up.
Do you think going 60mph instead of 70mph in a boxy old truck will save a couple mpg? I can't get too exotic cuz I won't live long enough to get the money back in improved gas mileage!
 
engines

My uncle used to commute from northeast ohio to indianapolis for tech school in the seventies. his tried and true combo was a 283 bottom and a 350 top. when i mean top i mean the heads, intake, cam and a 500cfm 2B. these were not new parts , just refurbished junk he collected at home and school. i thought this was kind of a negative myself putting 76cc comb. chamber heads on this small bottom, but the cam made it work well with the larger valves and chamber, a stock cam. It was some where around .360-.390 , 194 dur. Lots of low end torque and takes the revs. He was getting 25-28 mpg back in the 70's , with a heavy 67 chevelle, 4.10's, turbo 400., oh the parasitic loss of the 400. The car was sold to my father years later and he also ran this setup ( 5 different engines ) till he sold the car , by then alot of good running 283's were sucked up. It was all mostly free and bartered junk. I also agree with the other fellows. Choose your trans and rear gear wisely and you will be rewarded.
 
Yeah, probably 350. Mainly just because they're so easy to find. The problem w/ going to a real small engine like a 283 or so is that it is hard to find heads that flow good for that small of a bore. The smaller the bore is, the more you are shrouding one side of both valves and limiting air flow into (and out of) the chamber. If you go real big with the bore (like a 400), you are then adding a slightly higher risk of detonation if you are on the edge with the timing and trying to pull a trailer. The farther it is across the top of the piston, it becomes harder and harder to burn the fuel efficiently without a second little flame starting in a far off corner of the combustion chamber when you don't want one=detonation.

I had a 406 in a 2wd S-10 a couple years ago. 9.3 compression, vortec heads, Comp XE268 cam, performer rpm intake, and Holley dbl-pumper. Very torquey hot rod engine and ran it on 87 octane. Don't know if I would trust it to tow with out detonating, though...

I would say about 9:1 compression max for towing with vortec heads. Any more, you'll just have to retard it so it doesn't knock when you tow. I would go with the vortec heads and polish the chambers in the head so they are a smooth surface, go with 1.6 rockers, and zero deck the block so the flat top pistons come up flush with the top. Use no thicker than a .040 or .041 thick head gasket to keep a good amount of quench. I would at least ceramic coat the top of the pistons to help with combustion as much as possible.

If you haven't used the vortecs before, any valve lift over about .425 or so and you should have them machined for higher lift and smaller seal. Also keeep the timing to around 32-no more. Efficient heads-don't need a ton of timing. I'll see what else I can think of later...
 
Thanks guys, you gave me some good ideas. Now, to find a good Chevy pickup within a reasonable distance. Maybe I can find a project someone gave up on.
 
Dang it 24dodge! Now you're putting me to the test. That Chevy truck is just what I'm looking for. And, less than 100 miles from where I'm sitting right now.
 
24dodge, I just forwarded the first Chevy truck ad to my good friend who is a specialist in '40 Chevy trucks. I just received my tax refund and actually could buy one now, even though it would be next winter before I would start on it.
 

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