Early heads on late short block work with e85?

v8440

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Title says it all-I live in Iowa now, and e85 is everywhere. Would putting early small chamber heads on a late short block work if you fed it only e85?
 

Caddylackn

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I can see that this may work if you can prevent all detonation with the appropriate E85 timing and fueling curve. If these are cast pistons, piston longevity could be a problem. I would check piston to valve clearance on any aftermarket cam. You might upgrade to a better head gasket, I think the stock head gasket will be the weak link.

If this was a daily driver in something I cared about I would use forged pistons and ARP rod bolts.
 

v8440

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Just a basically stock motor (with new decent timing set installed of course) in a buick apollo. Stock cast pistons take nitrous and moderate boost just fine, so I'm figuring that they'll take high static compression with no detonation as well. Am I thinking straight here?
 

Darius

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I can’t say from experience that your approach would work, but I’ve bet my engine it will.

In my thread (Showing you my junk ….”) my build uses early heads but with forged pistons + twin turbos. The entire fuel system was specked to handle
the high volume of e85 necessary to
meet my goals.
The engine was broken in on a run in stand so it hasn’t yet been under load.
If you keep your timing and fuel ratios in line my bet is you’d be fine. Again, no personal experience, but a calculated guess!

bro. d
 

v8440

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That's kinda what I thought. I have lots of personal experience with beating the hell out of another brand's factory cast pistons (mopar), with good success. I don't figure cadillac's pistons would be cheap junk as stock pistons go.
 

Cadillac Kid 1

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You will definitely find the weakest link. If the only thing you are doing is increasing the compression and not improving airflow via cam, porting, carburetion, the actual increase in power (due to the increased compression will be minimal (about 8-1/2%). That said, with small chamber heads on flat top pistons, your cam specs are going to be limited. you can pick up a whole lot more power by sticking with the large chamber heads and going to some head work and a cam.
Greg Surfas
 

v8440

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That's true, though it will be snappier and more torquey. The small chamber heads are lying around the shop (actually still on another engine).
 

robocop

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What vehicle(s) do you drive?
1987 Cutlass Supreme 2 door with 500 Cad/Turbo 40
My machinist, Reg, RIP built many dozens of airboat engines for the tourist industry in the Everglades. He said the Cad rod bolts are fine, he'd rebuild abused 500s with snapped rods but the big end was still on the crank. Many years ago when Hot Rod magazine built the Bad Seed, the 500 Cad in a Chevette, they put small chamber heads on late 500 pistons. They figured they had around a 12:1 compression ratio. I would presume they used race gas but eventually they cracked a piston. On E85 I don't think detonation will be a problem. Its piston to valve clearance.
 

v8440

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I can check piston to valve clearance with no problem, and fly cut the pistons still in the engine if needed. I did it several years ago with a friend's 402 bbc, still runs fine today.
 

Caddylackn

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My confidence that this would work would be directly proportional to the amount of spare parts I had. If you have a spare short block, I would say go for it.
If you just spent big bucks rebuilding this one, I would do some more research.

Although cast pistons have been known to take a few hundred hits of nitrous, that is only about 30 minutes of total run time under those pressures. What nitrous cylinder pressures are compared to 12:1 CR pressures on E85 are? IDK

I would like to see this tested.
 

v8440

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No doubt cylinder pressures with nitrous are WAY WAY higher than cylinder pressures from a moderately high static compression ratio. If you've ever driven a car on nitrous I think you would agree. You're right about the duration of time though.
 

robocop

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What vehicle(s) do you drive?
1987 Cutlass Supreme 2 door with 500 Cad/Turbo 40
The problem with the nitrous is getting the fuel mixture and distribution right so you don't burn a hole in a piston. Thats much less likely with the E85.
 
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