I've got a a 408 currently running 317 heads and -20cc pistons that are giving me 9.1:1 compression as I thought I was going to be running pump gas. Now the motor is back apart and I'm wanting to raise compression as much as I can to take advantage of E85. For the best bang for the buck should I just install new pistons ($775) to get 11:1 compression and keep running my 317 heads. Or should I just buy an aftermarket head like the PRC 247 and only have 9.7:1 or so since I would still have the deep dish piston. I could do heads and pistons but then were talking $3,000 which i'd try to keep from.

 

how much boost are you planning on running?

 

I would do heads before pistons. I am kind of in your same boat. I built my motor for pump gas and I calculated a 9.06:1 compression with my 72cc AFR's and my pistons. Now I am really liking to go E85 and maybe raise my compression, but
A) I do not want to put new pistons in my engine
B) I don't want to get rid of my nice AFR's. lol

So my plan is that I will just stay at my compression ratio and just run more boost I guess, so I am planning my next turbo setup for that. I guess only thing I am worried about is that with the lower compression I wouldn't be able to spool the turbo very well.

 

Like you agreed with me on in the other thread, the right cam timing and you'll have no problem, a simple advance of the ICL might be all it would need to light off if you found it hard to build boost. The tune can also be hopped up to help with spool also.

You'll have no problem and if you do just ask what you can do to fix it.

SCIDAV- I would mill the heads. Just make sure you have proper PTV and the right length push rods.

 

Put a 243 on it.

 

I would do with an Aftermarket Head with a thick deck if you have the cash. If not mill the 317s.

 

i,m in the same situation as 93 camaro have built 408 with stock 241s currently running 9.5 to 1 compression my mechanic who seemed to think it would work with e85 has purchased afr 230cc 72cc heads to go on when new 88mm turbo is fitted!!!maybe his plan is extra boost will make up for it!!! had people at drags the other day telling me to go 62cc chambers to take advantage of the e85 better!!! i trust my mechanic as they are very good!!! is it possible to run a thinner head gasket that still seals well that would raise compression a tad??? cheers

 

Can't really mill the 317s that will rid them of ever more deck height. I plan on doing up to 25 psi or so. I could live with under 20 though. My number 7 and 8 pistons need replaced now anyway, so i'm sure i'll just go with them all. Still leaves the heads though. Wonder if its really worth it. Mostly off boost on the street.

 

25 psi or less i'm sure.

 

I was in the exact same boat as you not to long ago, i wanted a boosted 408 to run off of 93 octane then as prices started creaping up on me and fuel prices rising all the time I switched my pistons. I went from going to have 9.3.1 compression to 10.5.1 compression now going to be running e85. I don't plan on going up to 25 pounds of boost but about 22 is by far the max I will ever see who knows, maybe less depending on how radical it gets.lol

 

You don't need to raise compression to take advantage of E85, just turn up the boost. Besides, you will make enough power at any compression on that motor to push the 317s off.