Helping a buddy with a build sheet for his 376. He wants to keep it n/a and would like the compression around 12.5. He has a set of 243 and the 317 that came with the 6.0 he got. Were thinking l92's, but since he has the 2 sets of heads to choose from, where wondering if either would work just as well with a little machine work. Any advise?

 

Wow 12.5? That's a lot of milling.

 

Not possible? What would be the ideal CR for a 376? And using what head to achieve it?

 

What is he doing with the truck? CR between 10.0:1 - 11.0:1 would be way more realistic. 12.5:1 is going to be dedicated racing fuel or ethanol.

 

Its actually a swap into a chevelle station wagon. Hes aiming for 500 hp

 

He don't need 12.5:1 CR to do that.

 

So 11.1 what heads would you recommend?

 

You dont want to get it that high.
My piston/head/gasket combo on my 370 is 11.0-11.1, I would shoot for that myself.
I run prc ls6 2.5s pretty good budget head for what you get them for.

 

I was thinking the 317's since it has bigger valves then the 243's and just have them milled down to raise compression...? Or just use the smaller combustion chambered heads and raise the compression without milling?? Or would the bigger bore need more intake then the 243's could flow?

 

243 and 317 have same valve and intake runner sizes. 500hp NA on cathedral port heads will be a chore. Square port or bust.