thunderkitt3n

hey guys, I blew up my ls1 earlier this spring and have been doing research on what to do next as far as motor options. I plan on building a turbo motor and I want to have a motor capable of 1000rwhp on kill mode, but will it will mostly see between 6 to 700rwhp. I mainly want room to grow. My current ls1 has prc stage 2.5 5.3 heads with a 67cc chamber, as they sit they aren't very boost friendly. I have always wanted to do a 370 swap but am caught in a tough position with those heads. I'm trying to keep this on a budget so basically I see three options.

1 is to keep use the prc's and run them on my 5.7 and put dished pistons in.

2 is to do a 370 with with -25cc pistons and use the prc's.

or 3 is to do a 370 and use just stock 317's.

I like option 2 because i can use head studs and not worry about the heads lifting, i'm just not sure if it makes sense to use high comp heads and make up for it with super dished pistons. i like option one because its cheapest but i'm afraid to crack the aluminum block.

what do you guys think? i've been going back and fourth on all these options all summer now and really want to start building and be ready for next spring.

thanks alot in advance

TyCZ28

id run the PRC heads personally. People are running higher compression more frequently on boosted motors these days. on a 370 with ls9 gaskets a -10cc dish would net around a 9.5:1 compression ratio and a -4cc flat top around 10.0:1 both of these would be ok for boost with proper fueling. your looking at roughly half a point of compression fi that going from your heads to a 317

HCI2000SS

iTrader: (2)

I run the PRC stage 2.5/5.3 heads on a 370 LQ9 with a pretty big cam and with 11.5:1 compression. I was told I could run about 7 psi max with this setup. The car runs awesome n/a and on nitrous it runs like a beast.

TyCZ28

Your probably running a Domed piston and or have your heads milled more than the 67cc the OP is claiming his heads are cut to.

HCI2000SS

iTrader: (2)

I missed the fact that the heads were 67cc. I run flat top Diamond pistons on a 61cc

thunderkitt3n

Shoot, sorry guys, I ment my prc's are 59cc chambers, i'm not sure why I was thinking 67. That's why I'd have to run the -25 cc dished pistons and if I remember right it brought me down in the mid 9's for cr. I haven't come across a set up like this before and so I'm questioning it. It seems kinda halfa***d but it's a cheap way to use a better head if it would work.

HCI2000SS

iTrader: (2)

Are you sure it will bring the compression down that much?

TyCZ28

10.2:1 roughly on a -11cc piston. depends on how much boost your wanting to run and what kind of fuel.

thunderkitt3n

I get 9.3:1 when I calculate it with the -25 cc pistons. I'm not sure how much boost I'll be running since I think the pressure depends on the flow resistance of the motor, but I plan on running e85 like I was before my ls1 let go. If I had to guess based on similar builds I would think my boost would be around 17 on kill and around 10 on a street tune. I'm looking at a TSP short block and they offer the -25 piston that's why I was looking into that. This is my first turbo build so I don't actually KNOW anything lol, just going off what I read on this forum.

Thanks again for the responses.

HCI2000SS

iTrader: (2)

Also check out Thompson Motorsports for shortblocks. When I got mine it was the best price I could find at the time

thunderkitt3n

yeah i have been looking into tsp, atk, and tms shortblocks and for my needs right now tsp is the cheapest. its funny how you can't even build your own motor for what you can go buy a short block for. the cost of machining to take a 6.0 to a 370 and assemble it with head and main studs and balancing bring it right up to what a brand new one cost from one of the above listed companys.

so what do you guys think about using a -25cc piston with a 59cc chamber head? is that just cheating or should i sell the prc's and go with a stock 317 head and hope not to lift the head? I dont really want to fork over the cash for prc 6.0 heads.

what do you guys think is a good cr for boost build? anything less then 10.5?

JakeFusion

iTrader: (7)

What compression are you shooting for? I'm going to be running a Procharger F1D on my 11.2:1 motor at around 10-12PSI with Methanol injection.

But, I plan to move to a built shortblock. And I have 62cc heads and will be running an -11cc Wiseco for 9.9:1 with a .045" gasket and pistons out of the hole .010". I'll up the boost to 15-16psi.

I know turbos like a little less compression than a centrifugal supercharger, but I'd aim for 8.5:1 or 9.0:1. A little more compression helps off boost.

thunderkitt3n

I'm thinking any cr between 9.0 and 9.5, i'm just unsure about using high compression heads and putting in a big dished piston. Will I lose any reliability with a set up like that? I don't see many people running a huge dish like that

JakeFusion

iTrader: (7)

Wisecos are a reverse dome with a quench pad. You'll be fine.

imma_stocker

iTrader: (19)

Higher than 9.0 SCR with boost, I highly suggest E85 or injection to fight detonation.