Worth changing out 241s for 317s on LC engine?
Thread Starter
Joined: Nov 2004
Posts: 1,273
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From: Rochester, NY
Worth changing out 241s for 317s on LC engine? I've been debating swapping out my stock 241 heads for a set of hand ported 317 heads. I have an iron block 370, forged internals, LS6 cam, 9.5:1 compression with the 241 heads. It's an STS setup with a TC76. I went 136mph in my 4200lb GTO with this setup last year at 15psi.
My question is would it be worthwhile to go to the 317s? I figure it should drop my compression to about 8.5:1. I am running ARP headbolts now but I am switching to studs this season reguardless. My hope is that the 317s and studs will allow me to run more boost and make more power. I know the 317s should flow a little better but I'm not sure if it's worth it. My exhaust system only consists of stock GTO manis and the stock STS piping for now. Nothing really "stopped" me from running higher boost last year, it just seemed wise not to go higher than 15psi on pump and risking lifting the heads.
Thoughts?
Thanks
Adam
My question is would it be worthwhile to go to the 317s? I figure it should drop my compression to about 8.5:1. I am running ARP headbolts now but I am switching to studs this season reguardless. My hope is that the 317s and studs will allow me to run more boost and make more power. I know the 317s should flow a little better but I'm not sure if it's worth it. My exhaust system only consists of stock GTO manis and the stock STS piping for now. Nothing really "stopped" me from running higher boost last year, it just seemed wise not to go higher than 15psi on pump and risking lifting the heads.
Thoughts?
Thanks
Adam
)
Someone correct me if I am wrong but won't it drop the CR to about 9:1 not 8.5:1 ? Generally 317 castings lower about half a point I thought unless your 241's are milled but you said they were stock. Either way, I agree you should do it up. I am building my 370 right now with 8.5 CR and plan to boost up to 20psi on pump gas. I have a meth kit and will set it up to spray when the boost is up. Most power out of pump with about 8.5 IMO, boost to the moon!
If you have a 370 with 9.5:1 compression with LS1 heads, you will need to have -10cc pistons and 64cc chambers. Switching to 72cc LQ4 heads will give you ruffly 8.9:1 compression. For a SC car, I would say that is right on the border line. I myself would still do it 
Keith
Keith
