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Discussion Starter #1
I am in the proccess of building a F.I. LT1 355 that is projected see about 8-10 lbs of boost (Vortec V-1). Based on my calculations, the SCR came in at 9.7:1 based on the following:

52cc head chambers (clean-up cut/ 2.00 & 1.60 valves using stock seats)
4.030 bore
.039 fel-pro 1074s (4.125 hole)
-20cc wisecos
5.7 rod
3.48 stroke
deck hieght of .015 (assumed based on factory spec;I will doulbe-check how far the piston sits in the hole once the s.b. is assembled)

Accepted theory is that this CR is too high for a F.I. motor. Is DCR more important than SCR? I am researching how to reduce CR without raplacing the pistons. Here's what i've theorized thus far:

-The original valve seats were used, if I have larger seats installed to drop the valves deeper into the chamber, would that significantly increase the chamber volume enough?

-The Fel-Pros are .039 thick. Is there a thicker gasket on the market that will hold up to this moderate amount of boost?

-Can a significant amount of head chamber material be removed on the LT1 heads to reduce SCR?

This is my first F.I. build and I definatley chose the wrong pistons. -20cc was not enough to get to my target 9:1 cr, but replacing them isn't an option. If i'm stuck with this CR, then i'll just have to reduce the boost accordingly and have it tuned accordingly.

Any insight/advice would be greatly apprecieated.

Cheers,
John
 

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I think you'll be OK with 9.7, but I'd run something to help get the AIT down (intercooler or alky/water injection)

I was running Wiseco 20 cc dish pistons in my last build with 51CC heads. Compression ratio of 10.0:1 with a hair under 14psi with an S-trim on alky injection. I used 93 oct pump gas and alkycontrol alky injection (w/ ww fluid) and it worked great. Pistons looked fine when I pulled the motor apart earlier this year.
 

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Discussion Starter #3
That's very reassuring; i'm looking at opening up the chambers a little more. I think I can get another 5-8cc's out of them. I'm still not 100% on the SCR, since I havne't measured the deck height with the Wiseco's installed. Did you measure yours; if so, what was the deck height?
 
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