What compression to run in a forged 346??
Thread Starter
Joined: Apr 2005
Posts: 1,014
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From: san marcos, TX
What compression to run in a forged 346?? So, I'm building a forged 346 motor. Whats a good street compression ratio to run with 14-16psi of boost and the ECS Paxton Novi 2000? I have a small blower cam and headers. I will also be running ported 6.0L 317 heads with 72cc combustion chambers, 6.125H-beams, and a unknown piston at this time(have not decided yet). I was thinking of around 9:1 or so....The one pistion I was looking at would give me 9.2:1...So lets here everyone's ideas...Steve's 99 Vette making 742rwhp with a 346ci and A&A old ATI DS1 setup at 14psi and he's my local competiton 
. I want to see 800rwhp guys
Also any piston preferences?? I've been looking at Mahle, Probe, Weisco, and Diamond...
. I want to see 800rwhp guys Also any piston preferences?? I've been looking at Mahle, Probe, Weisco, and Diamond...
Originally Posted by KAOS
8.5 or so. im goin to be runnin 9.27 but its a stout setup. they say the lower the better
Nate
TECH Addict
Joined: Jun 2005
Posts: 2,660
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From: England
In times past it was usual for supercharged engines to have a much reduced compression ratio to avoid detonation at full throttle. Such engines generally gained a reputation for heavy fuel consumption and poor response. These days supercharged engines run at compression ratios that would have been considered normal for naturally aspirated engines a few years ago and detonation is avoided by electronic control of ignition timing. Fuel efficiency and responsiveness in off-boost operation is therefore much improved. As an example the naturally aspirated Jaguar V12 of the 1970s ran at 9:1 compression ratio, produced 285 b.h.p. and required 97 octane fuel, yet the Jaguar XJR-V8 runs at the same compression ratio with 0.8 bar (12 p.s.i.) boost and needs only 95 octane fuel to produce nearly 100 b.h.p. more from 1.3 litres less capacity. That's progress.
I run 9.5:1 but I only run 7-8 psi. Soon I will be running 10-12psi though! I used Diamond pistons too. I forget the specs on them though because I had someone else build it.
Good luck running 16psi with a 346ci and pump gas (no meth) at 9.5:1.
I think 346ci (9-9.5:1) + 16psi = 100-104 unleaded.
This other vette which you speak, what is his combo and what does the car run at the track? 750rwhp is great, so I assume he traps over 140mph?
I think 346ci (9-9.5:1) + 16psi = 100-104 unleaded.
This other vette which you speak, what is his combo and what does the car run at the track? 750rwhp is great, so I assume he traps over 140mph?
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Thread Starter
Joined: Apr 2005
Posts: 1,014
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From: san marcos, TX
he's got a 220/224 cam, LS6 heads, meth and an A&A shortblock with diamond pistons. He's only been to the track once and sucks as a driver. I watched his smoke the tires in all 4 gears(street tires), by then he just gave up... He needs some drag radials or ET streets. Neither one of us is much into drag racing though. I prob will add meth with this build up as well for a little added safety....last time I was traping 130mph on street tires spinning through 3rd gear...
He needs some drag radials or ET streets. Neither one of us is much into drag racing though. I prob will add meth with this build up as well for a little added safety....last time I was traping 130mph on street tires spinning through 3rd gear... Last edited by chriswtx; Apr 11, 2006 at 09:42 AM.
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