V-10 Killer

iTrader: (22)

Ideally, if you're shooting for a certain compression ratio, does larger head cc have an advantage or does modifying the piston for the task? I've read a little about using a head gasket that gives you a PTH clearance of about .040", does this sound right?

At what level is the difference noticable/negligable?

I'm asking mainly because I'm looking to change my CR and want to know if it'd be better to replace the pistons or have the head cc's re-worked.

Thanks

chrisfrost

iTrader: (8)

Yes obtaining You're target static compression while having as large a combustion chamber as possible and at the same time having a quench from .032" to .038" with .033-4" being the best quench and still being safe from the piston hitting the head . Actually lets say for instance You have flat tops and stock heads with 66.67cc c ch with stock static ratio of 10.1/1 and You want 11/1 so You install thinner gaskets and You mill the heads some . This change has only gained You 11 hp . In another example You maximize You're flow as in cyl head porting (cnc) and intake tb and You lower You're compression ratio via dished pistons You could gain as much as maybe 25 hp without changing cam . Yet another thought is to either install a water inj kit or a meth kit and cool things down and gain some hp or something I'm going to try is run My A/C cold air (37-40 deg) directly into the intake an engine theoretically should be able to gain maybe 15% or so hp which could be as much as 50 hp . From what I've noticed driving My own vehicles is this is pretty accurate the only problem is You would'nt be gaining anything when the temp outside was really cold but who cares ?

KCS

iTrader: (20)

Small chambers usually work best.

IMHO, the best way to increase compression ratio is with a longer stroke!

V-10 Killer

iTrader: (22)

Hmm, one vote for large cc head, one vote for small cc head.
I'll give a little more info on what I have and am after, but I was mainly looking for a general rule.
I have a SDPC LS2 402, Diamond -14cc dished pistons, ET 245 heads w/59cc chambers, if I remember right, the piston was coming ~.018" above the deck. I had .051" MLS gaskets. That came out to about 11.3:1 and worked great.

My new target though is closer to high 9's to 10:1 compression for a FI build. I can't run more than 15psi due to tuning constraints, and don't want to either way on an aluminum block so I think that gives me my best drivability compromise. I e-mailed ET Heads about cleaning up the heads and re-working the chambers to a bigger cc volume but didn't get a response. I see Weisco makes -20 and -32cc pistons but that would seem to hit outside my targets. Diamond makes a -28cc which looks like it would put me on target. Or I could re-work or swap the heads to around a 72cc head and that would do the same thing. Either way, I need to add about 14cc to hit my target. I was just wondering which way would make for most efficient combustion.

redtan

iTrader: (5)

Heh I'm gonna go right in the middle. I wouldn't worry so much about size but shape and efficiency. The right combustion chamber shape, valve angle, valve de-shrouding will all have more benefit than just size.

bww3588

iTrader: (49)

The best way is to use the largest chamber possible to minimize valve shroud and promote air flow.

chrisfrost

iTrader: (8)

If You Google "gas direct inj" and click on the wiki and read the basic info they have somewhere down that page it mentions I believe a Toyota engine with gdi running 13 to 1 static compression and there are some good ideas on that page