old motorhead

iTrader: (10)

LS3 vette has LT headers, no cats, and free flowing exhaust, 226/234/.580/114+2LSA cam, ported tbody, ported intake manifold, cold air intake, 4.10's, 6speed man trans. About 465 rwhp. I'm thinking that a bump in compression ratio to about 11.5:1 would result in more power, more mpg, and a smoother running engine. A little milling on the heads plus a thinner head gasket should do the trick. 93 octane is readily available. Is it worth the trouble? Might port the heads a little while it's apart. Your thoughts appreciated.

Avaric3

iTrader: (3)

if youre gonna port the heads too, i dont see why you wouldnt do it

Jimbo'sZO6

iTrader: (1)

Pretty good way to pick up 20+ rwhp! Go for it!

Jimbo

old motorhead

iTrader: (10)

Is 11.5:1 too little or too much with my setup? I'm trying to get it right the first time. I'm not completely sure it's even worth doing. Are ported LS3 heads a proven upgrade vs the stockers on a mild build? I'm sure a set of hogged out heads are good on an all out build, but I'm not so sure it's good for my motor.

See5

iTrader: (53)

A rule of thumb is one full point of compression is worth 4% hp.
The LS3 heads will like a skilled port job. The key is not to hog them out, particularly on the intake side.

old motorhead

iTrader: (10)

I'm just wondering if it's worth the time, trouble, and cash to port the heads for a mild build. I think it would be if I was starting with an LS1 or LS2, but I'm beginning to think that the LS3 heads are pretty good to start with. I haven't seen much info on ported LS3 heads for the street that are a big improvement over stock.

71CamaroLS1

Just as one data point: I've got a brand-new LS3, replacing my blown-up LS1, with the only internal mods being a Ragin-Racin Comp cams grind (227/235, .614/.621, 114 lsa), and .036 Cometic gaskets to raise compression to about 11.2. It made 459 RWHP, barely broken in, through a 12 bolt 4.11 rear end. With 92 octane fuel, I could only run about 24.5 degrees timing before I could hear occasional slight audible detonation. But the one run we did at 25.5 timing made no more power, so I'm guessing that 11.2 with 24.5 timing is about the optimum for our Oregon 92 octane.

From looking at a lot of different combos in the different forums, you just won't see a large improvement from porting LS3/L92 heads on a smaller displacement, moderately cammed combo. 10 HP, maybe 15 at best, and most of that near the top end of the RPM range where you won't notice it much. With a bigger cam and the forthcoming FAST intake, things might be different, of course.

WKMCD

iTrader: (2)

FWIW: The L92/LS3 heads love timing. I dropped the CR from 12:1 to 11.3:1 and was able to add 4-5 degrees of timing and picked up a bunch of HP. We had it up to 30 degrees but it left the dyno at 29 since it didn't make anymore power at 30. At 12:1 we couldn't run more than 25 without KR.

Just my $.02

jetblast

am i reading this right?, you lost power with the higher compression right? did you use the same fuel and octane for both set-ups? and how much hp did you loose? and last, what made you decide to drop the compression in the first place? don't you want to run 103 or better at the track anyways?

old motorhead

iTrader: (10)

Wow...everything I've read would indicate that an increase in c/r would be a good thing when adding a bigger cam to an LS3. In my case, the bigger cam is already there. I'm trying to decide if adding a little extra squeeze would be worth doing. I'd like to hear that there was a head upgrade worth doing along with the added c/r. Pulling the heads is a pretty good job on a vette. Not sure I want to do it if the end result is just a few hp.