If I go from 10.1 (stock) to 11.1 will I pick a noticeable hp?? If so How much??
Just A guess is fine..

 

I wouldn't recomend increasing the compression unless you have a cam with a lot of overlap, or will be running race gas.

 

Irrelative to the question asked.

On average you'll see a 4% increase in power. Higher octane pump gas is sufficient at that level (91 Octane and up).
A tight quench is preferable, something in the .030>.038 range.

 

There is way to much to learn about compression and to many factors to just say if I go from 10:! to 11:1 will I gain power.
The easy answer is Yes. However it is only a yes if you have other supporting mods.
You will need a better fuel for starters.
I have seen a few guys switch cams but they didn't have enough money for heads. Therefore they threw a set of 5.3's on their car and it raised compression to around 10.8:1
Now they have a better cam, hopefully a tune with the addition of a cam and new heads. And in compairing their current setup to the same setup and stock LS1 heads they probally gained some power.
Noticeable HP ???
If 10 HP is noticeable then I am sure you could get a extra 10 ponies.

 

Cool thanx for the info...

 

I agree with PREDATOR!
About 4%, so a 300 rwhp car will add 12 rwhp by just removing stock heads and milling.
I would start by installing a thinner head gasket then mill to get the correct compression, this will make more power.

 

where do I get thinner head gaskets??

 

cosmetic has them.
I would not shave my LS1 heads, I would just buy a set of used 5.3 heads.
Later on down the road if you decide to add a cam you will beable to use a bigger cam without P/V issue's.
If you shave the LS1 heads a ton to get compression to 11:1 you wont beable to use as large of a cam in the future.

 

Cometic has them in different increment from .040 up. On a stock shorblock for street, .045 is a good medium.

I would not swap for a STOCK 5.3L head. While you will increase compression, the flow #'s of the 5.3 are much lower than an LS1 head.
A ported stage 2, 5.3L would be real good.

BTW, you only need a ~63 cc LS1 to get ~11.0:1 with .045 gasket.
.006 mill for every 1 cc.
So basically a ~.20 mill max which by any means is not a ton of mill.

 

I've heard that if you swap the exhaust valve in the 5.3's, they will flow as well as LS1's. So, if I mill my stock LS1 heads .20, and get that .045 gasket, would they be able to clear with, say, a G5X2 on a 114?

 

Not without flycutting the pistons. Theses big cams were designed with stock heads and stock gasket thickness for clearance.

 

Maybe but before my post his thread was being ignored.

 

I had my Ls1 heads milled .030, are you saying this is a mistake?? I have forged pistons with 2cc valve reliefs....The cam is a 609 lift cam???

 

Ah, gotcha. Back to the drawing board...

 

I think we should make you "Thread savior Director"

 

???????????DID i MAKE A MISTAKE????????????

 

Nope just joking with CAL

 

ALLRIGHT!!!woooohooooo!!!!!!!!