well for one thing the rectangular port genIV heads (L92, L99, L76 ,LY6, LS3, etc.) aren't "interchangable" with the genIII's w/o also changing the intake. They also aren't designed for any motors under 6.0L w/o cutting valve reliefs in the block.

 

if im not mistaken the 05+ L33 or 5.3 HO came with 243s

 

I've got a set of 035's on the silveraldo. I'm sticking a set of L92's on this summer.

 

Milling a head raises a compression right? I have some ported 241 heads and milled .030 that ima use on my 5.3, soon 6.0. Freind of mind said that i should mill them more cause the 241 heads are going to lower my compression. Is that true? I see that the 5.3 heads are chambered at 61.1 and 241 heads are 66.6. My question is the lower the chamber the more compression? Or am i looking at the wrong numbers?

 

You're understanding is correct; smaller the combustion chamber, the higher the compression ratio will be. Compression ratio is a ratio of the volume of the combustion chamber, from it's largest volume (BDC) to its smallest (TDC). Say for example you measure the chamber volume at bottom dead center and it's 1000 cc, and at top dead center it's 100 cc, therefore 1000:100 reduces to 10:1. Same example but this time supposed you milled enough to reduce the CC by 10 cc, so 990:90 reduces to 11:1.

 

yea i see what ur saying on the chamber part. Like on the example, how did u get 11:1 from 990:90? Like how would u solve that?

an ls1 is 10.1
with the heads milled .030
So my combus. chamber comes down to 62, right
so how would i figure out my compression ratio???

 

There are plenty of online calculators for compression ratio, Eagle rods has one, I just googled and there are lots out there, but basically you either have to know, or measure to find out:

Bore
Stroke
Head gasket thickness (compressed and uncompressed in some cases)
Deck height (distance from piston to deck at TDC)
Piston dome or dish volume (in cc) and
combustion chamber size (also in cc).

For a fast answer though, check out this link: https://ls1tech.com/forums/advanced-...ume-vs-cr.html

Which works for you because it's discussing the LS1.

 

Alright, thanks. Good to learn a few things here and there...

 

No problem, we're all here for the same reasons!

 

Can anyone tell me if its possible to change the heads on my 03 avalanche 5.3 LQ9 to 243 LS6 Heads? I was planning on beefing up heads and cam along with intake, headers and programmer.

Is this possible successfully? ?

Any help would be appreciated

K