What kind of compression are we looking at to swap 4.8/5.3L heads on a LQ4 6.0 with stock head gaskets?

Would this increase in compression out-benefit the better flowing ports of the #317 heads?

 

Compression will go up. But the 5.3 heads dont flow near as well as the 6.0 317's. Just work some 6.0 heads. Mill them some and use some thinner FelPro .041 gaskets and you can jump CR up to 10.0-10.3 depending on how much you mill. Id say a safe mill would be .040. I only got .030 shaved off mine.

 

I'd do a 5.3L head.... I think. Are you going to have the heads worked over?

You'd open it up to mat the 4'' bore but, I wonder what the CC comes out to after this? Unmilled

Could someone post a picture of a stock 5.3L and 6.0L chamber? I'd like to see the difference.

How much does a 6.0L head cost? 5.3 heads run $200.

 

MAN YOU NEED TO GO TO E-BAY THEY ARE 5.3 HEADS FOR 100.00 AND 5.7 150.00 TE 6.0 HEADS IS WHAT COST THE BIG BUCKS

 

dang... your buddy Todd (12sec5.3) ripped me off then.

(This is a joke)

 

The heads assembled are usually 500 new. They can be found on Car-Part.com also. The 317 heads are just bigger chambered versions of Z06 heads. I dont think a super ported set of 5.3 heads could flow like the 317's. Maybe if you went with super huge valves. But Im no expert.

Oh yea, caps kill!

 

I DON'T KNOW WHAT YOU ARE TALKING ABOUT BUT I KNOW THAT THE HEADS WERE SELLING FOR 200 ABOUT A YEAR AGO TODD BOUGHT A SET FROM A FREIND OF MINE FOR 200. NOW THEY ARE SO MANY OUT THERE THAT THEY ARE NOT SO HOT ANY MORE AND I AM NOT ONE TO TRY AND MAKE A KILLING OFF OF SOME ONE.I JUST SOLD A SET ON HERE FOR 125 FOR VERY THING + SHIPPING

 

Hey Deckhand, the compression is really gonna climb with the stock 5.3L heads. There is a really good thread on CR vs volume/CC, etc, in the Internal Engine LS1/LS6 at the top of the section with a sticky note. Written by Tin Indian or something like it. Check it out for better info.
The smaller valves ( exhaust ) will not be a good trade off for the increased compression using the 5.3/4.8 heads ( both truck heads are identical, #862, so don't limit yourself ). The higher cost of the #862 castings is because the aftermarket head companies use them as cores for their Stage 1+ products ( much easier to remove material than add it with the smaller combustion chambers ).
I would decide based on application: forced induction stay with the #317 heads, high compression nitrous use modify the #862 heads.
Hope that helps, good luck!

 

Oh they dont? My worked over 5.3L heads flow 330cfm on the intake side.

 

330 at what lift??? Not too sure your heads are STOCK. Are they? Were talking stock heads here. In stock form, 5.3 heads on a 6.0 is a flat waste. CR will shoot to like 11:1 with 5.3 heads.