seeyaa

what would this do to performance. how much do you think it would bump up compression.do you think this would be a good combo with a nice cam tr224 or something like that.

Nikon02

i always thought the 4.8 and5.3 were the same motor just with a diffrent stroke?

seeyaa

i think the 4.8 has flat top pistons

Nikon02

The bussiness side of me would say no because it would be cheaper to mass produce one type of pistons then two diffrent types in the same size.

But the truck guy in me dosnt know for sure.

seeyaa

i thought i read that some where on here but maybe i miss understood or misread it.

Nikon02

i ddont know someone will tell us both before long.

Yelo

AFAI the only LSx motors with flat-tops is the LQ9 6.0 liter and the early LQ4 6.0 liter (but it seems the LQ4 is on a per-motor basis....some like myself and Jerry2500 have them, others do not)

Tractionless

Actually the 4.8L piston is a flat top, and the 5.3L is dished.

Reason: they both use the same head, but the 5.3 engines have a longer stroke than the 4.8L, so the 5.3L with the longer stroke would have had too much compression with a flat top piston.

Don't know how much the compression will increase using the 4.8's piston heads on a 5.3 though. , but I know this:

-----5.3----------------------4.8------
bore X stroke-------------bore X stroke
3.779" x 3.622"-----------3.779" x 3.268"

Hopefully someone with a compression formula can use this.

Snake Eater

Your right on.

Yelo

Assuming:
7.5cc dish (5.3 piston....assuming it's the same as the 6.0 piston dish)
61cc chambers
.060" gasket (3.95" gasket bore)
9.5:1 CR

Calculating quickly it should be around 10.35:1 after the 4.8l piston swap.....