5.3 vs 4.8 difference.....and what is the goo on piston?

[brian617]

4.8 FLAT TOP, 5.3 DISH

RUSTY WATER?

[53dawLsSwap]

oh, that could be! I didn't think of the rusty water...wonder if I should try sucking that out, or if maybe the head gasket is bad? Hmmm

[Fast355]

4.8 FLAT TOP, 5.3 DISH

RUSTY WATER?

Not necessarily!

I have found engines swapped in place of others many times. These trucks are 20 years old now.

[In-Tech]

~2006 and up 5.3 are flat top pistons. It's a good way to tell at a glance in the junkyard though.