The 4.8/5.3 block can be bored to the 3.898(5.7) bore and use 5.7 pistons of course. 5.7,5.3 & 6.0 pistons all share the same wrist pin height in the piston due having the same stroke crank and same length rod. The 4.8/5.3 heads will add compression over using 5.7 heads.

 

my number 1 &3 have oil on the spark plug threads when i pulled them out. would this be rings or valve seals? this is why i wanted to know. i need a cheap way to get a good motor in my truck if its the rings. although those two pistons did hit a 265-270 on a compression test. all the others hit 195-200.

 

The extra oil in the cyl could help the rings seal and give better pressure on a compression test. Most likely it is just valve seals/guides. A second ring busted could show good on a comp test but have blow by and burn oil. If you don't have excessive blow-by, smoking or high oil consumption I wouldn't worry about it. If it isn't fouling the plugs then i'd be in no hurry of replacing the motor.

 

it does use a little oil but as per gm its "normal" for this one i guess. about a quart or alittle more every oil change. is there a way to check the vave seals?

 

If it puffs smoke out the pipes when you first crank it in the morning then that is a sign of leaking valve seals. That is pretty much the only way to tell short of tearing it down.

 

The 4.8 and 5.3 pistons have the same pin height and should interchange for a cr gain. The shorter stroke is made up in the longer rod.

Kurt

 

your right, I stand corrected.

 

thats what i thought but didn't want to argue lol. is there some where to look up the specs and make damn sure of this or is it just in the math that with the longer rod short crank and same deck height that this should work?

 

i'll check that i think it does. last truck i had was a s-10 with a 4.3l and they were known for that so i never thought to pay any attention to this one.