scothron3

when you have the 4.8/5.3 block and casting number 12551358. from there how do you identify what size your running the 4.8 or 5.3 i know the blocks are the same but different stroke but do they have a number to show the size it is? thanks!

1quickirocz

on the rear of the block where it says "4.8/5.3" there will usually be a paint mark on or right above which ever one it is. If not try to look at the pistons. the 5.3 will have a dished piston and the 4.8 will be flat top pistons.

A. Slone

^^ thats not entirely true.. i have a 5.3 with stock flat tops in it. if you have the heads off to see the pistons, you should just measure the stroke.

1quickirocz

what year 5.3 and iron or aluminum block on yours?

scothron3

it was out of a doner truck that was parted out im not 100% sure but 2003 0r 2004. its an iron block, my head casting numbers are 862, i have a 4.8 in my company truck witch have the same heads witch is making me feel its a 4.8. i did tear into the engine and i have the dished pistons with the plus sign looking marking on top. but then again some say that dosent matter, if i measure the stroke, what size should i have, the 5.3 should be longer than the 4.8 right? thanks again!

scothron3

checked my crank and found the casting numbers of 12552216 witch i found is the 5.3 crank, the 4.8 has a c/n of 12553482, so that answeres me question!
just weird the same heads are used.....

chrisfrost

iTrader: (8)

Yes it's weird alright ,,,,,,I can't believe GM not only made it hard to know which size but also those blocks were used for 5 or 6 years or more so the only way to know which year it is is to get #'s from almost every part in the engine and the PCM and look on here and Google ,,,,,,,,,blah blah ,,,,,pita

scothron3

yeah that is kinda shity, i wonder how many people bought a so called (5.3) thats really a 4.8 i kow i thought i did! haha that is kinda screwed up but im really in the market now for a 6.0 to get some responce out of my truck build!

chrisfrost

iTrader: (8)

I bought a what I was told was a 5.3L that turned out to be a 4.8L so the guy I bought it from gave Me a 5.3L and let Me keep the 4.8L so I've got some extra parts. So I spent alot of time porting a set of 706's then after just about finishing Them I find out there have been problems with many of the 706's leaking coolant so the other set I have are the 862's so I'm in the middle of porting those and that's ok because I've learned alot working on the others and learned more from LS1 Tech so the 862's will be quite a bit better .