86 g-body

iTrader: (3)

How can u tell them apart ????

Pocket

iTrader: (22)

Drop the pan and check the crank casting number

For GEN III LSx engines, the 4.8 has flat top pistons and the 5.3 dished. If you dont have a boroscope this is a difficult task

If the whole truck is still there, check the VIN

stoopid john

I went through the same thing, the guy said 5.3, but it was on the ground and no other way to tell.

It ended up being a 4.8, you just can't trust people.

Pocket

iTrader: (22)

Roll it over

rtr2001ss

iTrader: (2)

5.3L = 3.622" Stroke, 4.8L = 3.267" Stroke. If you can measure that you'll be good to go.

three83'camaro

yeah only way i know is to look at the pistons, looking for flat tops in the 4.8

neal64ss

iTrader: (1)

If the engine is out of the truck and you can get a light and just the right angle you can tell if it is a flat piston or dished by looking in the spark plug hole. It isn't easy but can be done. Other than that you have to pull the oil pan or the heads.

Pocket

iTrader: (22)

Flat top vs dish only applies to GEN III. GEN IV 4.8/5.3 both had flat tops, only the crank and rods changed. Do yourself a favor and check the crank casting number to be sure

Jimbo1367

Is there any block, head, crank casting number book out yet?

95silverstallion

dont the blocks have the liters cast right into them on the backside just below the deck surface?

Pocket

iTrader: (22)

Both are the same bore block so GM reused it for both

You'll find 4.8/5.3 cast into the front and rear so thats no help. Cyl heads were also the same for both, only the crank, rods and pistons changed

MJs1FastSS

iTrader: (149)

castings are the only way /internal if accessable