SpeedFreak350

I'm going to be picking up an 5.7 LS1 engine. Question is, how do you differentiate between the LS engine varieties? Don't they all look alike? I don't want to end up with a 4.3 or 5.3... Any markings to look for? I know I could take the seller's word for it, but I have trust issues Thanks!

NVR_SPDS

iTrader: (39)

Back passenger side of the block says displacement. You should also be able to use the casting number just below the drivers side head, on the back of the block. Check head casting numbers too.

Always2Slow

iTrader: (8)

Just make sure its aluminum. Only the LS motors are aluminum and truck motors are cast iron.

NC98Z

iTrader: (1)

4.3 is a six cylinder and a 5.3 has a cast iron block.

Anniversary "Z"

iTrader: (26)

^^ what he said, kinda hard to pass these blocks off for something they are not since GM stamped "5.3, 5.7, or 6.0" into the mold these blocks came from

SpeedFreak350

Cool, thanks everyone! I'm searching for the casting #s right now.

Mighty Whitey

The only instance you need to worry about the casting # to identify displacement is when purchasing a cast iron 5.3, they share the same block as a 4.8. Other than that, all the displacement numbers are cast in the block

BStowers023

iTrader: (1)

853 and 241 are stock casting LS1 head numbers.

NVR_SPDS

iTrader: (39)

Heres a reference for casting numbers:
http://chevythunder.com/LS1%20components.htm