O.k. Im a (traditional) Pontiac guy who just purchased an '87 T/A. The car's VIN says its a 305 from the factory but the previous owner claims to have "run the numbers on the block and its a 350". The purchase price was dirt cheap so Im not losing anything either way but I want to know if its the original 305 or if a 350 has been swapped in at some point. How do I tell on a Chevy? Pontiac makes it easy on us and just stamps it on the block.

 

check the block numbers and head casting numbers, then go to Mortec.com to see if its a 350 or not.

 

Chevy does too.
Check the back of the block, right where the tranny bolts up to it. Drivers side.

 

Casting # on the block....

Conveniently located in the most conspicuous place on the block, right out in the open: on top of the bell housing flange behind the driver's side head. </sarcasm>

You may also find either 5.0LG or 5.7LG cast there, if it's a later block; which makes it either a 5.0 (305) or a ..... I'll let you guess what. The last 3 digits of the casting # are also on the side of the block in various places, often visible from underneath.

 

there is also a pad on the block infront of the passenger side cylinder head you can use to figure out what it is. i think all blocks have a number cast there but not sure. i know my 89 has it there as well as behind the drivers side head

 

its on the left side of the block on the back where the trans bolts to it ,will have 5.0 or 5.7 in raised numbers.hard to see in the car. there are raised numbers on the right side same place.theres also numbers stamped on the block in front of passenger side head these may be easier to get to but not as much info last 3 numbers are the suffix code.go on google and put in chevy engine block numbers should find a site to tell what they mean. hope this helps,later jimmy

 

Cool. I dont actually even have the car here in front of me yet. Its still about two hours away. I just wanted to know, I did'nt think Chevy made it that easy on you. Thanks...even if one or so of the answers was filled with a little more sarcasm than necessary.

 

Stamped, not cast, and all but useless even when not obliterated by rust, time, and/or rebuilding as they almost invariably are.