I need help identifying an Olds block. I thought at first it was a 72 350 because it had 7A heads. (I had forgotten about the later 7A heads that had the "A" in a different position) The EGR valve also gave it away as not being a 72. The numbers behind the water pump really confused me but they are probably wrong anyway. I did my best to scoop away the grime but this is the number I got: 4790GM5-OLG...? upon researching the closest number I found was 554990 which was a '77 403. Any ideas?

 

Im thinking its a 307. On the side of the block below the center freeze plug, it should say what size the engine is. If it is a 307 it will say 5L, it will have the cubic inches for a 350 and 403. Where did this engine come from?

 

look above the water pump next to the oil fill tube. That's the casting number you're looking for.
If that's where you found it, more research needs to be done.

 

I got the number from that area, but there was so much crud and the guy who was selling it didn't have a flashlight. I think some of the numbers are right but not all. The side of the block would have been even harder to see.
It was in a Cutlass G body. but the guy said it was not original.

 

That's an 86-90 roller cam 307 block. Sorry.