Hi. I am looking for my oldsmobile cutlass 1974 engine serial number to check it the number maches the lisance. On the front above the water . pump there's a casting number 557265 4B. So iguess the engine was replaced by one of the previous owners to a 1978 403. Befor i 'll rebuild it i want to know that it is legit.
I' d also like to know if theres a thred on this forum for improving preformance for that low compression engine

 

That casting number could have been used on any 1977-1979 403 block. The VIN derivative stamp will tell you the exact year of the block. The second character is the model year (7=1977, 8=1978, etc). This engine has been swapped, so I don't know what you are looking for, exactly. Nothing on the motor will match anything on the car from a VIN or licensing standpoint.

 

 

That's the only place. Keep looking. Try a pencil rubbing. It can be difficult to read faintly stamped numbers with the block in the car.

 

It could also be a warranty replacement block (for the donor vehicle that it was swapped out of) that the mechanic got lazy with and didn't re-stamp. I had a 350 like that in a 76 Salon that I owned many moons ago.