1-21-71 Day time build, GM 340p 35870020

[Kram1976]

So I think it's a 1972 engine. My question is if the "P" is for premium gas what was the original compression ratio. 10.25:1 or the lower 8.5:1

 

[crackedback]

71 model year engine. The "G" in that string tells you model year. yes the "P" is premium fuel.

3587 = May 24 1971 so it's a later in the year 1971 model, probably real close to end of 1971 production .

There should be numbers on the pass side pan rail, close to a drain plug. Should have the year digit, factory and last 6 of vin to help tell you.