[muscle_collector]

around 1981 or 82 i bought an engine out of a guys gasser rod. it was one of the hardest thumping pontiacs i had ever heard. he said it had 12.5:1 compression and was hilbourn fuel injected. i stuck it back and it just got buried over the years. the other day a friend noticed it and got real interested in it so we cleared out around it and started looking at it. my question is on the heads it has the casting 536109 and on the flat areas above this on one side has an X and the other side has an O and what appears to be an E down lower and to the side. anyone know what they originally came on?

[Sirrotica]

Here is a link to John Wallace's head ID chart for the 1960 536109 heads, it even talks about the X and O markings for cc volume/compression ratio, and HD springs:

http://www.wallaceracing.com/cgi-bin/head.cgi

[muscle_collector]

thanks for the info. it looks like it was a 10:75 compression with heavy springs. i had one guy tell me they are the 425A heads. any thoughts? another thing i saw on that chart was on the 58 heads it said with xx it was fuel injection. one of the heads appears to have the x and the o double stamped.

[tom s]

I think in 1960 it was called a 420A block,same site might confirm

[Stuart]

They were 425A heads in 1960, 420 heads were 1959. Assuming it's the correct 425A engine block it has four bolt mains, look for block codes F1, F4, M4 or C1.

[muscle_collector]

any ideas on the E stamped on them?

[Stuart]

I don't know what the E may mean. I didn't find any mention of it in Pete McCarthy's book and I know there wasn't any E stamped on the heads on the 425A in my '61.