hey everyone just have a question. i recently bought a car that had heads "done" to stage 1 specs. but upon looking at them i found the number 1231786 with a number 3 above it. now the area by the valves has a cut out for the larger valves and is not a straight cut...also on the other side i found j/25 under the gm stamp..any help in id' ing these would be great. thanks in advance john
Stage-1 valves have the same part # as regular heads for a given year. You need to measure your valves. Stage-1 intake and exhaust valves almost touch in the middle. The 3 is a production # and the J25 is the date code=September 25
Stage one used same casting number as regular heads, just bigger valves. I think that is a 70 casting number.
1231786 is a 70 head. From what you describe, they are stage 1. Measure the intake valve to be certain. Stage 1 intakes are 2.12 inches, regular are 2,00 inches.