[Mikael Nielsen]

Hello everyone.

I hope someone can help me to understand the different heads you can get on the 400 engine.

It all started with I bought a Trans Am from 1979, with a 400 block from 1973. Previously owner could not get it running due to low combustion pressure (40psi), so now it's my turn 😅.
He says I just need to swap the heads to the original ones that I also got with the car and buy new valves.
So I have two different heads, but I don't know which ones to mount, and with what valves/valves springes.

The heads mounted now has the stamps:
6X GM7

The other heads have two different stamps on each head:
6X GM2 and 60 gm4

The 6X GM7 has single springs mounted, but I don't know if the is correct?

I hope someone has some kind of knowledge they would like to share, as I am quite confused.

Regards Mikael