6 replies to this topic

[croc7]

Am I able to use a 12G940, 11 stud Cooper S head on a 1275 block that hasn't been drilled for the additional two fasteners?

[nicklouse]

You should. There are no holes in the block that could cause problems.

But I have seen one leak out of the thermostat side but that may have been a gasket issue.

[croc7]

It’s my understanding that the two fasteners were to help with the higher compression of the original S engine but if I’m already higher at 10.5:1 using a 9 stud head I think it should be fine. I haven’t been able to find a flow comparison test between the S head and a more contemporary performance cylinder head.

[Rorf]

Why not drill and tap the two additional holes, easier enough. Ensure you use a good quality head gasket and do not over torque the nuts and two bolts.

[Spider]

You should be able to do this fit up without issue.

[nicklouse]

It’s my understanding that the two fasteners were to help with the higher compression of the original S engine but if I’m already higher at 10.5:1 using a 9 stud head I think it should be fine. I haven’t been able to find a flow comparison test between the S head and a more contemporary performance cylinder head.

You will not as every head is different. It depends on who did it. If you want to know you will have to have the two heads tested back to back.

As to if the two extra fasteners do anything useful is open to debate.

[Turbo Phil]

Absolutely no problem using an 11stud head on a 9 stud block.
A well modified head should outflow a standard S head by an absolute mile.

Phil.