Ok I was looking at the H-production head as Nismo calls it and noticed a hole plugged that wasn't plugged on the GX head. The hole is on the manifold side in between #2 and # 3 combustion chambers. It is about 3 mm in diameter looks like an oil gallery. If I bolt the H-prod head on the GX block do you need top drill out this hole??? can the whole be drilled???

Tom

I believe this hole is for coolant through the intake manifold. All the stock GX (SU) intake manifolds had water/coolant circulating through the intake. I guess it's supposed to help regulate temps, but I always thought it would heat the intake up too much. You should be able to tap and plug this hole. Pictures would help give a positive identification of what this hole exactly is though.

A12 GX Head

This one only has the intake water holes under two of the intake ports:


469

Or do you mean it is on the combustion face? There's as small one here between 2 and 3:



1234

Here's the matching hole on the A12 block:



502

I do indeed mean the face. Duuhh should have mentuioned this. After looking at it last night it appears to be a cooling passage. Question still is does this need to be drilled out to match the deck on the GX block???


Tom

Can you post a picture of your cyl. head showing the passageway you are referring to?

Not sure if this will help, but check out Info required re A12 Gx Head