Hey all,

I could use some help identifying 2 heads that I've recently acquired. They both seem to be the same casting, only 1 has had a substantial amount of work done to it and the other seems to be a virgin head. My first thought is that they could both be H10 heads, let me know what you think.

What I know about the worked head:

- A12 Head
- Ex Formula 3 last used in 1990
- Ran with 76.85mm pistons at 1298cc
- 12.5:1 compression, milled to 72mm thick
- Brass valve guides
- L16 Valves machined down
- Intake valve = 38.8mm
- Exhaust valve = 31.65mm
- Intake port = 32mm






















Other head:

H10 head says "JAPAN" on the top side, so I'm not sure what you've got. Can you post pics of the spark side, port side and of the front and rear faces? What size are the valves in it?

May be an A10 head?

The valves/ports have already been enlarged so I can't use those to identify the head. The sizes have already been listed above. Here's some more pics:

Sorry, I should have said photos of the "other" head. It is round port too?

After checking, it seems the H10 heads had no casting words (GX had "NISSAN" and "JAPAN"). Everything else points to an H10 (or maybe an earlier head)

Your "worked" head is unusual in that it is missing a vent hole

Attach file:

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  missing vent hole.jpg (74.54 KB)

Here are some more pics of the other head. I found it quite strange that I got both of these heads at different times and from different people, yet they seem to be the same indecipherable casting.

I also noticed the missing vent hole. I thought it must have been plugged at some stage for some reason.