8 replies to this topic

[jmmini]

I've been setting the tappet gaps today, the first time I've been in the head. It says "12G940" I think it reads and it has a smaller spring inside the main spring on the valves. I've got pictures but are too big to attach.

Is it a good head or a standard one?

[jmmini]

I've tried looking it up but there seems to be many variants. I'll sort out a photobucket picture later on

[Skortchio]

Boggo standard for a 1275 and quite fancy on a 998. Someone has fitted double valve springs to it, which if you don't have a lairy cam are sapping power and wearing your internals slightly quicker than necessary. Other than that, there's little can be deciphered from the outside unless it has a stamp on it from an engine building, slark for example. It might be a larger inlet variety, but I'm not aware of anyway to tell that with it fitted.

Edited by Skortchio, 06 April 2013 - 04:37 PM.

[jmmini]

It did have other markings on it, non that I cared to take a picture of, one had the letters I think it was '90*' or '*90' I just know it had a 9 abs an 0 in it. And some over to the left which had a few more letters but I couldnt see them very well. The car dies feel really fast compared to other 1.2-1.3 L cars I've been in

[Cooperman]

All 1275 heads are based on the 12G940 casting, except for the early Cooper 'S'.
There are several things you need to do to establish what you have:

1. Measure the valve head diameters, inlet & exhaust. Standard for most 1275 Minis is 33.5 mm inlet and 29.5 mm exhaust.
2. Examine the inlet & exhaust tracts to see if the valve guide bosses have been removed. Also examine the combustion chambers to see if they have been re-shaped by comparing with photos of standard heads.
3. Measure (accurately) the volume of the combustion chambers. Standard is 21.4 cc. Then measure the piston dish and measure how far down the bores the piston tops are at TDC. This will enable the compression ratio to be calculated.

Only then will you know what the head specification is.

[jmmini]

One of the markings says 268

[Cooperman]

One of the markings says 268

You can't tell anything for sure about older 12G940 heads without doing the measurements and inspection.
So many have been gas-flowed, skimmed, modified or otherwise 'b******d about with'.

[jmmini]

I'll have to get a head gasket ordered and whip the head off then! It's like digging for treasure lol

[KernowCooper]

Get a Payen Gasket it will save you trouble a while down the road.