11 replies to this topic

[marsy]

I asked this a while back, but have now cleaned the head up and noted numbers by thermostat which are 12G 1805 what does that mean? 

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[marsy]

Oh noted its got double valve springs too.

[Tupers]

MK1 Cooper S head. 

[A-Cell]

Casting is probably 12G940, if the valve sizes are 35mm inlet and 29mm exhaust and it has 11 stud holes then it is a 1275 Cooper S head.

[marsy]

Yup casting is 12G940 mowog I measured the valve sizes roughly and they seem to be 30mm and 35mm, so could be 29 and 35? As used a tape measure so not accurate.

Which holes do i count to see if it's 11 stud head? Thanks 

[Dan]

  It is, you can see on the photo.

[mini13]

late cooper S head, has the cooper S rockers too,

 

looks like it may have been ported a bit too.

[marsy]

Cool, so what sort of extra performance would you get from this head, compared to standard? 

[Cooperman]

If you get the compression ratio correct at about 10:1 you could gain a few bhp. Of course, you will also need to improve the carburation and exhaust system if you haven't already done so.

[marsy]

If you get the compression ratio correct at about 10:1 you could gain a few bhp. Of course, you will also need to improve the carburation and exhaust system if you haven't already done so.

 

Compression ratio? How's that done then? (Sorry) 

And have twin carbs, and looking at getting a straight through rc40 exhaust

[marsy]

Would this head go straight onto an ordinary 1275 block? Or is there modifications needed? 

[Cooperman]

It depends on what the compression ratio would be. There are so many different types of piston used over the years that measurement & calculation are vital. It's no good fitting a better head if you end up with, say, 8:1 compression ratio as it will simply just be slower.
The basic advice is to understand what you are trying to do and why before starting to do it.
The Cooper 'S' head is also drilled to take 11-studs, whilst the basic 1275 block is drilled for only 9.