6 replies to this topic

[Spherix]

Hello,

I've been searching the net for a while but cannot find a defnitive answer. I've been told the head on a mainstream cooper engine would be the same as the MG Metro (not to be confused with the Austin Metro version). Is this correct? I've been offered a Longman cylinder head with 35.7mm inlet and 29mm exhaust valves and I want to know if that would actually be worthy of purchasing, or wether I end up with a 'new' equal cylinder head.

Thanks!

[Tommyboy12]

Standard valve sizes by the sound of it but is likely to have some porting as its from a specialist. Will give it a boost over a standard head.

[jbj]

The mainstream cooper does have the same engine as the later unleaded MG metro but neither have the big valve head that was on the earlier leaded metros. The std valve size is 33mm inlet 29mm exhaust.

[Cooperman]

The standard inlet valve size for the 1275 Cooper was 33.5 mm. However, the Haynes manual says it is 35.6 mm. which is the MG Metro size.

[Spherix]

Thanks for the replies, although it's the same information (and still contradicting) as I've found before.

The head I'm being offered is indeed ported, but -what if- the valves are the same as my current head? Would the porting that has been done improve power by any significance? The current head that's on does it's job fine, so spending a few hundred bucks on a same head that is ported and fitted with double valve springs in opposite to what I have now would have to be worth it. I've tried looking it up in Vizard's book, but the cylinder head chapter is quite a book itself

If anyone knows for sure what the valves on the mainstream cooper head are that'd be great info.

[jaydee]

Inlets 33.33mm exhausts 29.2mm
The mainstream cooper has just a standard late 940 head and it was the RSP that was fitted with the UNLEADED MG metro engine (smaller valves than the leaded one).

Check the engine numbers and cyl head numbers, then give a look at the blog at calver st, there should be a section with all the valves sizes related to cylinder head and engine.

[ace01]

Regardless of the size of the valves in the standard item, a Longman head (if genuine) will offer a good increase over standard. The porting is probably more important than the size of the valves on their own.