Cylinder Heads - what fits what

[NickA]

Just musing after seeinga new bareMk1 head on eBay, can you fit a Mk1 headto a block with Mk2 (domed) pistons or is it the other way e.g. a Mk2 head will fit a Mk1 with flat pistons?

Anyone mixed heads? I sure I read someone had at sometime without any detrimental effects

[redstag]

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Hi Nick,

I think the issue would be a mk1 head on a mk2 engine raises the compression ratio too high. I believe the mk2 head on a mk1 engine is ok though.

Pete

[loudnproud]

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Hi Nick supprised nobody has said this before but don't mix heads on an engine use a matched pair either Mk1 or Mk2 otherwise you are likley to end up with a poor running engine. Peter

[dougie]

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Is there a difference between the mk1 and mk2. I have both here and cannot see any. all have the LM25 cast into them.
dougie

[NickA]

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dougie wrote:

Is there a difference between the mk1 and mk2. I have both here and cannot see any. all have the LM25 cast into them.
dougie

They have different numbers cast into the head, mk1's have 307872/3 V3142/3
and Mk2's88313210/11 V3293/4. The shape of the combustion chamber is also different.

[DJT]

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NickA wrote:

dougie wrote:

Is there a difference between the mk1 and mk2. I have both here and cannot see any. all have the LM25 cast into them.
dougie

They have different numbers cast into the head, mk1's have 307872/3 V3142/3
and Mk2's88313210/11 V3293/4. The shape of the combustion chamber is also different.

Later cast Mk1 heads can also have the part numbers preceded by '88' as well, i.e. 88307872/3. This was the case with an unused Mk1 LH head I bought a couple of years ago. The adoption of the 88 was a rationalisation programme within BL, apparently.

Dave