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[humbucker]

i have two sets of heads here, one pair with part numbers 90573744 and 90573745, and the other with part numbers 93171023 and 93171022.

ignoring camshaft differences, is there any difference in the cylinder heads themselves between, say, a x25xe, c25xe, x30xe? i wonder as i cant seem to locate the identification of the first pair of part numbers and want to be sure what engine they came from. they seem identical in every way other than the p/n.

anyone got an epc they can look up these p/n's as i had no joy finding the first two

ta 

[Marks DTM Calib]

The key difference is the size of the combustion bowl, its smaller on a 2.5/2.6 head.

There should be some engraving on a small flat section on the inlet side, cambelt end (might be covered in muck!)

[humbucker]

engraving on the corner of the head says 30LT 4641 on on and 30RT 4633 on the other.

does this suggest they're 3.0 heads? and if so can they be fitted to a 2.5?

[humbucker]

anyone got further thoughts on this?

[Marks DTM Calib]

engraving on the corner of the head says 30LT 4641 on on and 30RT 4633 on the other.

does this suggest they're 3.0 heads? and if so can they be fitted to a 2.5?

Yes, they are 3.0 heads (R being Right side and L being left side).

If you fit them to a 2.5 then you will lower the compression ratio.....and you dont want to do that 

[humbucker]

at the risk of sounding like a total philestine what are the implications of lowering the compression ratio by putting 3.0 heads on a 2.5 block?

[Marks DTM Calib]

at the risk of sounding like a total philestine what are the implications of lowering the compression ratio by putting 3.0 heads on a 2.5 block?

Lower power and economy.....in theory

[humbucker]

other than lower power would there be any issues re reliability i.e. potential destruction of engine?! i mean, is the application of these heads, and the advice against it, purely a performance related issue?

[humbucker]

and can a 2.5 head gasket kit be used on 3.0 heads on a 2.5 block?!