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MG MGB Technical - Swapping Cylinder Heads

A pal of mine (who I will eventually lure into the vicinity of a computer) has been offered a replacement cylinder head with hardened exhaust valve seats (which his own head hath not).

He wonders whether it will be compatible. His GT has a 1966 18GB engine - one of the first 5-bearing units - and the offered head is a 1971 model. It doesn't come with rockers, shaft and pedestals, so he will be hoping to use his original set.

Will this combination work?
Nick

Nick, the casting number(s) will help members help you!
Art Pearse

Sorry - can't get hold of him right now. I'd hoped somebody here would have general knowledge of engine history, or would have swapped blocks and heads like this.
Nick

Yes this head will physically fit but if it is an original from an 18V engine it will have large inlet valves which will foul the top of the cylinder block. This can be alleviated by grinding a cut out at the top of each cylinder adjacent to the valve position the dimensions of which can easily be found on line. In addition please make sure that the rocker oil feed lines up between the rocker pedestal and the head otherwise the pedestal will have to be changed for the correct one. If it is an original 18V head it will have the casting number 12H 2709 cast below the rocker cover if not original it will have a different number and will not have the larger inlet valves so will not need cut outs on the block
Iain MacKintosh

The inlet valves will not hit the block. The problem with fitting 18v heads or heavily skimmed pre 18v heads is ex valves hitting block. The 18v had factory eyebrow cutouts which can be hand filed with a half round file in earlier blocks.


Peter
Peter Burgess Tuning

Thank you very much, Iain and Peter. This is just what he needs to know. Watch this space.
Nick

He's back. And he's gone and bought it.

It's a 12H 2595. Does that sound right for a big-valve head?
Nick

Austin 1800 head
Google 12H2595 there is inf
Art Pearse

1800S head similar to 12H2709 but 9.5mm deep chamber as opposed to 10mm deep chamber of 2709. Some castings have dual stamping 2595 and 2709. Nice rare head if crack free.

Peter
Peter Burgess Tuning

This thread was discussed between 12/06/2012 and 15/06/2012

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