1275 Head onto 1100 Block

[Kiwi Craig]

I am asking for a friend who has an A40 Farina.
Are there any issues fitting a 1275 head onto his 1100 block?
He is mainly concerned about valve clearance, but also any other problems.

[bwaminispeed]

If the head hasn't been skimmed, and, assuming standard cam and rockers, you can usually get away without pocketing the block.......

Do lots of measuring, and, use the 1275 head gasket......

[Dearg1275]

I would dry build the head on the block without pistons and look up the bores. Wiggle the head to all possible locations (there’s a fair bit of latitude) and make sure however the head gets dropped on that the valves clear. A dab of engineers blue on the block walls might help spot any slight contacts you might not feel. Use rocker spacers spring instead of valve springs to make it easy to press the valves up and down with your fingers. You will feel any contact better that way.

D

[Costafortune]

It's a slightly rubbish conversion as the 1275 chambers are so much bigger you end up with a low CR unless you skim the head so that the valves almost touch the block. Then the siamesed 1100 bores don't really match up with the equally spaced 1275 chambers. It's okayish but.....
A decent 12G295 head was made for the 1098 engine and they're still not mega expensive at 2-300 quid.

[bwaminispeed]

The 12G295 head has the largest combustion chamber of all, at 28cc........1275 head is 21.4cc.......

So, compression wise, the 1275 head is best.....

[Spider]

Check the Oil Feed hole too, as this is in a slightly different location between small and big bore engines.

It's a slightly rubbish conversion as the 1275 chambers are so much bigger you end up with a low CR unless you skim the head so that the valves almost touch the block. Then the siamesed 1100 bores don't really match up with the equally spaced 1275 chambers. It's okayish but.....
A decent 12G295 head was made for the 1098 engine and they're still not mega expensive at 2-300 quid.

It's not a conversion I've tried, but, CR aside, I gotta agree here as there's a lot of valve shrouding.

[Costafortune]

The 12G295 head has the largest combustion chamber of all, at 28cc........1275 head is 21.4cc.......

So, compression wise, the 1275 head is best.....

I guess it's bigger and thus more shallow.

That would then make the CR very high however.