Had the head off and got it converted to unleaded. Also new valve guides and a good clean up.

Notice it has a combustion chamber machined in (its a 691 block, not a 711). I see from XFlow book not good ! Engine came out of a 1600GT Capri.

Can I replace 1600 pistons with 1300 and get the compression up again ?

Shame you had the head converted first-flat heads are much better. You should get better compression using 1300 pistons though they may need machining if your using a hot cam.

HTH

1300cc or even 1100cc pitsons would work well. There were a couple of sets on ebay recently, good place to get them farily cheap.

mark

Thanks.

No I haven't a "wild" cam in just the GT one it came with. Was thinking of a fast road cam when I lift whole engine out over winter.

1300 pistons will do you fine, even with using fast road cam.

The early shallow chambered X'Flow heads weren't that bad, and compression was catered for by the piston being different to later flat head crossflow - no valve cutouts. I used to use one of these heads to good effect with 1600 flat topped Lotus pistons in a 1300 block. Don't worry about it, it will be fine!