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fitting a rebuilt 12g 202(off a clubby 1100 -not a 997 cooper) head to a 1965 std 998.. and using a single hs4 carb and manifold rather than the 1456 head and hs2 carb currently fitted

also have a brand new std 1275 gt exhaust i can lob on for good measure.....

i find it gutless with the hs2,although the std early 850/998 head is in good order and has 155 psi compressions

im wanting a bit more torque and hoping my idea will smnooth the engine out a bit..

or should i just leave it alone?

You'll need to get the CR up as it will lower a bit by just fitting the 202, the combustion chambers are bigger on the 202. It will improve the performance, but don't expect heaps. Since you maybe having the head decked, get the CR up as high as you can for the fuel that is available to you. With a stock cam profile, think of a CR around 10:1 to 10.2:1 for 98 RON fuels. If you've a more radical cam profile, go higher on the CR.

I'd also suggest going for header and exhaust system for a small bore engine, you'll find it'll improve the low RPM torque, small engines like small pipes.