Port size for a 2.5 cis engine, 964 cams 86mm je

[Mexicoearly911]

Hello everybody let me present you with my new acquisition, is a little neglected 1977s with a 1973 2.4 cis engine, I had a set of 86mm je pistons 9.7:1 cr with biral cylinders than i was going to use for an other project and i got a set of 964 cams to make a 2.5 liters engine, the question is the port size, the stock size is I 30, E 33 which seems to small for this upgrade, I ask the advice of the engine and cis experts to advice me on this matter. I would like to get arround 180 hp out of this engine



Thanks

[Mexicoearly911]

Of couse I will use the cis installed on the engine

Advise is very apreciated

Thanks

[crummasel]

Hi there,
its quite likely that domed pistons will not make you happy for a CIS application since CIS needs bowled pistons to generate a reasonable swirl which it needs to create a good inner gas/air resolution.
964 cams seem to be OK (as long as its a grind on a small diameter 3- bearing cam core), but you should see to get you a good set of bowled piston/cylinder set.
Greets,
Robert