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What's needed to upgrade 1974 base 911 to S specification?


Model: 911, Year:1974, Mileage:80,000, Type of use:Street use only
Im in the process of rebuilding the engine on my 1974 911. Unfortunately I have Alusil cylinders and I cant locate 90 mm CIS piston and cylinders for the base model, (8.0:1 CR). However replacements for the CIS S (8.5:1 CR) are readily available.This seems like a good opportunity to gain some additional horsepower. My plan is to upgrade the engine to S specifications. That would include porting the heads and intake manifolds from 32 mm to 35 mm, porting the exhaust from 33 mm to 35 mm and moving to a S camshaft. I also plan on adding an external oil cooler to keep the heat down.The CIS injection system was working fine, and Id like to retain it to keep my rebuild costs down. Is the K-Jetronic system the same on the base 1974 911 and the S or will that need modification as well? Ive also read where people are using modified 964 camshafts with CIS, would that (or some other cam) be a better option than the S camshaft?Thanks for your advice,Peter

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