- Wed Jan 19, 2022 3:14 pm
i guess part numbers of heads are not that important as they are NLA , so its just the numbers cast into the actual head that we need to know about.
i asked the question on here as a guy contacted me to see if i had a spare good head as his was badly corroded, and i just needed to know what the first head casting number was when Porsche raised the bosses of the head bolt mounts to stop possible cracking.
the guy who contacted me posted a head cancer thread on RL and Mr B gave the answer below, for 87-95 models ONLY:
1R and 2R heads are from 1987 and 1988 engines. They are prone to cracking at the base of the lower head washers. Avoid them, like the plague.
In 1989, Porsche raised the bosses. in the heads, to prevent this from occurring. These heads were 3R and required longer head bolts than the 1R and 2R heads.
Porsche made a few more changes, over the next few years (nothing extremely important, for your use), and 4R and 5R heads appeared on engines.
You can use any head from 3R and later.
so now we know.
i should have taken the time to check the 5R head i sold him to see if i could spot any of the changes between the 3R heads i still have, but i did not, the head was in lovely condition though
hope this helps someone
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90 GT orange
88 SE silver
87 S4 auto Diamond blue
88 SE red - now Roger's