Air Pump Stud Replacement - '81 911SC

[ROW911SC]

So I've removed the air pump and bracket and now need to replace the existing studs with the shorter 8x42s. I plan to use the "two nut" method to back out the existing stud, but when I lay the replacement alongside seems like it will have to sink pretty deep. Am I missing something? Thanks.

[Targalid]

That looks about right. I just took mine out and replaced them with 40 mm bolts. The bottom one has no structural function but the top two are required to keep the chain case from leaking.

[ROW911SC]

Thanks. You wouldn't happen to know the torque spec?

[Ian Comerford]

I used a die nut to extend the threads on the existing studs down to level with the crankcase plate and then cut the studs down to the same length as other ones. This avoided the risk of breaking a stud whilst removing the three. One washer and a lock nut on each one finished the job.

Ian

[euro911sc]

That looks a little long to me. I also think you have it backwards. The short end will screw in all the way to the flat and the long end will be exposed. I bought new studs to do this on my SC, but forget the lengths...

Keep in mind that the descriptions of studs are not the lengths, but the thread lengths. I posted on this in the engine forum a few years ago... I'll see if I can find the post. So you need to do some math to get the right length stud from the dealer/pelican.

[euro911sc]

Interesting note on case studs

Here is the link to understanding how stud lengths are specified.

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After re-reading the above thread I know you have the stud backwards. Short end threads are specified differently as interference fit and should go into the case. Long threads should be exposed.

[ROW911SC]

Thanks, Michael. That explains why I thought these looked too long...