964 Head Stud Projection

[redjb944]

does someone know the correct projection for 964 head studs?? Wayne's book says 135mm for all head studs (but the book does not specifically cover the 964). I have a copy of a 993 manual and it calls for 130.2 - .05 projection...so I am confused at this point. and no, I failed to measure the projection before removing the studs...my bad!!

[winders]

The Porsche Tech Bulletin Part Identifier 1012 Number 9604 states that the correct height of the studs **above the cylinder spigot** is 135mm for 911's up to 1989 and 130.2mm -.5mm from 1989 on.

Scott

[Henry Schmidt]

For anyone thinking about doing this project with a better head stud, the Supertec stud has no prescribed install height, has never been reported as broken and has a lifetime warranty.

[Lapkritis]

You could also just measure the stack the fastener holds. It's not too bad.

[redjb944]

thanks for the quick response(s)...especially "Winders" ref to the Tech Bulletin. will go with the 130.2-.5mm, again, thanks.

[Green993]

FWIW, I did this a couple of weeks ago on my 993. I decided to aim for 130.35 (the midpoint of the range). All worked out, I torqued down the cam carrier first and then did the head bolts. I used red loctite to secure the bolt in the thread.

[cmonref]

How does this

130.35 (the midpoint of the range)

meet this standard?

130.2mm -.5mm from 1989 on

Looks like one or t'other is wrong.

[Green993]

Originally Posted by Brian K. Haggard

How does this

meet this standard?

Looks like one or t'other is wrong.

I took 130.2 - .5 to mean 132.2 TO 132.5. Am I reading this wrong?

Are you saying this means 132.2 MINUS .5?

[Henry Schmidt]

Originally Posted by winders

The Porsche Tech Bulletin Part Identifier 1012 Number 9604 states that the correct height of the studs **above the cylinder spigot** is 135mm for 911's up to 1989 and 130.2mm -.5mm from 1989 on.

Scott

The statement about <89 and 89> is somewhat inaccurate or at the least confusing.
There were two different 911 based engines built in 89. The last 3.2 Carrera and the first 3.6 Carrera 4. The 3.2 Carrera used the old style Allen nut and the 3.6 Carrera 4 used the new style and 12 point hex nut with integral washer.
Different engines with different requirements.
That said, shorter (within reason) is generally better than longer.
The proper length for your specific engine can be determined during the dimensioning stage of the engine build. It's easy to check while checking piston to head clearance because you are generally only working with one cylinder, one head and two studs.

[winders]

Wow, Henry. You always have to show how others are wrong. The text I used actually came from Randy Hubbard (Raceware).

I suspect most engine builders would understand that "up to 1989" would mean pre-964 and that "from 1989 on" would mean 964 and later. Also, in the context provided by the OP in the first post, it's pretty clear what is what.

Scott

[winders]

For clarity, if it was lacking, please look here:

http://cycle-planet.com/OT/cylinderheadbolts.pdf

Scott