cam nut torque

[sanders]

Advice from to old school former Brumos race engine builder, when torqueing cam nuts "put your shoulder in it". That should be wellll beyond spec. Anyone ever have a cam nut come off in a race or any motor?

[edmayo]

Very early spec called for 75 lbsft. I've seen at least one come loose, we go to 100 lbsft. and if I'm not mistaken Porsche may have upped it at some point.

[Jon B]

... and if I'm not mistaken Porsche may have upped it at some point.

The original 65 spec was 10 mkp (meter-kilopond), equal to 72.3 lbs-ft.
The final spec by the late 70s was 150 Nm, equal to 110.7 lbs-ft or "put your shoulder in it" ;-)

Jon B.
Vista, CA

[66S]

Ive seen one come loose ( not my build), we theorized that the washer wasnt centered properly within the sprocket shoulder, do pay attention to that.

[sanders]

Thanks all. Interesting tools used by the old schooler, two foot extensions on the cam holder and the breaker bar. Think 356 flywheel gland nut kind of torque. Seriously, I'm thinking he probably achieved 200 ft lbs or so. My questions are about nuts coming loose and is that much torque on a race motor a good idea?

[edmayo]

Sounds like a moot question, since we really don't know what the nut was torqued to. Why do you think too much torque would hurt a race motor?

[Jon B]

Interesting tools used by the old schooler, two foot extensions on the cam holder and the breaker bar.

An engine builder should own & use appropriate tools, especially the basic ones.
Here's an appropriate old skool breaker bar.





Jon B.
Vista, CA

[sanders]

I'm not concerned about too much torque, I'm concerned about my ability to apply that kind of torque at my age (strength). If there is a report of nuts coming loose on race motors with lesser torque I'll go get the kid next door to help.

Let me share the backstory as to why I'm asking. I've been racing the 911 for 31 years and I have always used factory torque specs on the cam nut. I have never had one come loose. In a bull session with the old schooler we discussed cam nut torque. Have I just been lucky or is factory spec all that is needed? I thought the racers in this community could weigh in. Thanks again.

[sithot]

Calling Archimedes!

[Frank Beck]

This thread reminds me of the '69S camshaft I have with the threaded portion broken clean off. I'll attach a pic to this thread after I dig it out. (No; we did not do it.)

110 lbs is PLENTY.


BTW: Last year had the large bolt come loose on a late cam on track. 8500 RPM 2.5. Didn't hurt one titanium valve.

Absolutely AMAZING.


After that we started using Lock-Tite and torqueing to 110 as well.