Hey Folks,
A quick question;
Cam Cap bolts - are they reusable..??
I've set my Torque Wrench to 25Nm (18 ft/lbs) and one bolt has sheared and needed drilling out and two others have 'necked' badly.

Cheers, Dave.

 

Hi Dave,

I have always reused the cam cap bolts, and since the torque spec is 23 - 27 Nm / 16 - 20 ft. lb. you should be good at 25 Nm / 18 ft. lb.

My first thought is that if you have any oil in the cam cap bolt threaded holes, then one or both of the following may be happening:

1. Oil in the holes may be preventing the bolts from seating properly by "hydrolocking" them, since oil is nearly incompressible;

2. Oil in the holes may be leading to a false torque reading, allowing you to overtighten the bolts before your torque wrench measures 18 ft. lb. Torque readings are typically specified for dry bolts and threaded holes unless thread locker, thread sealant or anti-seize compound is specified.

Before you try torquing them again, clean all the holes thoroughly with brake cleaner, Q-tip swabs/cotton buds, and compressed air, and if you're still concerned, run a tap down every hole by hand until it bottoms out and then flush the holes again.

Cheers,

Don

 

Thanks Don - I've done as you suggested but found the issue somewhere else......
Although your suggestions would have caused my symptoms it turned out to be the Torque Wrench.
I've had a battered, old 1/2" drive Torque wrench for years but the lowest setting was 28Nm.
So, I bought a shiny, new 3/8" drive (12 - 88Nm) and set it to 25Nm. I've just brought it into work and checked it on our calibrated tester and the swine was 'breaking' at 40Nm despite being set at 25....!!!!
It is a 'known' brand - not some far East junk (it probably was made there....).
It will be getting sent back.

Cheers, Dave

 

Hi Dave,

I actually meant to ask about your torque wrench but forgot. One thing to be aware of is that most torque wrenches are certified for accuracy only between 20% and 100% of their range, so a typical 3/8 inch drive torque wrench that measures up to 75 ft. lbs. is not considered reliable at or below 15 ft. lbs., and 18 ft. lbs. is close to that suspect range. If your wrench is calibrated to 100 ft. lbs. then you were definitely in the untrustworthy range. Please keep us informed.

Cheers,

Don

 

Uh-Oh! I hope my harmonic balancer doesn't fall off - my torque wrench was maxxed out when I tightened it back up ...

Larry

 

If by "maxed out" you mean it was at its maximum torque measurement, you should be good. Torque wrenches are considered generally accurate between 20% and 100% of their maximum range, so a wrench calibrated to 100 ft. lbs. is accurate between 20 and 100 ft. lbs. It's the range between 0 and 20 ft. lbs. where the wrench would not be considered accurate and should not be trusted.

If I recall correctly, the SAE considers a torque wrench accurate if its measurements between 20% and 100% of its range fall within 4% of the graduated torque value, so roughly 96-104 ft. lbs. at a graduated 100 ft. lb. value. I think my Precision Instruments beam-type wrench is rated at 4%, my CDI and Snap On click-type wrenches are rated for 3% accuracy, and my Snap On digital torque wrenches are rated for 2% accuracy. The most accurate torque wrench I own is a Snap On (made by Precision Instruments) dial-type inch-pound wrench rated for 1% accuracy.

 

Don, Think it was set at 150? Anyway it was dialed in at whatever the maximum setting was.

cheers

Larry