Cam Cover Plugs Crack with Torquing?

[OK-944]

Just got the cam cover back on my engine...got it nicely torqued down, after which I installed and hand-tightened the six threaded plugs which provide a seal over the six cam bolts which are located within the head. I then proceeded to torque down the plugs.

Three of these plugs torqued to the specified 29 lbs. with no issue...but the other three basically "collapsed." When I removed them, I noticed that the female threads on the cam tower are fine (whew!), as are the male threads on the suspect plugs...but the plugs themselves are basically cracking apart.

(I'd tested the torque wrench earlier with an electronic torque indicator...plus I basically know what 29lbs. feels like). I'd always suspected that these plugs might be a bit too soft to be torqued to 29lbs., but I also try to follow specs as closely as I can.

Anyone else have this issue?

[OK-944]

Hmmm...I did run the tops of these plugs over a succession of sandpaper grits (220/320/400) to smooth them off a bit. I wonder - did I remove some kind of strengthening treatment layer?

[wildcat077]

That seems like a lot of torque for the plugs ... they have no structural purpose , they only serve to cover the access holes , are you sure you didn't overtorque them ?

[9FF]

That’s too much torque. Are you sure you haven’t read Nm and applied it as ft-lbs?

[944 Ecology]

The published torque is 40 Nm or 29 lb-ft of torque.

While it seems kind of high, that's the number.

[9FF]

Originally Posted by 944 Ecology

The published torque is 40 Nm or 29 lb-ft of torque.

While it seems kind of high, that's the number.

I read a while back that the published number was wrong, I’ve been searching for the post but can’t find it now. I only know as I corrected the number in my manual after I saw the post. I’m pretty sure though it should read 29Nm.

[jjeffries]

Maybe I’ll eat these words after a future mechanical failure of my own making, but I’m leery of being too dependent on torque wrenches. Their use can cause the mechanic to miss feedback the threads are providing. When I assembled my 911 engine I used (very nice, borrowed) torque wrenches for all the important case, can and head fasteners and before that had made sure the threads were all in A-1 shape. And I’ve learned what 80 lb/ft feels like to tighten wheel lugs; muscle memory can be every bit as useful as that clicking or beeping wrench.

Best, John

[OK-944]

I agree that the published torque specs for these plugs are a bit too high...so I'll probably torque the new set I've ordered to about 20 lbs. Thing is, these plugs act in concert with aluminum crush washers and need to hold cam housing pressure - so they do need a bit of torque.

I'll likely also make sure that the crush washers are smooth on both sides, and that the mating contact surfaces on the cam housing are likewise smooth - to realize a good seal without going overboard with torque.

[wildcat077]

I've removed my cam towers over a dozen times on three different engines and i always tighten the plugs hand tight plus a quarter turn or so , just so they're snug and i've never had any leaks so far.