Broken Cam Bearing Caps

redrover

Active Member
#1
A message of advice to all 2000/2200 owners. Don't over tighten the studs on your cam ('rocker') cover!
By the looks of it, the seal is made by gently compressing the cork gasket. However, the 'seal pressure' should be generated ONLY by the three rubber 'doughnuts' under the 'cups' beneath the dome nuts. Simply tighten the dome nuts until the rubber doughnuts begin to bulge, but no further. If you tighten them down until it 'feels arm tight', you will not only crush the cork gasket, but also introduce a damaging shear force across the bearing caps.

As I discovered today, the bearing caps can crack or break completely, causing a terrible rattling noise that makes your engine sound like a diesel! Thankfully no damage to the cam or bearing appears to have been caused on this occasion.

In all instances, I would wholeheartedly recommend one of the new neoprene rubber gaskets sold by Wins & MGBD, as this compresses much more consistently than cork and can also be reused almost infinitely. You should also renew the three rubber doughnuts while you're there.

Saw a hairline crack around the threaded holes from the retaining studs. When I screwed the stud back in by hand, the crack grew!


It really didn't take much effort to part the bearing cap in two completely. Note I had already removed the head studs by this point.


The bearing cap completely in two.


Lifting one side of the broken bearing cap away after unbolting it from the gallery plate on the rear.


The broken cam bearing cap. As can be seen, the threaded hole for the cover retaining stud is drilled right through the casting causing these three particular caps to be much weaker than the other two solid types.


The rearmost bearing cap removed. The second and fourth caps are solid types and much stronger. The front cap is the only one to still have the stud correctly in place. The nuts on the other two must have seized on making it much easier to remove the whole stud. The studs are open to the pressure lubricated cam bearings so the threads are permanently lubricated at that end.


No visible damage appears to have been done the bearing shell - the rattle only developed on the way home from the NEC last week - but it has been replaced anyway in case of ovality.


Cheers
Michael
 
#2
Do not try to torque the cam cover nuts to 10 ft lbs like is printed in the book. In my experience you crack the cam bearing caps before your torque wrench will click. Just snug them up so every things looks tight with a quarter inch drive wrench.

James.
 

redrover

Active Member
#3
j_radcliffe said:
Do not try to torque the cam cover nuts to 10 ft lbs like is printed in the book. In my experience you crack the cam bearing caps before your torque wrench will click. Just snug them up so every things looks tight with a quarter inch drive wrench. James.
10lbft! That's absurd. Does it really say that in the manual? Is that the Haynes guide or Autopress book? Don't think I've ever seen that in the factory work shop manual. If you looked at the gasket and rubber doughnuts it should be obvious that they don't require a torque setting, but I suppose having good condition doughnuts is key...
 
#4
redrover said:
j_radcliffe said:
Do not try to torque the cam cover nuts to 10 ft lbs like is printed in the book. In my experience you crack the cam bearing caps before your torque wrench will click. Just snug them up so every things looks tight with a quarter inch drive wrench. James.
10lbft! That's absurd. Does it really say that in the manual? Is that the Haynes guide or Autopress book? Don't think I've ever seen that in the factory work shop manual. If you looked at the gasket and rubber doughnuts it should be obvious that they don't require a torque setting, but I suppose having good condition doughnuts is key...
I think the 10 ft/lb is the value for the 5/16 bolts at the front of the cylinder head. I don't recall ever seeing a torque value for the cam cover, and I just looked in an early and late edition workshop manual and they are mute.

As an aside, the original rubber blocks were a softer durometer than the stuff you get now. NOS stuff has hardened from age, and the new manufacture stuff, like most repo rubber, is too hard. I always locktite the studs into the bearing caps with stud grade (red) so I know that it will take a serious ob=ver tightening to break the stud free and crack the cap.

Yours
Vern
 
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