Camshaft bearings.

[dougal9887]

Just fitted the new bearings. Inlet side is fine but on the exhaust side the oil drilling doesn't line up fully with the hole in the shell. All shells are the same. Should I worry? Pic attached. (Shells supplied by QED)

Exhaust cam oil drilling and shell mis-alignment.

Dougal.

[AHM]

What were the old bearings like?

In the head I have here the drillings are on the same centreline as the studs - So it looks like the drilling in the head is off.

It hasn't destroyed the head or cam so far so is probably ok as is... Its lasted 40 years!

[john.p.clegg]

Dougal
Don't worry,.......but if you're stuck for something to do,there's nothing wrong with a small round file and aligning the holes better....

John

[dougal9887]

Ok thanks.
I'll adjust with a small file. That shouldn't reduce the bearing area too much.
No idea how the old bearing lined up as I chucked them when stripping the head. No real sign of wear but, as originals, time for a change.
Dougal.

[AHM]

The hole also alignes with the groove in the camshaft, so you may be better filing the hole in the head

[oldchieft]

The down side of dealing with filings in the oil way would give me pause.

Jon the Chief

[john.p.clegg]

AHM
If you were buying a head would you prefer a filed camshaft bearing or a filed head? The end result being the same?

and as John says you have less chance of swarf in the oilways if you do the bearing on the bench away from the head..

John

[Mick6186]

My big valve head is exactly the same with the holes apparently out of line. The cam bearings look fine with no excessive wear. If the holes are enlarged won't this increase the oil flow so lowering the already lowish pressure in the system. Also is it wise to increase the oil flow to an area that is know to have the potential to leak like a sieve!!
I'm leaving mine alone. ' If it ain't broke don't fix it'.

[elangtv2000]

If you are concerned about slightly enlarging the oil hole in the bearing, note that most wear on cam bearings occurs with the top shell.

[john.p.clegg]

I'm sure it was Colin who extolled.... "oil flow is good for lubrication,oil pressure is good for finding leaks"....

John

[AHM]

John,
The end result isn't the same.

If I was going to correct the problem. I would strip it and clean, so there would be no swarf.

[rgh0]

There is probably no problem with the way it is as there appears plenty of area for sufficient oil flow and if there historically has not been any issue then it could stay the way it is. When you do the long bolt conversion on competition camshafts you restrict the oil passage into the cam substantially more than the bearing hole misalignment you have without problems.

If you really wanted to correct the alignment then I would not play with the bearing shells. i would adjust the oil hole in the head. while it is possible to plug the oil passage to catch the swarf and then pull all the swarf out with the plug I would preferably only do this with the head removed so I could 100% verify any swarf had been cleaned out properly.

cheers
Rohan

[oldchieft]

The down side of dealing with filings in the oil way would give me pause.

Jon the Chief

I would preferably only do this with the head removed so I could 100% verify any swarf had been cleaned out properly.

cheers
Rohan

Those are the thoughts I would pause to have.

Jon the Chief

[dougal9887]

Thanks for all the replies.
The head is off and about to be built up.
It would seem strange if my 1972 head was peculiar in this respect since I would presume all drilling in production would have used a jig and indeed Mick has posted a similar finding.
Since no particular problem was noted on the previous bearings, I'll probably leave it as is.
Dougal.

[rgh0]

The dimensional tolerances on the head machining was not great. There is significant variation in key items such as valve spring pocket depth, so some variation in oil passage drilling does not surprise me. I must go through my spare heads and see how much variation there is.

cheers
Rohan