View Full Version : TR4/4A I Replaced the Cam Bearings

05-09-2019, 12:45 PM
I had this done at a great shop but they look strange. I see three bearing holes in at least two of the bearings--the one for the locating bolt, one dry one I can't explain, and a smaller one to the oil galley. It looks like the shop may have needed to drill the one to the galley, but I can't tell. I'll call and ask them. It's a bit smaller than the other two.

Should they all line up, or is some machining typically needed? It's too awkward for pictures since a couple of the holes (maybe all) are on the upper part of the bearing.


05-09-2019, 01:20 PM
Well, I took another look. They definitely got the bearings off somehow and then drilled one hole bigger and another relocated for the galley. They may tell me they had no choice. It appears close, but one of the locating bolts appears to have given them a problem, so they made that hole a bit larger, then relocated the oil galley hole. I'm guessing, since they do know their work, that they'll tell me the extra hole and widened hole will not impact life or performance and that if the cam can ride on two holes in any given bearing, it can ride just as well on three. Any thoughts there? Will I be 110 years old before this is an issue?

05-09-2019, 01:51 PM
There should be NO machining required. If the inserts are properly installed, all the holes will line up (except the one blind hole, of course).

But it isn't obvious that the rear bearing has a front and back. The ones I've gotten are not marked, but if you install them backwards, one of the holes won't line up. Took me 3 or 4 tries the first time to get it right. IIRC the center bearing (which does have an unused hole, the insert is the same as the rear bearing) can go either way.

Stuffing in apparently wrong bearings and then poking holes in them strikes me as sloppy work. Might be OK tho, if the cam spins absolutely free (without lifters of course) and all the swarf got cleaned out. The clearance to the cam journals is pretty tight, though, and it's easy to distort the inserts, especially if you install the locating pegs with the insert not lined up "just so".

05-09-2019, 01:55 PM
OK, thanks. I'll see what the shop says.

05-09-2019, 04:48 PM
OK, here is the answer. Cam bearing was off a bit and was too difficult to adjust and they felt it would be unnecessary to press it out and reset it because they were able to remove the oil galley plug and carefully drill into the underside of the bearing for access to the oil galley. Everything was done properly Iím told, with machining and chamfers, All shavings were cleaned and removed entirely from the block. The machinist says heís positive everything will be fine.

Iím trying to imagine how you can access the oil galley by using a drill in the oil plug hole, but they say there were no new holes put in the galley or block, and that the only access was through the plug hole.

Does this make you nervous?

05-09-2019, 06:08 PM
May I ask the reason for replacing the cam bearings, as that has ramifications on correct camshaft installation.

05-09-2019, 06:37 PM
It's been awhile since I looked, but I think that is right. The plug in the side of the block is where the factory drilled a hole from the oil gallery through to the rear cam bearing, as well as another hole down to feed the rear main bearing.
The other important hole in the rear cam bearing could be accessed with the head removed, by drilling down through the oil hole in the back of the block.

That's the one that's hard to see; and it seems they didn't mention it ...

05-09-2019, 07:26 PM
That last hole Randall is referring to is extremely important as it provides oil up from the rear cam bearing through the block then into the head and oils the rocker shaft. If that hole is not properly aligned , you get no oil to the rocker shaft.

05-09-2019, 09:49 PM
Yes that rear hole is open and fine, all the way to the rocker. I think I can keep trudging forward. Iíll spin the cam first per Randallís Suggestion.

05-10-2019, 09:07 AM
The story you get from the shop is not always completely accurate.

The shop that pickle my TR3A motor returned it with what looks like a plumbing plug in the water jacket opening in the head. There is normally an aluminum plug there.
When I asked the shop they denied all knowledge of the plug. In their defense I did not check it before I dropped it off so it could have been the PO.
I could not get it to move so as it is not leaking and the valve cover fits I have left it.


05-10-2019, 05:00 PM
Those bearings can be installed at least 12,389.7 different ways, maybe more, and only one is right. Then, it's a real pain to get them aligned so that all the oil passageways are clear. Like (probably) everyone else, I had to install some of the bearings a couple times before they were right.

Anyway, here's my story, with possibly some useful info:


Scroll down a bit to the camshaft section. I hope it's all correct; it's so confusing that even now, after doing it a couple times, I wonder.

05-10-2019, 07:36 PM
A "great shop" should not resort to drilling a bearing....maybe not so great.
I was fortunate that a specialist machine shop was not far away from where I live.
They do work on exotic engines, including manufacturing bearings etc.
They remetalled my old bearings, inserted them into the bare block as per original fitment, then line bored the cam bearings in situ to exactly fit my camshaft. It's a similar way as you would have your engine block tunnel line bored [if necessay] for perfect crankshaft/bearing fit.