TR4/4A Cam Bearings

[KVH]

I earlier said my block and bearings looked terrific when I disassembled everything. Well, looking closer now at the cam bearings, I'm seeing a little scuffing and I feel some abrasions, maybe like .001 or so. Not gouged by any means, but some abrasions.

I'd hate to mess up the cam freeze plug, damage the block or commit some other atrocity just because I want to be neurotic and address everything, but since I'm this far must I replace those cam bearings?

If so, how to I do it myself so I learn something? What tools do I need--or should I just break down and take it to the shop?

 

[Jerry]

On most of my British Engines, I have the bearings replaced. IE: it requires a long driver to get the old ones out and a VERY long reamer to fit the new ones. Probably not tools you would use for anything else. An exception to replacement is when I would know that the engine is low mileage. My attitude is that I am rebuilding it now and I would rather have it right than have to go back. Poor bearing clearances can result in lower oil pressure .
But, I am not an expert. Rebuilding these engines usually cost me about $2500 in parts and machine work.

Jerry

 

[charleyf]

One more complication on the cam bearings is that they MUST be properly oriented when in place for the oil to maintain flow in the engine. So just taking it to any machine shop requires diligence on your part to make sure they understand the job at hand.
For myself a few more dollars in a total rebuild is worth the knowledge of the newer parts now running in the engine.
Charley

 

[TR3driver]

I made up a pair of mandrels and used a length of 3/4" threaded rod to pull the old inserts out, then pull the new ones in. No reaming required. As Charley notes, it is important to get the inserts correctly oriented, particularly the rear one as it also passes oil to the rocker shaft. The slots for the retaining pins must line up close enough that the pins don't foul on the side and crush the insert. Took me a couple of tries to get them just right; fortunately the puller doesn't damage the inserts.

Unfortunately, I left the puller at Dad's house and can't find it now. Possibly it was in the tool box that got stolen. I'll have to make a new one when the time comes again.

 

[malbaby]

IMHO...the only way to replace the cam bearings properly is to take the block to an appropriate engineering shop... have the old bearings removed and remetalled, then installed in the correct orientation, then LINE BORED to suit your camshaft.
It is not possible to achieve the correct tolerances on the camshaft any other way.

 

[TR3driver]

Whole point of the replaceable inserts is to avoid having to line bore ...

 

[JerryVV]

My experience mirrors Randall's having to make a few try's at getting it right. In my case the bearings would rotate as they
were installed so I needed to gage the rotation such that when installed the locating holes and the oil holes lined up with the correct spots in the block. It's been more than 20 years so far and all's well.