TR4/4A Front cam bearing

[bammons]

Another dumb question from me. Why does the front cam bearing not come in the cam bearing sets? Does it not always need to be replaced even if the others are replaced? Is it a true "bearing" or more of a guide that is not as critical as the others? Would you always replace it if a new cam is used? Thanks Bruce

 

[TR3driver]

Definitely a bearing, takes more load than the others because of the chain drive. Often it's the only one that needs to be replaced, and in fact on some engines the others are not replaceable. I forget the change point offhand, but TR2 only had one replaceable bearing. So did TR5-250-6.

Check the fit of the new bearing carefully; it's what controls the end play of the camshaft.

 

[bobhustead]

The front cam bearing is, i think, pictured by Moss at part #827-000. It is different from the other inserts, being more beefy and mounted with two bolts thru a flange to the front of the block. We call them all bearings but they are bushes without any moving parts. I don't know the clearance specification, but it is listed for $99.00. Why scrimp with a new cam.
Bob

 

[CJD]

The specs are in the Service manual. I’d recommend taking measurements before replacing the front bearing. My TR2 was 60 years and 58k miles old, but showed no measurable cam bearing wear.

 

[TR3driver]

 

[bammons]

Bob - Yes it is $100 for a replacement. If I took the theory that I just replace everything that may or may not need it on a full engine rebuild/full car rebuild then that could cost me much more than $100. But I will of course replace what is needed that is why I am asking. I am just a parts changer not a mechanic and am attempting my first engine build. In light of Randall's answer and because I am replacing the cam I will order a new bearing. thanks for the answers

 

[TR3driver]

In light of Randall's answer and because I am replacing the cam I will order a new bearing. thanks for the answers

I didn't mean you should automatically replace it; just check it for wear. Don't think I've ever done an engine like John's, with only 58,000 miles.

 

[bammons]

Yes John's is very low miles for such a old car. Mine shows 85,000. Part of my concern is that this engine was rebuilt around 1980 and has very few miles on it since. It has been sitting. I do not know what was replaced or not. So if it was put in new then it would be virtually new now. But I am putting the BP270 cam from BPNW in it so unless it was like new them I should put a new front bearing in (cam bearing set from TRF is on the way). What is the tool called that measures the internal diameter so I could check it? Can I buy it cheap like at HF? Or should I just order a new one?

 

[TR3driver]

Kind of tricky, but this is what I use.
https://www.harborfreight.com/6-piece-telescoping-gauge-set-5649.html
Takes some "feel" to get it right; you have find the point where the gauge just catches in the bore as you move the handle through center. I always do it at least twice, and repeat if they don't agree.

But you can also get a pretty good idea by just slipping the bearing onto the cam and trying to wiggle it. If you can feel it move, it's probably worn enough to replace.