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TR2/3/3A Cam follower rotation

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LionelJrudd

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Are the cam followers supposed to rotate in operation?
The ones I removed from my old block are generally grooved slightly as if the have been sitting in the same location on the cam.
I have spare followers which I have polished and will use but would like to know about their correct operation. I know some later cam followers in other vehicles had a rotator in them to facilitate this.
 
Yes, they should. The lobes are ground with a very slight taper, and the lifters with a very slight dome. This keeps the camshaft pushed rearward and causes the lifters to rotate. If they don’t rotate, it won’t hurt the engine, but they will wear faster.
 
Thanks John. I thought it was something like that but could not remember the detail of how it worked. Makes you wonder why they wear like that. Perhaps the cam has been ground flat. When miked, it is still standard dimensions on the bearing journals and in very good condition but the followers are worn.
 
Yes liters should rotate. But taper and radius comments is not true if discussing OE parts, both cam and lifters are ground flat if original equipment parts are being used however many aftermarket cams are ground with a taper and lifters are ground with a radius on the mating surface. Wet liner 2 thru 4A blocks lifter bores are offset to the centerline of the cam lobe which causes the lifter to rotate as it contacts the cam lobe. I've read that European engine builders used flat cams and lifters with offset lifter bores while Amearican builders used the taper and radius approach to create lifter rotation. The last rebuild I did I was careful to copy the Triumph approach using a reground original cam (flat) and reground lifters (again flat). Due to a head gasket failure I had to pull the head after about 4000 miles and found that the lifters had a nice pattern of rotation showing. I'd suggest only using flat ground parts but if using aftermarket cams and lifters at least match them with lifters from the cam manufacturer for that cam.

I have no opinion on what effect the offset lifter bores have with the aftermarket parts. I do suspect the contact points between cam and lifter will be different than what the cam manufacturer designed and that might have an affect on lifter rotation. And what is most important is to follow the procedure for cam and lifter break-in upon initial engine start up as well as using the correct oil with the required additives designed for flat tappet lifters. Most folks use Brad Penn 20W-50 with ZDDP.
 
Thanks for the feedback Jerry. I had vague recollections about the offset aspect you describe. Interesting to hear of the two different approaches to effect the same outcome.
The lifters I am using are originals as is the cam so I should be OK. Will head your advice regards correct break-in procedures and oil. Regards, Lionel
 
Lionel, You stated the cam and lifters are original, are they new or used and if used are the lifters the same as was originally installed with your cam and are they numbered to go back in the original lifter bore location? If you've mixed them I'd suggest buying new stock from TRF or get your original ones re-ground flat by an engine shop. I've seen the TRF original lifters and believe them to be ground flat. The upgraded lifters that have a small hole in the side that others sell are radiused ground.
 
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