The last couple of TY 4s I.ve built all have had a problem with the thrust cam Bearing. The side with the shoulders is always too tight. The cam will not spin freely . The other side , without the shoulders spins free. I 've tried three different brands and they have the same problem . The used ones have the gray finish warn but they spin fine. AL

Never toss out T4 stuff. Never know when the used parts are better than the new ones.

Single thrust or double thrust? Lay a sheet of 220 wet/dry sand paper on a sheet of glass. Put a few drops of oil on it and sand off a few thousands from the shoulder until you get close to the clearance you need. Polish the end with 400-600 grit.

+1 Yep, just sand it, clean it, then install it.

What cam are you running? As you know anything NOT spinning freely is never a good thing. I would be somewhat hesitant sanding the shoulders of the new cam bearings, but also not sure where else to go. Let us know of your results

....don't forget the "tap a tap a" to seat the bearings after they get a light sanding
no video
1) lightly side one side of the cam thrust and try to fit in case half
2) rotate cam for bind or cam/ bearing lifting out of case
3) little sand opposite side and check fit
4) rotate come and check for bind in case 1/2 or cam /bearing lift out of case
5) once the cam is spinning and no longer lifting, use a brass or aluminum punch or wooden block and give the front of the cam 2-3 light taps to to seat the bearing.
6) repeat the 2-3 taps at the base end of the cam
7) measurements or about 0.002 is the goals for endshake of the camshaft
8) repeat above till the desired endplay in this 1/2 is achieve
9) repeat above on the other case 1/2 if using a double thrust ( a quick measure meant of the "good" thrust bearing will speed things up)
10) when assembling the case 1/2s together a final check of the end pay can be performed


If I fit another set, i would fit the back side of the thrust bearing furthest from the gear, as the face closest to the gear will get the force from the angle cut gear
I hope this helps

not mine, but worth a look
https://www.youtube.com/watch?v=t0d87g-iCrc&t=274s