Camshaft bush line ream services

Thanks for that Ian, I did actually speak to Norman about something else recently but he is snowed under with work.

I looked at buying a 7/8 (22.225mm) reamer and rigging up a guide to line ream, still not as good as a bespoke line reamer, but also a H7 tolerance 7/8 reamer would very likely give an oversized bore.

I  decided to line bore the bushes in my mill, I see from the info here that the clearance between cam journal and bush should be 1.5 thou. The case mis alignment with my cases is around 1.5 thou with the cases clamped together, the supplied bushes dont have enough material on them to take this out, if the bushes were a bit more undersized this wouldnt be a problem. This would still be a problem with line reaming.

I can only see that making your own bushes with enough meat to take out the misalginment is the solution or maybe the original Norton bushes have more meat on them.

Does anyone know what material the bushes are made from, I was guessing phosphor bronze?

I see someone else had this problem on a post last year , I dont seem to be able to cut and paste it,( under Dominator 99 camshaft bushes)

As I didnt have a bespoke Norton line reamer and there wasnt enough material on the aftermarket bushes to line bore effectivtely I decided to make my own bushes and line bore them so the correct (1.5thou) clearance.

I made them from sae660 bearing bronze in the lathe and line bored them in the mill, not a quick job but Im very satisfied with the result and was able to do it all in my own workshop.

I still dont know why the cam started to flake the lobes and also had badly worn journals and knackered the bushes but I very much suspect it was incorrect heat treatment and very thin case hardening as I was able to easily file a small flat on the journal.

I have now fitted a newman chilled iron cam.

Heres a couple pics of the offending cam and damaged bushes, it was assembled with assembley lube, run in correctly and had only done around 2500 miles. I inspected all the other bearings including the big end shells in case contamination had caused the damage but all good so can only suspect the cam, tge case hardening seems wafer thin as I was able to file a flat very easily on the journal. The other defect with this cam was the shoulder of the scroll was in the wrong position by .65mm causing the cam to lock up when torqued, I machined the thrust washer to give the correct end float. Probably should have sent it back in hindsight but no other cams were available at the time