Advice

[les]

Installing cam bearings, front and rear done, it appears that these bearings are designed to close to the correct clearance, and I think they do. However, when threading the cam through, ( the centre bearing is not in yet) the bearing by the oil pump feels just that bit tighter than I’d like. I’ve found the high spots with engineers blue. My question: in the final stage, what would be acceptable to lap in the bearing, obviously I don’t want anything that would leave residue in the bearing surface.

[philthehill]

Les
A suggestion
If you have an old camshaft - grind a reasonable width fore and aft angled (towards the direction of rotation) slot in the camshaft bearing surfaces, fit the camshaft and turn - any high-spots of the white metal bearing will be removed by the sharp leading edge of the slot. The I.D size of the camshaft block bearing diameter will not be compromised as the tip of the slot will not be larger than the camshaft.
Use a slip stone to sharpen the edge of the slot if required.
Use of the slip stone ensures that the possibility of radial marks created by the camshaft slot is reduced or eliminated.
Modifying a camshaft as such results in a tool very similar to the BMC camshaft special line boring tool.

The other way of course is as you already have the engineers blue is to scrape the high spots away with a bearing scraper.

Phil

[les]

Thanks for the prompt suggestion Phil, that sounds like a neat idea. I’ll see if I can find an old camshaft.

[les]

As a follow up, for interested parties! Managed to buy a cheap camshaft and modified it as your brilliant idea Phil.
The grinding produced a slight burr on the journal but prior to stoning I thought I’d enter the cam an eighth of an inch or so to feel what was happening, it produced a few score marks, so I removed and stoned the journal smooth, tried again and all went well. Now the cam turns nicely. However now I’m not happy with the score marks from the first mistaken attempt, which are now annoying me, splitting hairs I know but I’m fitting another bearing!

[philthehill]

Les
You are too hard on yourself but I would do exactly the same.
Glad it all worked out well in the end.
Phil

[les]

These things play on my mind. I’m well pleased with the ‘tool’ though.