For an A15. I have a new set of aftermarket cam bearings. Factory service manual sez to hone cam bearings after replacement but maybe that is assuming factory cam bearings? Anyways, is this always required?

Fsm says to line-hone them. Otherwise the can will bind. It also recommends not replacing them as it is not part of an engine rebuild - they almost never go bad.

Thanks. This goes to how I clean the block, which means I just have to clean it manually instead of having it hot tanked.

The 'deal' is sort of along the lines of making sure the cam can spin freely. The bearings 'should' be fine, but the actual process of installing them can slightly 'warp' the bearing at the edge that was 'pushed on' to force (probably a better word than that is appropriate) it into place. So it's more a case of running a reamer through it to clean up any of this. As a general way to sort this, have a used cam around and after teh bearings are installed, apply a light film of oil, and see if you can fit the cam into the block, and that it rotates freely, if you can't insert it into the bearings, it (obviously) needs to be reamed (or whatever the word is) and if it doesn't spin freely it's also the case (but to a slightly lesser extent).

Any engine reconditioner/machinist shop would be able to do that and it wouldn't cost the earth. Years ago, the first time I ever rebuilt an engine, which was acid dipped, so it needed new cam bearings fitted, the shop that fitted them specifically asked for a cam for it, so they could check the clearance afterward and hone as necessary. It wasn't a particularly common engine, and for many of them they already had a factory cam to suit it for this very purpose. You should still test fit the 'real' cam afterward, and check it spins freely, but generally if the original/stock/used cam fits you are in teh clear.

It's true they don't tend to wear much, but if you are going to run a more agressive cam with faster lift rates and higher valve spring seat and nose pressures then obviously they'll be under more stress, and relatively speaking, cam bearings aren't much of a cost difference.

After they are all installed, esp if the bores have been honed (presumably this would be the case) make sure to clean the bores etc. Not just with a solvent. This won't get some of the machining debris. The only way is hot soapy water and a stiff nylon brush. If people aren't sold on that idea, an alternative could be to alternate a couple of hard scrubbing sessions each, with hot soapy water and then solvent and finishing eventually with the last round of hot soapy water. Clean out the bores at the end with clean white cloth, and if that cloth comes out with any debris or staining, it means that the job isn't complete, and it needs another go around. Once you finally get the rags coming out spotless it is 'ready'. At that point blow it out with compressed air, and it wouldn't hurt to hit it with a light coat of wd40 to stop any trace amounts of surface rust before the rebuild/reassembly takes place.

I know it sounds like a pain, and granted, it will 'work' if you don't go to that extreme, but I kid you not, the amount of debris left in teh fine cross hatching of a freshly honed bore, if not cleaned out thoroughly will probably cut ring life in half. That's still a long time mind you, and most people would be happy with that, but my take is that for the extra few hours spent doing it that way, it's gotta be worth the literally tens of thousands of miles extra engine life. I realise this is off on a tangent from the original question, I hope the info is of use to someone. It sorta came to mind when thinking about block prep in general and I thought I'd throw it in.

Nicely written John, motor oil seem to floats away the abrasive debris very well so I also wipe with it.

In general, I try not to change cam bearings unless really needed.

Good stuff and just to add for the block cleaning, Ive used a high pressure gerni throughout the block, then high pressured air and finally put it in an electric oven on very low heat (I often use my tennis club oven on weekends as the old chooks arent around) for about 10 minutes then let it cool down by itself. A water repellent I found is way cheaper from 2 dollar shops and leaves a nice film that prevents rust. On stock factory everyday engines, cam bearing suffer very little wear if any compared to crank bearings.

Thanks all for the info!