Reaming cam bearings

You could get the cam journals ground down. Or pollished with an emery tape.

As the case heats up i would expect the clearance to increase, in any case as cams seem to vary in quality and life i would anticpate the next cam may be smaller so i would leave the bearings as is.

A difference of 1 thou can make a no go into a go, but clearance is needed for the oil , what is the running clearance supposed to be??.

Previously wrote:

First time on here, though long term owner. I am scratching my head as I am fitting a new cam in my mercury and because the old cam was a few thou down on the journals (in places 22.11mm), even after wear the new one (22.20mm) is tight in the drive-side bearing (pretty tight in the timing side bearing too), I can barely turn it by hand even without worrying about fitting the other crankcase half. I reckon I could do with opening the bearing out by about a thou, and I would be in business. So how best to do this?

I have various ideas, from making my own in-line reamer using a home-made D-bit for the reaming, to marking the bearing with engineers blue and scraping (a little tricky to get at it). I wonder if there are any other cunning wheezes people have thought up (making a reamer out of the old cam is one cunning plan). Of course if there is anyone in Cheshire who has an in line-reaming tool, then there is a pint in it !

I should perhaps say that I don't like the idea of using abrasives or hones in case any particles get embedded in the bearing, but maybe I am being over-cautious.

Hello the easy way is to put your crankcases in the Oven of gas mark full or electric oven on full for about 40 to 45 mins then have a nice flat peace of wood like a off cut from a 8 inch plank about 8 inch squire in all and you need some engineers leather gloves so when you get the crankcase out of your oven all you need to do is just tap it on the wood and it should drop out . if not you can use a raw bolt that on a large side. the raw bolt screwed in the jaws open out and you can get a grip from the inside of the bush to pull it out by working it round do this when its hot . as it cools you may need to put the case back in the oven for some more heat treatment ,

Previously wrote:

How would taking the bush out help ? According to my manuals new bushes are supposed to be in-line reamed, so I don't see that helps me.

The problem is people dont always read the post properly before replying! and the bushes should be reamed in the cases

Previously wrote:

Previously wrote:

How would taking the bush out help ? According to my manuals new bushes are supposed to be in-line reamed, so I don't see that helps me.

The problem is people dont always read the post properly before replying! and the bushes should be reamed in the cases

The inline reaming is after fitting the new bushes .not the other way round . IE trying to take them out. yours anna j

see what i mean Steve !!

Steve,

I have just read your original post, you are changing the camshaft because of excessive wear in the journals, the cam has been in the engine since 1984 although you do not say how many miles you have covered, in all these years it would be fair to assume a few, from what you write in post number 5 you clearly know what you are doing.

The softer camshaft bushes will/should wear long before the harder camshaft, fitting a new camshaft in old bushes, assuming the new cam is made to the correct dimensions it would most likely be a rattling good fit, if anything after many miles you would find ovality in the old bushes.

Perhaps you should check the finshed size of your new cam against another new cam just in case.

I hope this has been of some help.

Tony