Use of Bearing Retainer

Yes Andrew I have used locktite 680 on the layshaft bearing. The case was so worn that the bearing would just fall out cold. It was so loose that I could move it sideways with my finger inserted in the inner race. This was the condition I inherited! As I didn't intend doing big mileage on the Atlas,I went down the locktite pathway. Because of concerns over alignment I elected to fit a quality ( Japanese I think ) ball race. I put plenty of locktite on the outer race, fitted the bearing and then stood the case vertical so that it would hopefully set centrally. Yes I know if the bearing fails I will have a job removing it but that's a risk I have taken. This was in 2008 and 10,000 miles ago!

Just wondering if there is a way of knurling the bearing housings to give a better interference fit. Maybe just a small amount of locktite in say three places in the housing would stop the creeping and facilitate removal at a later date.

On a new gearbox shell with the correct interference fit baked in I would not use Loctite as insurance, it will increase the interference fit and reduce the running internal clearance in the bearing causing premature failure. Use it for what it is intended, to restore interference fits in worn housings. Even then do not use it in alloy engine casings that get heated up as the heat cycles break the bond as the steel bearing expansion rate is less than alloy. So for a main bearing either get the steel outer ring copper plated or a new housing insert in the case.

Been there and got the T shirt in the 80's.

... of knurling. It seems to give an immediate improvement but as the contact is only on the peaks these are quickly flattened out and as the process is likely to remove metal (or at least displace it) you end up with a worse fit than ever.

I agree that if the interference fit is good then I wouldn't use loctite.

If the housing is new, needs to be heated to get the bearing in and the bearing stays put when at operating temperature I'd leave well alone. But for old housings, particularly if there any sign of the bearing slipping, I'll fit the bearing then run a little Loctite bearing retainer around the outside of the bearing race (with the bearing facing up) - it will insinuate itself into any slight gap that might be present. Wipe the excess away. If the housing is so loose that the bearing drops out unaided then bearing retainer on the outer race before fitting is the only answer short of sleeving the housing.

I would not be using a retainer on a new shell or where shows no sign of the bearing spinning. Most gearbox shells were cracked from manufacture. The trick is plenty of heat. 

… is the work of the devil. This is what some p/o did with the valve guides in my '72:

The left-hand cylinder head looked like someone had detonated a small hand grenade inside it.

At least it impelled me to get a very nice set of Colsibro guides and matching valves from JD Autoworx in Wallington

Andrew, if you're that worried about the possiblity of the outer bearing races spinning, have you considered a retaining screw? I'm sure I read of proddy racers drilling and tapping the case immediately adjacent to the bearing, drilling and tapping, and fitting a countersunk screw. As it also requires grinding out a small crescent-shape in the race itself, this is probably a machine shop job.

Michael's solution is described in detail for engine cases in Dunstall's 'Norton Tuning' - where he describes pegging the main bearings by milling a circular indent in the case and overlapping onto the edge of the bearing, and fitting a circular steel plug held in place with a screw tapped into the case.  The Manx 'M' Norton main bearings are supposed to have retaining plates with soldered screws.  I've not seen a picture.

Colsibro, very good, but best look up why it is used for valve guides. It is used for valve guides and has a big advantage but also a big compromise, that is why it is not used readily in the routine automotive world, if it was ideal every one from Ford to Dacia would be using it.

If you use colsibro, ensure the guide is under size so you can ream it to suit the stem, if it is standard bore when fitted then you have an expensive valve guide worse than any other guide you could have fitted.

… I see here: http://www.netbug.net/blogmichael/2007/05/15/bronze-giudes-in-cast-iron-cylinder-heads/

But the same source appears to suggest aluminium heads are safe, subject to Ashleys' points about suiting the bore to the valve stem.

Have I got this right?