Fitting Main Bearings

I would like to know how you Guys feel about fitting main bearings in to new and used crank cases using Loctite.

Cash

I've never had the luxury of assembling new cases and secondhand sets have always seemed to show the dull grey surface that suggests some sort of movement between bearing outer and case but I've never had actual spinning.

With this in mind I always use Loctite when assembling. It does make dropping the bearing in a bit of an 'all or nothing' affair. It's not possible to put Loctite on warmed cases as it rolls off so I put it on the bearing but if it doesn't drop in cleanly first go then it has to be removed, cleaned and tried again.

I have noted the symptom of newly assembled engines appearing to lose their end float as the case cools down. I don't know if this is down to simply the ground and as yet unpolished bearing surfaces or if the extra interference caused by the Loctite has an effect. End-float is restored when warm and after a few hundered miles when cold and I've never found ill-effects.

Not totaly sure about your question but I love loctite but I don't really like useing it on heated to fit cases as I find it dries quickly and forms a thicker than required layer taking up bearing clearance, if the bearing slips in cold or nearly I prefer to freeze bearing and locktite,you would hope that new cases were machined correctly and loctite was not required. Thats my 2 cents worth

Thanks for the replies.

I once used Loctite 648 ( high temp ) to install FAG bearings in heated cases .
After cooling the bearings where way too tight .

Click to expand...

I've had that experience too, and it was my worry, the NOC Commando Service Notes say the factory would loctite the outer ring in. That statement could come from pre-superblend days, who knows?

I popped the new bearings into hot cases dry in the usual way, a day later had both tightened up just enough to have made end-float checking a little difficult. After fitting the barrels I found the drive side rod was just catching the case. Grief, one step forward two back. I'll ring Andover Monday morning to ask if I can dress the high spot without effecting the warranty.

What can happen if you don't Loctite is the bearing moves a little bit. I don't think it actually hurts much. The amount an alloy case expands, flexes and stretches is amazing. I've only seen this in industrial equipment training videos, but there is a reason for the Locktite. In a situation like this all it does is give the outer bearing some traction if the clearances are correct. If the Loctite is used to make up for missing metal it's a bit different. All you would need is one drop to help prevent spinning, and one drop spread over the surface of the bearing should not effect clearance much. Some folks have been known to do a thick bead of Loctite and this will noticeably affect clearance.