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+--- Thread: Rear main bearing - fitting (/showthread.php?tid=5103)
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Rear main bearing - fitting - Mick Hanna - 19-10-2020
I'm about to assemble the bottom half of my spare engine, a job I did on another engine about four years ago, but some kind of brain fade has crept in.
A) The Woodrow Manual describes fitting the inner roller race onto the crankshaft journal before fitting the bearing housing and outer race, whereas,
b) The Practical Classics article 'Engine Rebuild' (which records Ian Bancroft rebuilding the Austin Seven engine) shows the bearing housing with the outer race being fitted first and then the inner race is drifted on to the crankshaft journal.
I think I followed Ian's method before, but my question is: Does it make any difference or will either method work?
RE: Rear main bearing - fitting - Parazine - 19-10-2020
Can't see that it makes much difference. I usually fit the inner first, having previously fitted and removed the outer to check there won't be any problems.....
RE: Rear main bearing - fitting - Steve Jones - 19-10-2020
(19-10-2020, 01:44 PM)Parazine Wrote: Can't see that it makes much difference. I usually fit the inner first, having previously fitted and removed the outer to check there won't be any problems.....
And I normally do it the other way round but I agree, can't see it makes much difference either way.
Steve
RE: Rear main bearing - fitting - Chris KC - 19-10-2020
I'm tempted to say 'depends on your engine'... In my case the inner race goes on to the crank first then the crank is fed into the case and then the housing installed from the rear. Don't think it would be possible to do it any other way - but that's just my engine...
RE: Rear main bearing - fitting - Mick Hanna - 19-10-2020
Many thanks Parazine, Steve J. and Chris KC. I feel suitably reassured. It is a bog standard 3 bearing engine, by the way.
RE: Rear main bearing - fitting - Chris KC - 19-10-2020
On deeper reflection Mick I think the real question is 'how tight is your inner race on the shaft?' If it's nearly as tight as mine don't even attempt to install it 'in situ'. (And if it isn't....)
RE: Rear main bearing - fitting - David Witton - 19-10-2020
Mick my two pennoth. If the inner race needs some clouting when fitting on to the crank journal, then there is the risk of some collateral damage to the outer if you have already installed it. On the other hand, if it is fitted first, then when you come to fit the outer, complete with housing, and providing the c/case is properly warmed, it can almost be fitted with the minimum of persuasion. This allows you to take care when aligning the rollers in to the outer race. Hope that all makes sense!
RE: Rear main bearing - fitting - Bob Culver - 19-10-2020
Preservation of the front lip is paramount. Less potential brute force involved preinstalled. Provides a check of fit, opportunity to check clearance to flywheel etc.
(Outer housings are seldom truly circular. With a close tolerance bearing, tighter than Austin spec fit on shaft, may require some patience and lots of revolving of the crank to enter the outer.)
RE: Rear main bearing - fitting - Ian Williams - 19-10-2020
I never drift the inner race onto the crank, its a surefire way to eventually have a loose journal. I warm the race with a hot air gun until it is just too warn to touch, it will then simply drop onto the crank without any drifting and immediately cool securely in place. I then fit the outer by warming the case and it will also go in without force.
RE: Rear main bearing - fitting - Tony Press - 19-10-2020
(19-10-2020, 08:17 PM)Ian Williams Wrote: I never drift the inner race onto the crank, its a surefire way to eventually have a loose journal. I warm the race with a hot air gun until it is just too warn to touch, it will then simply drop onto the crank without any drifting and immediately cool securely in place. I then fit the outer by warming the case and it will also go in without force.
Excellent instruction.
As noted if the outer ring is put in place in the case first there is every chance of the hardened roller set sliding heavily across the hardened running track causing one or more scores and leading rapidly to early onset of the well known 'rumble'