Re the outer crankshaft bearing, i wouldn't bother fitting a sealed bearing as not much oil seemes to blow past this anyway. M20 gearbox bearings in the past i have always removed the inner rubber seal, my thinking was that with the original oil baffle shim still fitted then this would keep most debris away from this bearing as originally intended. I may re think this now on my next build and leave both intact.
The cooling effect of the oil was one of the factors mentioned to me as well as the lubrication of the bearing....The intrusion of debris of any form into the bearings doesn't appear to be a practical issue when the engines can reach extended mileages without any attention....For example I didn't even remove the barrel and head from my B33 for some top end work until I had completed 78,000 miles on it after a rebuild...
It appears though, from the anecdotal evedence here, that either way serves OK...Ian
Was not me talking about breathing through the primary on an M20 .
I do it on all of the unit singles but they are different cases.
Seals in so far as a bearing goes is a misnomer
They are shields at best as none of them actually seal
I go through dozens of 6202, 6203 & 6204 bearings every year on ride on mower spindles where the idiot owners use those wash out ports on a hot deck so the bearings suck in the water as they cool down
If you want to stop debris entering then use a ZZ ( 2 metal shields ) as these do not pretend to be seals
The seals are designed to keep the grease in not contaminants out and ZZ's have lots of tiny holes .
I use them to replace 2rs on spindles where grease nipples are installed as the grease can flow through both the shields
If you use 2rs in the same situation the grease will cause the inner side to push in onto the race and breakup over time.
Similar story for the crankcase a zz will do a good job at slowing the sump draining into the primary but will not blow out when you try to start a wet sumped engine.
Now if Ian or others are worried about cooling use ZZ's but in reality the heat flow from the outer to the aluminium case will be orders of magnitude greater than between the balls & the oil
Next time you have the box out, remove the inspection cover , fill it to the corret height with oil and look at how much of the bearing would be in contact with the oil so you are really only talking about splash when going strait and very partial immersion when cornering depend how much of a cornering hero you are,,, on universal blocked tread tyres !!!!.
What is far mre important when selecting bearings is to get them from a trusted source , not evilpay or scamazon .
I can get 6000 series bearing from China for as little as $ 2 a piece , OK for shopping trollie but that is it.
And the most faked item on the planet is not Rolex watches it is brand name bearings so stick to the trusted names and make sure they come in a box .
['What is far mre important when selecting bearings is to get them from a trusted source , not evilpay or scamazon .
I can get 6000 series bearing from China for as little as $ 2 a piece , OK for shopping trollie but that is it.
And the most faked item on the planet is not Rolex watches it is brand name bearings so stick to the trusted names and make sure they come in a box'].
I agree totally with Trevors last paragraph...Branded bearings are the only way to go...
On the subject of the post generally, I took advice, decided to go with that and basically do what I have proven to work over time...I'll readily admit there may be other ways of getting to the same place though...Ian
