E: Engine Main bearings

SteveO

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Having finally got the oil pump fitted (see thread), I am now experiencing some difficulty getting the inner races of the mains into position. I'm assuming that they have to be driven down until they are hard against the ground face on the flywheel. Is this correct? Stevens says it is better if they are a light drive fit on the mainshafts and I am aware that when the engine is stripped they should remain on the shaft, but how light is light? Mine seem to be quite tight on the shaft. I have supported the crank in the Workmate in such a way that I am only drifting against the relevant flywheel rather than the whole bottom end assembly, so hopefully I won't be knocking the flywheels out of true. The drive side one is nearly down, but the timing side is quite difficult.
 

Bill Thomas

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They are not very tight as a norm, It's easy to tip a bearing and think they are too tight,
Maybe bring it off and start again, If it has a steel cage, It's easy to damage them,
When using a puller,
The large part of the cage should be outer most, If it's inner most and you put a puller on it , The cage will be damaged, The brass cage type was better.
There should be a raised bit on the flywheel, About 30 thou that the bearing touches, Some times it is worn, And that will affect getting the rods in the centre of the cylinders,
If it is too worn, You can buy a shim, It's the same shim that's used in the Twin gearbox.
 

stu spalding

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VOC Member
Make sure that the timing side bearing is shimmed out enough for the oil pump worm to trap it, ie the worm should be tight against the bearing, not the step in the shaft. This is best checked with a dummy inner race that has been lightly honed to a slip fit. Cheers, Stu.
 

greg brillus

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Heat the inner roller race with an electric heat gun (like a hair dryer) with the bearing hanging on a punch held in a vice, then using some long nose pliers slip the bearing over the mainshaft and it should slip fully home very easily. You can use this method to remove bearings too although it will take some heating as the shaft will soak up some of the heat........saves any mechanical damage to the bearing.
 

Martyn Goodwin

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Heat the inner roller race with an electric heat gun (like a hair dryer) with the bearing hanging on a punch held in a vice, then using some long nose pliers slip the bearing over the mainshaft and it should slip fully home very easily. You can use this method to remove bearings too although it will take some heating as the shaft will soak up some of the heat........saves any mechanical damage to the bearing.
The late Mr Binns advised that the easiest method to install them was to heat them in a pan of oil (old saucepan on the stove, bearing in the engine oil in the pan till the oil just starts to smoke) then lift the bearing out of the oil with long nose pliers and drop it into the shaft. Straight way put a sloppy for box spanner over the shaft with a weight as a press onto the top of the bearing centre to prevent any creep as the bearing cools.

BUT before you do that on the Drive side you must first determine what if any thickness shim you need between the bearing inner and the flywheel in order to centralise the conrod. See OVR edition 18 - in the OVR Archives
 

Bill Thomas

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VOC Member
Are your mainshafts new ?, If so check the size, If old and marked, Clean up with wet and dry.
Always check New Parts some are not spot on !!.
Knock on with a tube rather that a punch, In case it tips.
 
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