Bearing shell condition

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dudload
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Bearing shell condition

Post by dudload »

Afternoon all,

Still trying to get to the bottom of the knock/rattle at certain revs I dropped the sump and took the first two bearings out, until I had to stop yesterday as it was just too hot!

The bearings are marked as 0.02 oversize, which corresponds to the crank journal measuring 1.605-1.610 on both.

I'll try and get out later today, but what's the verdict on these shells?[attachment=0]20220617_160600.jpg[/attachment
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dudload
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Re: Bearing shell condition

Post by dudload »

Well, I think I've found the issue, centre main looks like below. Assume this is a crank regrind given the condition?
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dudload
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Re: Bearing shell condition

Post by dudload »

Just checked the clearance on the centre main and it's 0.050mm, so within tolerance. Question is, will new shells do it, or is it regrind time?
philthehill
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Re: Bearing shell condition

Post by philthehill »

Your crankshaft centre journal do not look too bad even though the shell is worn down to the copper backing. Therefore I would replace all the shells and see how it goes. I have seen worse shells than that shown above which have been replaced with new shells and the engine ran satisfactorily with no knocking or other problems.
You could strip it all down and go to the expense of having another regrind but to me doing the above would be my first step.
If you feel so inclined - you could remove the crankshaft and measure the centre main journal to ensure that the journal is round and of the correct size before purchasing new shells or undertaking a re-grind.
Good luck.

dudload
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Re: Bearing shell condition

Post by dudload »

Thanks Phil - two questions, what's the best way of getting the centre main top shell out?

Working under the car on the road, so space is at a premium! Which leads to the second question (as working on it engine-in), is it ok to replace main shells when front and rear could be just as worn?
philthehill
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Re: Bearing shell condition

Post by philthehill »

Wind the shell out of the block seat by turning the crankshaft. Carefully use a flat screw driver to give the shell a push to start it moving. The shell should come out without any difficulty as the crank journal is not held tight by the cap/shell. To fit the new top shell - wind the new well lubricated (white metal face of the shell) into the block.
Wind the shell so that the tang of the shell is pushed out of its notch. When the top shell has been rotated 180 degrees the shell will just drop out.
As regards front and rear main bearings - I would gamble that they are alright and I would just replace the two centre main shells.

dudload
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Re: Bearing shell condition

Post by dudload »

Thanks again Phil, got the new shells on order (current ones are all .020 over)

Suspect the front and rear are worn-ish as the oil pressure drops to about 15psi at idle, although the pressure light never comes on. Hopefully replacing the main will improve that a bit though!

Given the state of the mains, do you reckon the rattle at about 2-3k revs could be down to that?
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Bill_qaz
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Re: Bearing shell condition

Post by Bill_qaz »

I know it could be just camera angle but space between thrust washer and crank looks large, have you checked crank end float? If excessive it can starve centre main of oil pressure leading to wear.
Regards Bill
philthehill
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Re: Bearing shell condition

Post by philthehill »

All you can do without fully stripping the engine is replace the centre main bearings and see what happens.
If the oil pressure light was not coming on with the centre main bearing showing that much copper that is a good sign.
I think that the camera angle may be the problem in that the thrust washer gap appears to be larger than it should be.
It is well worth checking the crank end float clearance though. To check the clearance put a lever between the block and the crank web and try and move the crank in one direction (fore and aft) and then the other. If the clearance is excessive you will feel that excessive movement. The clearance should be 0.002" - 0.004".

dudload
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Re: Bearing shell condition

Post by dudload »

Ok, will do. Can't seem to find anything on float in the workshop manual - I take it I need to measure it with feeler gauges when the bearing cap is on?

(Where can you see the float on the picture I uploaded?)
philthehill
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Re: Bearing shell condition

Post by philthehill »

Whilst not clearly stated in the workshop manual AKD530 L it is specified as main bearing end clearance in the general data section of the APHM engine section. The quoted specification is carried through to the other 'A' Series engines as the clearance is generic throughout the 'A' Series range. The specified clearance is 0.002" - 0.003". I have quoted 0.002" - 0.004" which is acceptable.
To confirm the measurement the quoted 'Crankshaft End Float' for the 1098cc Marina engine (virtually the same as the 1098cc Minor engine) is 0.002" - 0.003 & taken from BL wksp man AKM4580.
The Marina wksp manual goes into far more engine detail than the Minor wksp manual and it is worth having a copy.
You should be able to get a good idea of the end float using the lever method I described above without having to resort to the use of feeler gauges or dial gauge.

dudload
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Re: Bearing shell condition

Post by dudload »

Thanks Phil, I've measured up the thrust washers that were in there (following the marina manual calling to check for wear) and looks like mine are quite significantly undersize . 0.078 Vs 0.090 (I believe!) and are also down to copper backing

I'll add some standard thrusts to my order.

In your method, assume it's with bearing caps all reinstalled? May as well use a feeler gauge given I've got a 0.003 one already
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philthehill
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Re: Bearing shell condition

Post by philthehill »

Whilst those thrust washers are worn they are not down to the bottom of the vertical oil slots. If they were down to the bottom of the vertical oil slots then those thrusts would be really worn.
You may already be aware that the vertical slots go towards the crankshaft web.
I would just replace the worn thrusts and see how it goes.
You should be able to get a feel for the end float with just the top half of the thrust washer installed.
The thrusts that I have are 2.3mm thick and are marked as 0.003" oversize thickness. I would advise that you check the back face of your thrusts for size before ordering.

dudload
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Re: Bearing shell condition

Post by dudload »

Thanks, just been out and measured and the clearance (with the current worn thrust washers) is 0.006.

Weirdly, there's no markings on the back, so have to asse they're standard size. Will order some standard from esm and see if that reduces the gap down to 0.004 max. Otherwise will then order some oversize ones if still not enough.

Amazing help as always
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Re: Bearing shell condition

Post by dudload »

I see that the +003 washers are out of stock everywhere. It's it ok to put one size on one side and standard on the other? Just thinking if clearance is still too large with new standards if I can buy 005 oversize and put on one side
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Re: Bearing shell condition

Post by oliver90owner »

Your current thrust bearings are dead. It would not be good practice to use thrust bearings in that state of wear. That obvious wear is causing at least some of the end-float excess.

You need to know how much white metal those have lost, to know which size of replacement is required. Fitting different sizes of good thrusters is OK.

If you decide to fit any that are worn out, fit the new to the front of the main bearing - as operating the clutch will most certainly be pushing the crank forwards.
dudload
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Re: Bearing shell condition

Post by dudload »

Thanks - certainly won't be using those thrust washers, all for replacing. Will buy the std and +005 just in case I need to mix and match if it's ok to do so!
philthehill
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Re: Bearing shell condition

Post by philthehill »

As above - you do not have to use the same thickness of thrust washer either side of the centre main. So long as both thrust washers are of the same thickness on the same side all will be well. Sometimes in the past I have used good serviceable S/H thrusts to obtain the correct end float.
Fit any new thrust washers to the rear of the block centre main (not front as stated above) because the crankshaft is moved forward when the clutch is depressed and the resulting thrust pressure is carried on the rear face of the block centre main not the front face of the block centre main. When the clutch pedal is depressed the loading on the front face of the block centre main is zero.
You can also adjust the thickness of the thrust washer by placing a fine piece of wet & dry on a piece of glass rubbing face up, spray the wet and dry with WD 40 and by rubbing the white metal side of the thrust washer on the wet & dry in a figure of eight motion the thrust washer white metal can be reduced to the required thickness. The figure of eight motion ensures that the rubbing face is kept true.
Just been looking in the Triumph 2000/2500 wksp manual and the crankshaft end float is 0.006" - 0.0014". So you have plenty of scope to get the 'A' Series crankshaft end float correct or near correct. :)

dudload
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Re: Bearing shell condition

Post by dudload »

Hi Phil,

Back at work and trying to get the top main bearing shell out with no success!

I've pushed it a little by the retaining tang side (i.e. tang sige disappears into engine) and turn the engine over with starting handle but nothing moves.

Am I missing something here?
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les
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Re: Bearing shell condition

Post by les »

I think you should be pushing the shell from the side opposite the tang, to avoid jamming.

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