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TS Crank Thrust Bearings...advice needed

After a long haul, I finally got her stripped down today. Clutch pedal judder was initially diagnosed as clutch thrust bearing and that was replaced at considerable effort and expence. Didn't however fix the problem.

Next place to look was the crank thrust bearings. PM to Smaky and a point in the right direction.... finally got them bladdy hidden sump bolts out.

Happy to find a thrust bearing (bottom on image) lying in the sump. I say happy becuase at this point I was starting to think of a whole heap of expensive jobs if this didn't fix her.
The bearing is clearly scored but still relatively thich and evenly worn.


For the life of me, I couldnt see any other bearings.
Looked ont tinternet and every picture seemed to show 4 half moon bearings.

Starting to panic at this stage..... where are they.... is this a complete strip down to find them mangled in the oil pump....?

Had another look where they should be... an could just about make out a chewed up piece way up. Levered the crank across a bit and was able to persuade it out with a flat piece of hacksaw blade.... the only thing I could see thin and stiff enough to prod.

This side was a lot more worn than the other as you can see from the other pics.

http://i634.photobucket.com/albums/u.../Photo0633.jpg
http://i634.photobucket.com/albums/u.../Photo0634.jpg
http://i634.photobucket.com/albums/u.../Photo0635.jpg

The advice I need is.... do I fit standard replacement bearings or do I fit oversize?
Whats the difference in thickness between the 2?
The crank/bearing surface on the less chewed bearing is perfectly smooth and even. This is at the timing belt side.

The other side (near the flywheel) is smooth as well..... only it has what looks like a machined slight recess that the bearing could partly seat in. Would that indicate the crank has been ground in the past? Is that normal on a factory standard crank?

Becuase the bearings are so worn, I cannot get an idea of part number or thickness.

"If it can't be fixed with a hammer, your problems electrical!"
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never done this on an alfa but have on plenty of other engines. triumphs were famous for spitting the thrust bearings out.
if the crank thrust bearing surfaces have not been reground, then a set of standard size thrust bearings should do the job. get a micrometer and measure the thicknesss of the mangled bearings and replace with the same size. (or closest size up taking into account wear)
now check that the crankshaft endfloat is within tolerance, lever the crank back and forth and try to measure the end float with feeler gauges. or better still a DTI
If it's out of tolerance (too much endfloat) you need to get the next size up bearing and if necessary file the back until it is the required thickness.

If there is excessive wear/damage on the crank thrust faces then the crank will have to be machined.

99% of the time you can get by with just fitting replacement thrust bearings. so keep smiling

Whats the mileage?
clutch felt funny because you were trying to push the crankshaft through the front of the engine.
Maybe a previous owner riding the clutch all the time..

Last edited by seadart; 11-11-10 at 12:50.
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You need to measure the endplay and see if you can get a suitable size thrust bearing. You have to be careful that the surfaces for the bearings are smooth and true. As you've gone this far you should really pull the caps and inspect your main and big end bearings (keep all the caps in the same place and orientation).
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reading your post again you say that there is what appears to me a 'machined recess' in the block??
take care because with no thrust bearing, this could have been 'machined' by the crankshaft every time you de-clutched
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I have a crank and block in the garage i'll try and take a piccy tonight.
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Hunting everywhere... getting to the point of petrol + swan vestas....= car fixed.

What is considered acceptable endfloat for the crank?
When I order the new thrust bearings, do I quote size needed, and if so, do they work in metric or ye olde thou's?
I need to get the bearings ordered and sorted as I've been using my brothers car for over 3 weeks now.
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Quote:
Originally Posted by Prof Peach View Post
Hunting everywhere... getting to the point of petrol + swan vestas....= car fixed.

What is considered acceptable endfloat for the crank?
When I order the new thrust bearings, do I quote size needed, and if so, do they work in metric or ye olde thou's?
I need to get the bearings ordered and sorted as I've been using my brothers car for over 3 weeks now.
You have to go to technical data in the manual for available thicknesses and acceptable endfloat.

Being Italian they are prob. measured in Napoleon.

I always used to buy thrust washers in standard and oversise so's I had something to play with.. they are quite cheap, and I see on another thread there's some confusion over the oilways.. they face the crankshaft. Keep smiling.
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Just spoken to stealers. Available in standard and +0.127.....
Genius.... but he cant tell me how thick standard ones are.

He did however give me an endfloat figure of between 0.080 + 0.265 (metric..?)

Does that sound reasonable?
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Just to repeat my PM, for the assistance of others, half-thrust bearings are:

Standard: 2.342-2.358mm
Oversize: +0.127mm

Crankshaft end-float should be between 0.059mm and 0.221mm.

These figures are from a 145 manual (which details AR67204 and AR32301 engines), so I'm guessing they may refer to the CF1/CF2 engines (I never can remember which are which!). I can't see later ones being much different though...
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Quote:
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Just spoken to stealers. Available in standard and +0.127.....
Genius.... but he cant tell me how thick standard ones are.

He did however give me an endfloat figure of between 0.080 + 0.265 (metric..?)

Does that sound reasonable?
Its got to be metric.. 265 thousandths of an inch is over a quarter of an inch!!
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Appreciate the input fella's. Think I need a new crank.
I'm off now to kick the cat.
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I'm off now to kick the cat.
Best thing for them!
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By my reckoning I have 0.57mm (0.0224") gap with oversize bearings in place. With everything in situ, oiled and running, will that translate to 0.57 endfloat, or will the film of oil or any other factor change that figure for endfloat?

As you can tell, I'm getting desperate now. Gonna fit oversize and see how she goes. Cant imagine anything will implode with 1/4mm too much movement.
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Quote:
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By my reckoning I have 0.57mm (0.0224") gap with oversize bearings in place. With everything in situ, oiled and running, will that translate to 0.57 endfloat, or will the film of oil or any other factor change that figure for endfloat?

As you can tell, I'm getting desperate now. Gonna fit oversize and see how she goes. Cant imagine anything will implode with 1/4mm too much movement.
Your arithmatic seems ok. but you need to trial fit and measure to be sure..there's always a wee bit of difference.

That seems to be about double the max tolerance, apart from issues related to conrods etc, the crankshaft lashing about that much could allow one thrust washer to fall out after a bit of wear, if one falls out the other soon follows meaning back to square one.

Theres a way of making the thickest washer thicker!! its an old engine builders trick so its down to your fitting skills. using brass countersunk rivets, four equidistantly placed, rivet two
thrust bearings together, back to back and file for the correct thickness..

A better way is to make your own thrust washers out of phospher bronze. Again its down to your fitting skills, used to be used to salvage a block that had lost metal on the thrust faces. On race engines we used to pin them in place using brass dowels about 4mm thick. got to take the crank out to do that though.

Or if its the crank thats lost metal get a new crank.. go give the cat another kick.

Has the crankshaft ground into the main bearing cap that retains the washers??

Just noticed you live in hampshire so do I, do you have access to a bench, vice??

Last edited by seadart; 12-11-10 at 20:30.
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Quote:
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Has the crankshaft ground into the main bearing cap that retains the washers??
No... I don't think so.
The bearing that dropped out is the belt end side.
The one that was still in but a bit chewed up was on the Crank side. Thats the one that takes the thrust from the clutch.

Looking at the bearing, it looks like it was worn down, over heated and slightly dislodged. But it was at least stopping the crank from hitting the bottom end.

It looks to me like the crank has been ground in the past (it was a recon engine 2 years ago - fitted by AutoItalia)

I'm gonna see how it looks with oversize fitted. Just wondered if that estimated gap with new bearings fitted would give me the endfloat figure.
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I have a crank and block in the garage i'll try and take a piccy tonight.
Any chance of those piccys Biffa?? I'm going off memory of ancient Jags and suchlike.
Thrust bearings a thrust bearing!!
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No... I don't think so.
The bearing that dropped out is the belt end side.
The one that was still in but a bit chewed up was on the Crank side. Thats the one that takes the thrust from the clutch.

Looking at the bearing, it looks like it was worn down, over heated and slightly dislodged. But it was at least stopping the crank from hitting the bottom end.

It looks to me like the crank has been ground in the past (it was a recon engine 2 years ago - fitted by AutoItalia)

I'm gonna see how it looks with oversize fitted. Just wondered if that estimated gap with new bearings fitted would give me the endfloat figure.
Thats good news..
The front one allways drops out first, you caught it just in time, the real damage occurs when the back one falls out and then when you de-clutch you force the crank against the casting and start removing metal at an alarming rate. the excessive endfoat with oe oversize bearings is a bit odd though. I'll do those sums of yours and get back...
Is there not a bit on the old bearings that you can get a vernier on to measure the thickness??

keep smiling and kicking..

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Have you tried fitting the bearings yet? 0.5mm is up to 10x too much float...
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OK.. From the figures quoted above

Standard bearing optimum is 2.35mm
Oversize bearing optimum is 2.477mm (2.5mm as near as dammit)
End float specified MAXIMUM is 0.265mm
Your end float with oversize bearings is 0.57mm

Which is...... 0.305mm too much.

.

Which means that when you start up and depress the clutch it is highly likley that the front bearing will fall out.. when you release the clutch the crank will move back and rear bearing will fall out. (you are very lucky that the rear bearing was still hanging in there).. no harm in trying it though if you want to .

start up.. rev.. depress the clutch and keep it there if you feel and hear a jolt through the clutch switch off immediatley.. take sump off..

I've got a feeling that your crank's thrust faces have each been overground approx 0.150mm, (which co-incidentally is exactly the difference between the standard bearing thickness and the oversize bearing thickness.. Possibly, when the crank grinder did his sums he forgot to divide by two!). And that's why the bearings are in the sump.

Someone check these figures..

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I'm in work now i'll try and get piccys upload in the morning...
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Quote:
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Which means that the end float is more than twice the thickness of one bearing.

Someone check these figures..
The bearings are about 2.5mm so the endfloat is nowhere near the thickness of a bearing.

Been under the car measuring again as all the figures are doin me ed in.
These figures are as accurate as I can get with feelers and micrometer.
Using The 2 existing bearings and measured the gap left when all is tight.

Combined existing bearings: 4.572mm
Clear gap: 0.90mm
Total space for bearings and gap: 5.472mm

New bearings (pair oversized): 4.954mm
Those new bearings fitted will leave 0.518mm clearance

Endfloat figure from Alfa dealer: 0.080mm - 0.265mm
That would give an excess endfloat of 0.253mm

Is that going to destroy the engine??

I've just had a text from a mechanic and they work to a max of 0.5mm before any work would be done, but everyone else seems to point to a much smaller gap.
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Found these on one of my other posts,
Old thrust washers
New Thrust washers
newly ground crank
block without washers
crank
crank pre grind
cool pic of the bore

i think i need to take a pic of the side of the main journal/
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Cheers Biffa. Unfortunately I'm doing mine in the car....
lying on my back...
freezing my plums off.

NO-ONE needs to see pictures of that.
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The bearings are about 2.5mm so the endfloat is nowhere near the thickness of a bearing.

Been under the car measuring again as all the figures are doin me ed in.
These figures are as accurate as I can get with feelers and micrometer.
Using The 2 existing bearings and measured the gap left when all is tight.

Combined existing bearings: 4.572mm
Clear gap: 0.90mm
Total space for bearings and gap: 5.472mm

New bearings (pair oversized): 4.954mm
Those new bearings fitted will leave 0.518mm clearance

Endfloat figure from Alfa dealer: 0.080mm - 0.265mm
That would give an excess endfloat of 0.253mm

Is that going to destroy the engine??

I've just had a text from a mechanic and they work to a max of 0.5mm before any work would be done, but everyone else seems to point to a much smaller gap.
Yep you are right ..sorry tired, your figures look good.

I think if you start the engine they will stay in.. but right on the edge of tolerance. If you suspect they have fallen out again for christs sake switch off and dont press the clutch.
Shouldnt destroy the engine straight away, if they fall out they will cause metal to metal contact between crank and block eventually causing major damage, I'd get some thicker bearings made up. or get onto a bearing supplier. I know youre freezing your conkers off but make absolutly sure you have no damage here.

Ses me sitting in a nice warm office looking at Biffas nice shiney photo on a computer.. really stings when you get dirty oil in yer eye doesnt it??
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