14 replies to this topic

[tom1]

HI , just took my crank out to find my thrust bearings looking like this

 

 

 

A short history. I build the engine with a friend  (who is a professional engine builder), lots a of years ago. It has not done more than 700 road miles. I never had any faith in but was unsure why, it was a oil pressure thing, slow for the oil light to go out but it was set a 22Lbs. The crank was sold to me as a Cooper S,is it ? On the center jornal it says + 0.003, the thrust  bearings say STD. We must of checked the end float ! What do you think we got wrong all those years ago ?

[Vipernoir]

Wrong endfloat leading to lunched bearings I'd say.

 

You'll need to take the crank to a machine shop and get it checked.  If it really was +.003" to start with, you may need to go to +.030" if it has damaged the thrust face.

[Ethel]

Any numbers on the other side? Obviously they'll be 1-5/8" big ends. The wear looks fairly even on all 4, so not likely to be a badly set up clutch. Doesn't look to be much sign of heat either?

[ACDodd]

What clutch have you got fitted?

Ac

[Vipernoir]

If it was a super-heavy clutch, wouldn't the thrusts only wear on one side ?

[Stevie W]

Hi,

Oil pressure thats slow to build up won't have helped your thrust washers, especially if the clutch was actuated with low oil pressure after initial start-up!

Cheers, Steve.

[tom1]

I think having just looked at the flywheel assembly it is a orage pressure plate with a six pieces of sintered, not a full paddle plate clutch.

[carbon]

Tom,

 

Is the engine using a S block or a 'std' 1275 block?

 

There is a slight difference between the centre main bearing widths between the two. If you use an S crank in a 'std' block then the thrust bearings will not be standard width.

[tom1]

As far as I know it is a standard block.

[ACDodd]

If the end float was very likely incorrect i would look at the setup of the diaphragm. See Miniworld last month for an article on how to set these up.

 

AC

[MIGLIACARS]

check big ends to see if its a cooper s or gt crank

[tom1]

check big ends to see if its a cooper s or gt crank

Please specify what I need to check/measure? What is the difference between cooper s & gt crank ? Thanks Tom

[MIGLIACARS]

the size of the big end journals

 

cooper s 1.625"

 

gt and A plus  1,75" 

[Cooperman]

That is a very unusual wear pattern. With thrust bearings the main wear is on the clutch, i.e. the thrust applied, side. That is why a Mini engine should never be started with the clutch pushed down as that puts full clutch spring load straight onto the face of the thrust bearings during the period of zero to low oil pressure immediately after firing up. The centre main oil feed is feeding the centre main bearing, two sets of big ends and a pair of thrust bearings.

However, wear like this on both thrust & non-thrust sides would indicate that the bearings were set too tight in the first place.

After checking the thrust faces and all journals, when re-building measure the installed end-float with new bearings and set up to achieve end float of 0.0015" to 0.004".

Assuming that is an 'S' crank with 1.625" nominal dia. big ends in an 'S' block it is straightforward. But if it is an 'S' crank in a non-'S' block, the different main journal widths will require specially machined down +0.030" thrust bearings to achieve the correct end-float.

As with all engine building, measure, measure then measure again.

[tom1]

Yes, it is  non S block so I will have to get some thrust bearing machined down.