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MG MGA - Crank Thrust Washers


I noticed that when I press the clutch pedal to do a gear change, the engine idle drops so low that, if I don't change gear quick, the engine dies completely. This seems to happen when the engine is at full operating temperature. Some months ago when I had the engine out, I replaced the crank thrust washers with a std set. The old set were also std but the bottom two were fitted the wrong way round. This was a problem I had before replacing the washers, but I learned to live with it and I don't remember the engine dying out completely, only a noticeable reduction of the idling speed. A local mechanic informed me that most probably the crank is braking because the thrusts need to bed in properly, and this would take a couple of thousand miles or so to take effect. Any comments on this? Should I just ignore the whole thing for the next few months and see what happens?
F Camilleri

Do you have a carbon operating bearing or the roller/ball bearing type for the clutch?
Please describe how you fitted the thrust washers as early Workshop Manuals are incorrect.
Which way were the oil grooves in the thrust washers facing?

M F Anderson

Yup. If you install the thrust washers the way the Workshop Manual describes, you're screwed, because the book is wrong. See here:
By the time this CSM was published MGA were already out of production. I don't think there was any follow-up revision of the Workshop Manual showing the correct information.

Assuming you do have the thrust washers in the right way around, the slow down of idle speed is (always in my experience) attributable to poor tuning of the carburetors, commonly one too rich and the other too lean (or sometimes both too lean). See here:

Solution is, give it a good tune-up.
Barney Gaylord

Barney -
My "Final Edition" of the MGA WSM AKD600D is correct. Title page "Issue 5. 40954"
Relevant page "Issue 3. 20290"

Also my early MGB WSM AKD3259C is correct.
Title page not numbered
Relevant page A16 not numbered for issue, but continued on A17 "Issue 3 60230" The critical wording being on A17 with the correct illustration overleaf on A18.

FR Millmore

Hi Mick,

I have a carbon type clutch bearing which, together with new pressure plate and new clutch driven plate were all installed at the same time as I replaced the trust washers. These washers were installed with their oil groves facing the crankshaft, which I am pretty sure it's the right way to go.
Barney, thanks for input to this thread. As always very informative and your advice is easy to follow. I wouldn't think that the engine tuning is out much, but if you're saying that even being slightly off tune could make all the difference, then I shall most certainly give the engine a very critical go over to try and get both the ignition timing and the carbs tuning spot on.

F Camilleri

This thread was discussed on 22/05/2011

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