30 replies to this topic

[poohbah]

Hi All,

 

I am rebuilding a 1275, originally from a MG Metro Turbo.  The crank is marked AM6232 and the centre main cap is marked 12G1430.

 

I am getting zero end float on the crankshaft with loose fitting, but I am getting the crankshaft seizing/binding when the centre main cap is tightened finger tight.  It turns freely with the upper thrust washers in place and without the centre main cap, but with the front and rear caps tightened.  It's only binding once I add the centre main cap.

 

The crank journals are measured, using a micrometer, to be perfectly round and the correct diameter.  I am rebuilding with ACL standard 1275 main bearings and ACL standard 1275 thrust washers.

 

Is this an issue with the thrust washers being too tight, hence the zero float?  Or can anyone shed any light on this please?

 

Cheers.

 

[KTS]

does it bind with the centre cap fitted, but no thrusts ?

[poohbah]

I’ve just checked and yes it does.

[Gaz66]

I would put my money on the wrong cap but....is the centre main journal the same size as the other 2?
Have you tried a different pair of shells?

[KTS]

If you have a DTI it might be worth checking how much run out there is on the centre journal

[poohbah]

I would put my money on the wrong cap but....is the centre main journal the same size as the other 2?
Have you tried a different pair of shells?

Thank you for the pointers.  I will try different shells tomorrow.  I will also double check the main journal sizes.  I dismantled this engine, so I know that it was turning by hand with the crank and caps in place, and I know it is the centre main cap which came off the engine.  I'll see if I still have the shells which came off to check to see if they're standard.

[poohbah]

If you have a DTI it might be worth checking how much run out there is on the centre journal

Thanks for this.  I do have a DTI so I will check this, hopefully tomorrow.

[poohbah]

 

I would put my money on the wrong cap but....is the centre main journal the same size as the other 2?
Have you tried a different pair of shells?

Thank you for the pointers.  I will try different shells tomorrow.  I will also double check the main journal sizes.  I dismantled this engine, so I know that it was turning by hand with the crank and caps in place, and I know it is the centre main cap which came off the engine.  I'll see if I still have the shells which came off to check to see if they're standard.

 

 

I'm measuring 50.83 mm for the front main journal, 50.83 mm for the rear main journal and 50.838 mm for the centre main journal.  So they're all within the 50.83 to 50.84 mm (2.0012 to 2.0017 in) that they should be.

[nicklouse]

Center cap the right way around?

[Spider]

Center cap the right way around?

 

^ This was my first thought, my next is what condition are the hollow dowels in ?

[jonlad]

Center cap the right way around?

 

I made just this mistake recently and the crank was binding

[poohbah]

Center cap the right way around?

I believe so.  The lettering on the top is in the same orientation as the lettering on the other caps.

[poohbah]

 

Center cap the right way around?

 

^ This was my first thought, my next is what condition are the hollow dowels in ?

 

There are a couple of nicks on them where they were gripped to pull them out, prior to machining the block.

[GraemeC]

 

Center cap the right way around?

I believe so.  The lettering on the top is in the same orientation as the lettering on the other caps.

 

 

I wouldn't rely on that.  The cap should be placed such that the tangs on the bearing shells go together on the same side of the crank

[mini13]

Ive had trouble with the dowels before, I now use the aftermarket billet ones from swiftune as a matter of course, Kad have also started doing them, but not used those yet

 

 

 

 

Center cap the right way around?

 

^ This was my first thought, my next is what condition are the hollow dowels in ?

 

There are a couple of nicks on them where they were gripped to pull them out, prior to machining the block.