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MG MG Y Type - Piston Removal Procedure

According to the maintenance manual for the XPAG engine the pistons and connecting rod can be removed with the engine block in place. They are removed in a downward direction adjusting the crankshaft for clearance. Once they are removed, decarbonied and the reings replace and clocked they can be reinserated from the bottom in a reverse manner. My question is how do you compress the new rings when inserting them back into the engine block?
E. Geissler

Use a piston ring compressor Ed - same as if you were coming in from the top.

Have you deglazed the sides of the cylinders? Have you checked for wear and wall damage? Are you sure the new rings will be appropriately sized? It is an awful lot easier to do all this work from the top with the head off though.
Paul Barrow

Yes, it can be done this way though it is a bit nerve wracking avoiding jamming as you have to turn the crank as you move the piston down. This can be more difficult with larger pistons in an overbored block. I have done it in an emergency when time was short but agree with Paul that the head needs to come off to do the job properly.
Ian
ian thomson

Thanks Paul and Ian

The head has been removed. What can I use to deglaze the cylinders? There appears to be no damage to the walls. I am working with Moss to ensure the proper rings will be purchased.

Regarding fitting the new rings, it has been suggested by members from other clubs that once the pistons have been removed from the bottom, old rings removed and the pistons cleaned they can be inserter back from the botton until the groves are just visiable at the top of the block. The new rings can be insalled and a piston ring compressor utlized to move the pistons back into the cylinder.

Any thoughts?
E. Geissler

Check the ring gap on ALL rings as I had to set the gaps because all of them where WRONG.
Bob Wood

I do agree Bob. You have to gap the rings carefully as there is no guarantee that they will be accurate out of the box. Unfortunately I have often found the gaps to be too wide as supplied. This could be due to a worn bore but I would expect good quality rings to be oversize to allow for this. Pay careful attention to the tapering of the bore also as although it may be worn at the top it will probably have little or no wear at the bottom so check the gap at both extremes. Another check to do is the side clearance of the rings in the grooves. I try to keep this to a minimum, which often means replacing pistons which are otherwise good as obtaining oversize rings can be difficult and probably not economic. You will find as many specs as people you ask, or books you read, so all you can do is your best.
Ian
ian thomson

Ed

You will need a "honing" tool I beleive. (https://duckduckgo.com/?t=ffab&q=deglazing+cylinde+hone&atb=v359-1&ia=web)

Be careful not to remove too much material. I have never done this - always used a quality machine shop personally. No idea how you use them or which one would be best.

Paul

Paul Barrow

This thread was discussed between 11/02/2024 and 16/02/2024

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