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MG MGB Technical - Piston re-ringing

Hi Just gapping the new rings and getting on to the oil control rings - 3 piece Hepolite type that when the 'expander' ring is loosely fitted down the bore prior to fitting to piston it has a much obvious greater diameter.Is this correct such that when all assembled on the piston with the two scraper rings in place it will 'squish up'? Quickly putting my piston ring clamp on the control rings do not go flush with the side of the piston.

It could be Hepolite put the wrong bag of controls rings in the box but all the other packets are OK
Advice would be much appreciated
Mark

Mark Dollimore

I am sorry I cannot help with your question - but I am confident someone will. Could you tell me please which oil control rings you are using and where you sourced them please? wondering what line of thought took you down the oil control route.
regards, Graham
Graham Moore

Mark,

I can't give you a definitive answer, but I can tell you a few things I remember about the oil control ring, assuming yours is the type I am thinking of.

The tips of the expander must not overlap. They butt up, and the tips are different colors so you can look to see that they are not overlapped. Then the upper and lower rails have to sit in the recess of the expander so that they hold it all together.

Then, they do take some force with the ring compressor to get them to fit down the bores. So, it would not surprise me if the expander were larger than the bore when relaxed. It might get accordioned when installed, but I don't know that for a fact.

Charley
C R Huff

Mark That looks about right. I have used these rings many times and although they do take a bit of compressing you should not have a problem. One trick, after fitting the ring compressor and starting the piston in the bore, use a hammer handle on end to tap around the top of the compressor to seat it dead flat on the block. Then while still holding the compressor hard against the block tap the piston in with the hammer handle. Oil the ringa well before fitting. Denis
Denis4

Looks about right to me too, but if you want piece of mind try the top and bottom rails of the oil ring in the bore. If they overlap you have problems, if they have a gap then you know you are OK.

It looks like you are re-ringing old pistons? If so, the top groove looks unmachined. Have you checked the side clearance between ring and groove? The book says if you can get a 6 thou feeler in more than 1/16" then the grooves need attention one way or another.
Paul Walbran

And if I'm not mistaken, the ring land clearance that Paul is talking about is measured with the ring held in flush with the side of the piston. If the ring was hanging out you could stick anything in there.

Charley
C R Huff

Many thanks for your replies,
Graham - No train of thought the rings were as they came in the set of replacement Hepolite rings Part No R25566
Paul and Charley - Yes I am re-ringing used pistons the compression rings sit in the grooves with 2 thou side clearance and the scraper rings have a goodly gap when placed into the bore, the compression rings gap out at 12 thou so they are spot on.

Cheers

Mark
Mark Dollimore

This thread was discussed between 26/05/2014 and 27/05/2014

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