I know it's been discussed before, but I've forgotten. What exactly is the top groove for on an M20 piston? Ron

email (option): ronpier@talk21.com

I read it's a 'heat dam' to limit the transmission of combustion heat to the top ring...Ian

email (option): ian@wright52.plus.com

Thanks Ian:+1: Ron

email (option): ronpier@talk21.com

I have heard some used this groove to put in an extra oil ring. Slightly widened.

Yes Michael. I've also heard of a top ring being fitted. But I just couldn't remember what it was really for.....The heat barrier makes sense.
Definitely only 3 rings shown in the parts lists.

Ron

email (option): ronpier@talk21.com

Yes, I thought it was used as a heat barrier, taking the heat from the top compression ring. How was that gasket for the tilly Ron? I hope it was all good and you don't have any more problems.

Regards TTJohn

email (option): Jomichael@aol.com

Yes John your gasket is fitted. But held up with the water pump which was refurbed????? and leaked badly before the engine was even started. I stripped it myself to find that nothing has been touched. The firm wont admit anything but have refunded my £120 in full and hoping to collect it from John Walker at Netley on Friday who has hopefully done a proper job. Ron

Pictures tell a thousand words.

email (option): ronpier@talk21.com

Looks good on there mate, What size is the mechanical seal in the water pump, I still have one or two from my days as a catering engineer, I think they are 19mm 22mm O D ceramic, shaft size was about 1/2" I think.

Regards John

email (option): Jomichael@aol.com

You are probably right with those dimensions John! But I didn't measure anything when I stripped it, so relying on John Walker and his engineer. Cheers Ron

email (option): ronpier@talk21.com