<html><body><div><div>I rebuilt my engine in October, 2020 and I got my pistons from Austin Healey Spares in the UK. They were 0.060 over M spec pistons and as you can see from the photo, they did indeed need the fifth ring. Hope this helps with your situation and thoughts. <br></div><div><br></div><div>The pistons I replaced weren't even AH pistons. My machine shop couldn't figure out where they originated, but the replacement rings we found for them that would fit were for a 1950's Plymouth or Mercury. They were also flat topped and were going to create too much compression, so that's why I went with the M spec pistons.<br></div><div>Steven Kingsbury<br></div><div>BN1</div><div><br></div><div><img style="max-width:100%" src="cid:36d41c1f-19ac-416b-8ec9-06173dcbe203@icloud.com" > <br></div><div><br></div><blockquote type="cite"><div>On Apr 29, 2022, at 6:23 AM, S and T Miller via Healeys <healeys@autox.team.net> wrote:<br></div><div><br></div><div><br></div><div><div style="font-family: inherit; font-size: inherit; color: inherit;">Hoping to validate my decision before buttoning things up on my 100 engine. Ordered .020 over standard (not 100M) piston set from Moss. Piston is a 4 ring piston, but came with 5 rings.
They were identified where each ring should be fitted #1-5, with #4 (3 piece oil control ring), and #5 (one piece oil control ring). Obviously not a groove for #5. Ring set was marked 100/100M, so I'm assuming they send the same set for both and you just leave
off the #5 (one piece oil control ring) on the 100 pistons. This is what I decided to do. Now Moss's 4 ring set on the website shows the three upper rings and the #4 ring being the 3 piece oil control ring reinforcing the thought that the #5 (one piece ring)
should be disregarded. <br></div><div style="font-family: inherit; font-size: inherit; color: inherit;"><br></div><div style="font-family: inherit; font-size: inherit; color: inherit;">Called Moss Tech support and after a week they got back to me and said that he didn't know the answer, and they would get back to me. That was another week ago and still no answer. Also
nothing is indicated in the piston directions. Thought I would check to see if anyone on the list ran across this?<br></div><div style="font-family: inherit; font-size: inherit; color: inherit;">TY, Shawn<br></div><div><br></div><div><div>The Millers<br></div><div> <br></div><div> "Always drive them, but remember each drive in an antique car is a test drive."<br></div></div><div><div>_______________________________________________<br></div><div>Support Team.Net http://www.team.net/donate.html<br></div><div>Suggested annual donation $12.75<br></div><div><br></div><div>Archive: http://www.team.net/pipermail/healeys http://autox.team.net/archive/healeys<br></div><div><br></div><div>Healeys@autox.team.net<br></div><div>http://autox.team.net/mailman/listinfo/healeys<br></div><div><br></div><div>Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/airtightproductions@icloud.com<br></div></div></div></blockquote></div><div><br></div></body></html>