Used cylinder surface finish measured

[reclino]

Took cylinder to a friend's shop and borrowed his PocketSurfIII and measured surface finish of the bore. The area not worn by the rings measures 6 Ra and the worn part measures 4 Ra. This is after scrubbing the bore with hot soapy water and Scotchbrite pad.
I am wondering if this is too smooth for the new Total Seal rings to bed in.

[Trackrash]

I think this is a subject that needs to be explored. Perhaps those that are the experts can provide a table as to what ra is optimal for each type/brand of ring when used in nikasil coated cylinders. It seems there are different recommendations according to the rings used.

I will tell you that my used and scotch-brited Mahle nikasils using the JE suplied Goetz rings seemed to take forever to totally seat, like 500 miles, but all is good after about 5k miles so far.

Have you seen this thread? Lots of discussion. cylinder finish issues

[r lane]

Having read an article on rings, and it was general as can't apply to all, but the thrust was that the quality of ring material and design improvement over the years is requiring a much less textured cylinder surface. The rings not only don't need to be scuffed up as much by a highly textured hatch in the cylinder, but a quality ring also has flexibility to follow the cylinder wall distortions that happen under load. I raced in the 70-80s and used a Sunnen hone for my cylinders. Was amazed at the grit they wanted me to use, appeared as one had taken a brick to the cylinder walls. Not so much anymore.

[Glenfield]

Wholeheartedly agree, Tracktrash. Was trying to track this down everywhere on Pelican. Seems earlier threads / experts that established the 6RA spec used Goetz rings. There was a post that I might be able to track down where one gentleman went through 3 top ends to find a ring that would seat with re-plated cylinders!


I’m using Mahle rings on a current rebuild with re-Nik’d cylinders and so will have that beta soon enough.

[reclino]

I had a discussion with a well know Porsche engine builder and he suggested sending my second rings back to Total Seal and have them cut to Napier profile. This improves oil scraping ability of the ring.
I bought the rings almost 4 years ago, and have had them on the shelf that long. Called Total Seal and after a quick discussion, they said it's no.problem, send them back we will cut them for $9.50 each. Need to get them boxed up tonight.