Mondial piston ring composition and Flex-hone recommendation

Road-race engines and ancillaries - general discussion
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manoa matt
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Joined: August 11th, 2009, 11:18 pm

Mondial piston ring composition and Flex-hone recommendation

Post by manoa matt » October 28th, 2010, 12:06 am

Aloha Guy,

I recently purchased a set of Mondial pistons with 4.5mm domes for my 1978 Fiat 124 spider. The pistons will be installed in a 2L I'm prepping myself. The block has already been bored to the size of the pistons by my machinist, however I will be performing the fitting of the pistons, gapping the rings, and would like to flex-hone the bores prior to fitting the pistons. The rings do not look like "standard" Fiat Mondial piston rings.

The first picture is of the top and middle ring and the markings on the top surface of the rings.
The second picture shows the side profile of the top ring and the stepped profile of the middle ring.
The third picture shows the piston and oil control ring.

My questions are: What grade/grit of flex hone to use with these rings? What end gaps to run on the top and middle ring? Does the oil control ring need to be gapped, and if so to what specification?

Your thoughts and comments on the matter are greatly appreciated.

Thanks,

Matt Scarton
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Last edited by manoa matt on October 29th, 2010, 6:08 am, edited 9 times in total.

manoa matt
Posts: 9
Joined: August 11th, 2009, 11:18 pm

Re: Mondial piston ring composition and Flex-hone recommenda

Post by manoa matt » October 29th, 2010, 9:37 am

Eureka! Pictures are up and working.

Guy Croft
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Re: Mondial piston ring composition and Flex-hone recommenda

Post by Guy Croft » October 29th, 2010, 10:26 am

The black region on the outer face of the top rings suggests that they are molybdenum coated or inlaid and the Flex-Hone grade to use is 240 grade. They are certainly not chrome plated like some other OE rings were - chrome uses 180 grade whereas moly and plain cast iron, require 240.

Have a read of the attached too,

G
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Race piston & rings.doc
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manoa matt
Posts: 9
Joined: August 11th, 2009, 11:18 pm

Re: Mondial piston ring composition and Flex-hone recommenda

Post by manoa matt » October 30th, 2010, 12:29 am

Guy,

Thanks for the comments and advice on the rings, much appreciated. I figured out the photo posting with the help of a friend, sorry about the picture links.

thanks again, or as we say here "Mahalo"

Aloha,

Matt Scarton

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