Piston ring scuffing

[Dave Mann]

The engines we built 4000 to 18000 BHP if the piston rings were replaced the cylinder HAD to be honed followed by a 16 hour run in starting with 30 minutes at no load rising to full speed, the run in could be halved by using BP running in compound added to the fuel. I often wonder what happened to the 2000 gallons of fuel and running in compound when the works closed and was demolished.

[Hugh Barnes]

Do I count 9 cylinders in vew, presumably making it an 18 cylinder engine. Is that an odd number or something that relates to a specific application?

[Colin Cooke]

Hi All,

Enjoying this thread, as I'm currently in the process of choosing pistons for an engine build. I have a few questions:

Firstly, what is an acceptable ring groove width size. In the piston below, the 1/16" groove measures 1.67mm. Is this ok?
Very sorry for the mix of metric and imperial, but I believe 1/16" is 1.60mm.

Some useful size pistons that I have, also have a 3/32" groove. Would these be readily available? They are +0.060" pistons.

Finally - Several pistons that I have looked at, have had these 'piston ring assisters' (see picture). What is their purpose? Are they piston specific or ring specific?

I may end up just buying new pistons, but I'd much prefer to try to reuse some old ones. I'm not looking to break any speed records - cruising at 40mph is enough for me.

Appreciate any help.

Regards,
Colin

[Robert Leigh]

The piston ring assisters are to increase the radial force of the ring in the cylinder. I don't know whether they are a standard part of that type of ring or whether they could be added to reduce oil consumption by giving a better seal in the cylinder. I have found them on pistons I have removed.