Thu Apr 12, 2012 6:36 am
Repro piston groove problem
I found a problem on a new piston. I do not know the brand but it has a sign cast in, on the inside. It is a circle with a horizontal line inside and a somewhat larger circle around it not, centred but tangentially touching, making what looks like a partial solar eclipse or a 3/4 dark moon. Anyone who knows this brand?
The oil control ring has an expander. When I tried to push this ring in the groove, it required tremendous force. Definitely not good. It looked like the groove was possibly not deep enough. I then compared things with a 40 year old Bohnalite piston, put on NOS HD rings and found that things looked fine. Measured the groove depth and found that it was 1 mm (.04") deeper in the old piston which explained everything. (Rings and expander were the same design on both pistons.) Has anyone seen this type of problem before?
The oil control ring has an expander. When I tried to push this ring in the groove, it required tremendous force. Definitely not good. It looked like the groove was possibly not deep enough. I then compared things with a 40 year old Bohnalite piston, put on NOS HD rings and found that things looked fine. Measured the groove depth and found that it was 1 mm (.04") deeper in the old piston which explained everything. (Rings and expander were the same design on both pistons.) Has anyone seen this type of problem before?