FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: msundstrom on October 23, 2017, 03:16:09 PM
-
What is causing the etching at the top of the cylinder and the small scratches? Are they related? This is a 505 BBC on 45% Nitro. After 3 passes cylinder leakage was 8%, after 17 passes it ranged from 14% to 28% with no oil on the plugs but down on power. All eight cylinders/pistons and rings look the same and the top ring is very worn but the second looks great. The ring ends have not been butting and there is no signs of detonation on the piston, spark plugs nor the top rod bearings.
Thanks
Mark S
-
It looks like too much fuel to me ! You can do just as much damage to a motor from being too rich ! This is a piston from my sons car with too rich on a ntrous tune up
-
Is it washing the oil off the piston and walls?
-
It sure looks like it to me ! I should also add that we were also having a problem with a piston that was not properly built for what we were doing !I would highly recommend that you box your worst piston up and send it to Bill Miller . We did this with a Ross piston and Bill Miller himself called my son and explained that the Ross piston was not a bad piston but is just not right for his combination ! Miller built him a new set of pistons and some suggestions and they work great ! My son is now going mid 6.50's at 209 with a 572 big block with 2 nitrous kits and no piston issues !
-
msundstrom:
Injected nitro?
How much compression ratio?
-
Yes, injected nitro and 12.23:1 compression
-
Could the ring issues be from the piston cocking in the bore like it does?
-
My thoughts too. Above the top ring land is usually several thousandths smaller in diameter than the skirt and for it to be contacting the wall so heavily I wonder if you have too much bore clearance, exacerbated by an unfavorable L/R ratio?