02-25-2018, 11:53 AM
Additional information...
Neither engine over heated, plugs were wet and dark brown and no evidence of sticking on the pistons or cylinder walls.
I always am conservative making ring gaps a minimum of 0.080" and make sure to square the ends of the rings and also deburr them.
I went thru this a few years ago and am super careful how I set up the rings and pistons.
The 91B had run at least 3 seasons before failure.
I think these were not caused by anything except poor fit of pin into piston which I have no way of checking.
On pistons where I pinned the rings myself, I have never had a failure (So far)
On using Wiseco pistons, I have had several ring pins fail but on Steve O's recommendation I now grind the outer surface of the pin a bit so it does not contact the bore and that has helped. I may start doing that on all pistons now.
I was able to save the block on the Mc91 engine with a 0.010" overbore.
The 91 head cleaned up nicely removing around 0.020" off the head which reduced the size of the combustion chamber around 1cc which will up the compression a bit so I installed a 0.005" thicker head gasket to compensate because it is a gas engine.
I have not tried to mill the 101 head and have not done anything with the block as yet but there are two scores and both are deeper than the 91 had. It was already real big so I may not move to try and save that.
Neither engine over heated, plugs were wet and dark brown and no evidence of sticking on the pistons or cylinder walls.
I always am conservative making ring gaps a minimum of 0.080" and make sure to square the ends of the rings and also deburr them.
I went thru this a few years ago and am super careful how I set up the rings and pistons.
The 91B had run at least 3 seasons before failure.
I think these were not caused by anything except poor fit of pin into piston which I have no way of checking.
On pistons where I pinned the rings myself, I have never had a failure (So far)
On using Wiseco pistons, I have had several ring pins fail but on Steve O's recommendation I now grind the outer surface of the pin a bit so it does not contact the bore and that has helped. I may start doing that on all pistons now.
I was able to save the block on the Mc91 engine with a 0.010" overbore.
The 91 head cleaned up nicely removing around 0.020" off the head which reduced the size of the combustion chamber around 1cc which will up the compression a bit so I installed a 0.005" thicker head gasket to compensate because it is a gas engine.
I have not tried to mill the 101 head and have not done anything with the block as yet but there are two scores and both are deeper than the 91 had. It was already real big so I may not move to try and save that.