Piston Skirt Recoating

[Mike Graham]

The particular engine that I had trouble with Had Total seal AP rings the first time and Ackerly and childs moly the second time. I have used both brands of rings many times with no issues. Hone on this guy was 820 . The only thing we changed was to have the pistons coated. The engine ran fine but was ready for re ring. Same hone same ring pack. The only thing changed was coated pistons. Engine ran good for about 10 passes then fell off a tenth. Everytime we would leak it leakage would change. Second rings were trashed. Re honed and re ringed.Same results. I have done more than a few stock and ss engines and never had a problem like this before or after. Like I said, the only thing that was changed was coating. I think the coating on this particular set of pistons was too soft and it sloughed off. I did 2 other builds with this coating without problems. I didn't see any gains,but it didn't trash the rings.

[Glenn Briglio]

The coating thickness for some reason can be a problem. I've used Calico to coat piston skirts.They have three different thicknesses of coatings.If I use the extra thick coating I've had problems sometimes with it coming off.

[drgrcr1156]

This rebuild included Total Seal Gapless rings with ultra-low tension oil rings. The fact that when I start it, there is immediate blue smoke coming from the vacuum pump breather tank, leads me to believe the rings have gummed up just as I have read here.

[Jim Hanig]

Originally Posted by Mike Graham

The particular engine that I had trouble with Had Total seal AP rings the first time and Ackerly and childs moly the second time. I have used both brands of rings many times with no issues. Hone on this guy was 820 . The only thing we changed was to have the pistons coated. The engine ran fine but was ready for re ring. Same hone same ring pack. The only thing changed was coated pistons. Engine ran good for about 10 passes then fell off a tenth. Everytime we would leak it leakage would change. Second rings were trashed. Re honed and re ringed.Same results. I have done more than a few stock and ss engines and never had a problem like this before or after. Like I said, the only thing that was changed was coating. I think the coating on this particular set of pistons was too soft and it sloughed off. I did 2 other builds with this coating without problems. I didn't see any gains,but it didn't trash the rings.

Mike i would call Carl at poly dyn used his coating for years never had a problem. 2818946382

[Bob Gullett]

Just was at the dyno Monday with a friends bracket motor. 383 SBC. The guy who did the motor used pistons with Line2Line coatings. All the clearances and assembly and break in was done as per the instructions from Line2Line. Horsepower was down. Changed oil 3 times and oil was black from the coating and the filter had coating material in it. Leakage ranged from 9-55%. Going to tear it down in the next couple days to see the reason but I'm sure the rings are damaged or gummed up from the coating.

[drgrcr1156]

That is sad to hear. I was doing a leak down on one of my cylinders which showed 20%. I disconnected the air line then plugged it back in, heard a little pop and now it was at 2%. This happen again on another cylinder. I drained the break in oil and cut open the filter. I did not see any thing plugging the filter but on one of the runs, the oil pressure dropped to 30 at idle with the break in oil. I poured 2 quarts of 5-20w mineral oil in and let it flush out the pan. I sprayed each cylinder with Marvel Mystery oil in hopes it would loosen up the sticky rings. Had nothing to lose at this point. Installed new filter and Lucas 10-40 semi-synthetic race oil and started the engine, ran to 140 degree water temp. The blow by was significantly reduced. Have not checked the lead down yet since I do not think the engine if fully broken in. Don't have much fuel.

[drgrcr1156]

Originally Posted by Bob Gullett

Just was at the dyno Monday with a friends bracket motor. 383 SBC. The guy who did the motor used pistons with Line2Line coatings. All the clearances and assembly and break in was done as per the instructions from Line2Line. Horsepower was down. Changed oil 3 times and oil was black from the coating and the filter had coating material in it. Leakage ranged from 9-55%. Going to tear it down in the next couple days to see the reason but I'm sure the rings are damaged or gummed up from the coating.

Bob,
Did you tear it down and what did you find?

Bob

[Bob Gullett]

Basically the coating started coming off the pistons. Everything was done including the break in procedure as per the instructions. When the guy who did the motor contacted the piston manufacture they said "bad rings" We'll send you out a new set. It almost looked like the coating was coming off in bits. Not good for any lubrication. Going to bite the bullet and put in a new set of non coated pistons. Suppositley they ask for the cylinder size and coat the pistons to match the bore. Then you take scotchbrite and lightly sand the piston to just fit into the cylinders. The coating then wears slightly to have proper piston clearance. I think the coating itself is a good idea but with proper clearance and a minimum amount of coating on the piston. It almost looks like it was put on real thick.

[MR DERBY CITY]

SWAIN Coatings....

[astikhossw]

Hey Bob when you put a caliper on the skirt did it come within spec per piston to bore and piston skirt diameter after the break in,and did you run it up to full rpm on the break in.