Piston/Ring issue???
 

I purchased a new set of pistons from a well known manufacturer and also purchased a new set of rings(Conventional) from a well known manufacturer.

Pistons are 1.5mm, 1.5mm and 3mm. Rings are .028 with .030 gas ported spacers for the compression and .028 Napier with .030 spacers for 2d position. Piston ring grooves are .0593 top and .0595 2d position. Correct radial depth groove for rings.

When I was ready to install I pressed the rings into the groove and rotated them. All the top rings were fine, but several of the rings in the 2d position would not rotate and would "Stick" in the groove.

Top rings with gas ported spacers no problem. Had several rings in the 2d position that were sticking. Lapped the spacers for a little more clearance but rings were still sticking. Even tried swapping non sticking ring/spacer, same problem.

Any feedback would be appreciated.

I will not identify the Companies involved at this time, as they are trying to figure out what the problem is.

This is not a Witch Hunt, just would like some feedback. PM would be best.

Has anybody had these problems lately?? At this time the pistons and rings have been sent back to their perspective manufactures to check for any problems.

Thanks in advance.

RJ

Re: Piston/Ring issue???
 

It would seem that after swapping non-sticking rings/spacers into grooves that still were sticking, the only thing left is ring grooves machined improperly. I'm figuring you already miked the rings and checked for flatness.

Re: Piston/Ring issue???
 

I mic'd the rings and spacers and they checked, but had no way to really check the ring groove width or flatness. I ran a .059 pin around the groove and felt no tight spots, but I am thinking the grooves might not be perfectly flat.

Thanks
RJ

Re: Piston/Ring issue???
 

Just for my education, can I ask what your particular combo cost's ?

Re: Piston/Ring issue???
 

Way too much!!

RJ

Re: Piston/Ring issue???
 

RJ,
I sure am glad you called today to discuss this problem. I still think they have a wave to the groves. I was just about to pull the trigger on a set of pistons for a Drag Pack customer. Since there are only 2 different companies that are approved I think I will choose the other. Not because of the problem, but because it wasn't taken care of. At this point I'm very glad I have procrastinated on ordering parts for this build. Like I said when we closed our call... Thanks, I think?? ;~)

Re: Piston/Ring issue???
 

Adger

Like I told you today, The piston people told me they found nothing..... the ring people said they would call me back today and I never heard from them. Sort of makes me nervous.

At this point I feel like the "Rat caught in the trap, really don't care about the cheese anymore,.....just want out of the trap!!

So I don't care who or what is wrong, I just want it be fixed so I can put this thing together.

Later Bud

RJ

Re: Piston/Ring issue???
 

It's possible there is a small radius at the bottom corner of the ring groove. If the rings have a sharp square edge, when the seat in the bottom of the groove this could cause this rotation problem. This could be as small as .001-.002 radius and not visible to the eye. Is there a chamfer on the inside edge of the rings and spacers?
Interesting, keep us posted.
George

Re: Piston/Ring issue???
 

RJ Could you make a straight edge the same thickness of ring groove or a ,001 less and walk it around groove to find a sticking spot. I did this on a nitrous piston that had a problem of stuck ring. Couldn't see it by eye but found it with straight edge in groove when rotating it around piston. Ring groove was wavy as suggested by someone else

Re: Piston/Ring issue???
 

Jeff
I used a .059 checking pin and felt nothing, but that's a few tenths less than the actual groove thickness according to my piston spec sheet.

Still waiting to hear back from Piston company.

In the future I will check for fit of the rings/spacer in the piston grooves when I receive them.

Taking something for granted is asking for problems, no matter what the situation.

RJ