piston ring tight fitting - rebuild

[bob johnson]

Re: piston ring tight fitting - rebuild

so it sounded like you just said the rings for the bottom grooves in the pistons fit fine on two pistons but they all don't fit in the one piston.....correct......the lower ring groove is supposed to be different than the top two... but I thought( from memory) it was the width of the groove.. so it sounds like your one piston is out of round...... so the wide section of this out of round piston makes the ring( that otherwise is fine) spread out so much it wont go into the bore!!.....youre cooked..... you need a new piston....or ANOTHER piston....also could you verify that you mean the pistons are .030" over...or .003" as you previously stated.......bob

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

piston makes the ring( that otherwise is fine) spread out so much it wont go into the bore!!.....youre cooked..... you need a new piston....or ANOTHER piston....also could you verify that you mean the pistons are .030" over...or .003" as you previously stated.......bob

The pistons are 0.030 oversize the other figures are typo's. the rings fit 2 pistons AFTER soaking and scraping the groove overnight... the third is a bit better but still sticking in the lower groove only in one spot ... maybe photos will show...

 

[durban]

Re: piston ring tight fitting - rebuild

as the guys have said take note of the profile of the ring groove & match it up with the rings , in my case the ring gap some how got a little squeezed / closed in one area & dressing it very gently with a file fixed it

 

[glenn property of pam]

Re: piston ring tight fitting - rebuild

old trick use to be to cut a old ring in half then use that as a scrapper to clean out the ring gap

 

[gm280]

Re: piston ring tight fitting - rebuild

The pistons are 0.030 oversize the other figures are typo's. the rings fit 2 pistons AFTER soaking and scraping the groove overnight... the third is a bit better but still sticking in the lower groove only in one spot ... maybe photos will show...

I have one question for you. You stated that after soaking the pistons over night that two of the three pistons have the rings fitting great now. Does the one piston that the lower ring doesn't fit correctly yet have any carbon in the ring groove? Can you visually see carbon in the bottom of the groove? If so, until you can get all that carbon cleaned out it will never work correctly. But I'm sure you actually understand that also. I was just wondering if you could see any remaining carbon in that groove...yet?

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

Got the rings done by micrometer (in mm ) and the new rings are 0.002 thicker than the old ones , BUT as Durbn has posted above , I did find a difference in the lower ring groove in one spot. We ran a feeler gauge around the groove all the way and was having trouble in one spot with the gauge not fitting. That spot was exactly as where i was thinking the ring was getting stuck. It looks like the groove got squeezed or closed together a tiny bit and this is causing my problem.

Durban, after you light filing did you even recieve trouble from that piston or cyclinder ???

 

[durban]

Re: piston ring tight fitting - rebuild

had no problem with mine the motor starts & all the compression readings are within specs

 

[Chinewalker]

Re: piston ring tight fitting - rebuild

It's possible that the motor partially seized while running and the forces involved closed up the ring gap in that area. I've seen some pistons with considerable galling that had the ring gap close up quite a bit. Would make sense that it has to start a little at a time, before the galling got bad enough to see. Your motor might have just come apart before the galling got visible, but the damage had started...

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

had no problem with mine the motor starts & all the compression readings are within specs

thanks for letting me know.

 

[fishfeatures]

Re: piston ring tight fitting - rebuild

It's possible that the motor partially seized while running and the forces involved closed up the ring gap in that area. I've seen some pistons with considerable galling that had the ring gap close up quite a bit. Would make sense that it has to start a little at a time, before the galling got bad enough to see. Your motor might have just come apart before the galling got visible, but the damage had started...

thanks Chinewalker, always good to know what may have caused the issue.