On my new pistons the middle ring doesn't rotate around the piston when it's installed. It seems like it's getting hung up in the same spot on each piston. Is this normal? If not where could my problem lay? Assume they are the correct rings. Are the compression rings different thicknesses?

 

Paul,

Are your ring lands pinned?

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Later,
Vader
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What does that mean? Ring lands pinned??

 

Paul,

Some aftermarket pistons used to have locating pins or machined steps for retaining the ring ends (compression only) in a given position. I haven't seen nor heard of these for a long time in automotive engines, but I thought I'd just throw it out there in case you have a set of custom pistons.

If the grooves are clean the rings should be able to fit in any position without binding or interference. If you have an old ring, you can break a section to use as a cleaner/feeler. Run it around the circumference of the piston ring grooves to detect any interference. If you discover a tight spot, inspect it closely for nicks, burrs, or even possibly a locating pin. (I know, I'm showing my age...)

If you are using old pistons, it's possible the ring lands are not adequately clean, and the broken ring segments can help with that, too.

Try to pre-fit the piston in to a bore by compressing the ring and starting it upside down from the top (con rod sticking out the top of the bore). Once it's into the bore squarely, try rotating the piston 360° to check for interference. The ring will try to stay stationary in the bore, and you should detect any high spots or sticking easily. Note the relative location of the piston rotation, remove the piston/ring, and start inspecting the grooves near the ends.

Good luck.

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Later,
Vader
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Vader,
I am using brand new Speed Pro pistons. They are all having problems with the second compression ring and I have no idea why. Everything that can possible hold me up on this engine is happening!! Should I take the pistons to the machine shop and have my machinist take a look at them to make sure they aren't defective or something??

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Riccioli Performance Motorworks

--RPM Racing--

-Currently building first ever engine. 383 with Super Ram plenum and runners, Edelbrock lower intake, Bosch 24# injectors, either AFR or Trick Flow heads, MSD ignition.
-Will be installing Baer Brakes
-Will be installing full Spohn suspension in rear
-Art Carr 700R4 trans??

 

yuor manual will, or should give you a clearance between the ring and the groove. won't be very much, but you can check it with a feeler gauge. i'd do like mr. vader said and break a old ring and use it to check for a burr or anything that could cause you problems.

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-=ICON MOTORSPORTS=-

 

Paul,

It may sound like a silly question, but since I'm not there to see for myself, are you sure the rings are installed correctly? It's possible they were packaged incorrectly on the cards, or are not the correct application. Either the positions are reversed or the cards contain the wrong ring sets. It happens.

The fact that the second compression ring on all the pistons is causing problems should be an indication. There are several designs of rings and your ring lands may not be appropriate for the type you have. Some have bevels or steps on the inside diameter of the rings.



It's also possible the rings were packaged with the first and second rings reversed, so the second ring should be in the first groove, and vice-versa. Since the typical side (top?) clearance of the rings is around 4 tenths (0.0004") it is possible to have them a little too tight without having a significant, measurable difference. You could check with a feeler as Ed suggests, but the thinnest feelers I have are 0.001", although I have used 0.0005". The rings could be removed and trial fit backwards. Try to fit the ring in the lands by rolling the outer edge of the ring around the circumference of the piston. The ring should bottom in the groove all the way around.

It's also possible that the pistons have a manufacturing defect that is preventing the rings from seating. The grooves could have a slight taper. Again, trial fitting with a broken ring ar a new ring rolled around the outside could determine this.

Again, good luck.


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Later,
Vader
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I figured out my problem!! Then I spent 3 hrs fixing it!!! My 383 has had all kinds of clearance problems and the pistons were in the machine shop twice to have the skirts cut. I think what happened is that when the pistons were secured in a vise or whatever they use it slightly distorted the pistons. I used a small file and filed a very minute amount off of each piston where the ring was getting pinched. It's all good now. Now I just pray I don't have any clearance problems with the cam and the rod bolts!! Thanks for the help guys.


------------------
Riccioli Performance Motorworks

--RPM Racing--

-Currently building first ever engine. 383 with Super Ram plenum and runners, Edelbrock lower intake, Bosch 24# injectors, either AFR or Trick Flow heads, MSD ignition.
-Will be installing Baer Brakes
-Will be installing full Spohn suspension in rear
-Art Carr 700R4 trans??