View Full Version : Piston Rings 101

06-11-2005, 11:04 AM
I have rectified my oil burning problem on my newly rebuilt (by me) engine. As you can see from this picture, if the oil rings are installed incorrectly, they will do little to keep oil out of the cylinders.


06-11-2005, 11:08 AM
This is a TR-6 engine by the way. Here is a photo of the new piston and ring set, ready to go back in the engine this weekend. With a newly rebuilt rocker assembly, and the head back from the rebuild shop with new valve guides, valves, and springs, I'll be ready to try this again...Should have done this in the 1st place, but live and learn I guess,

1970 TR-6

06-11-2005, 11:47 AM
Mark, were the original oil rings installed incorrectly by a paid mechanic?

06-11-2005, 03:08 PM
My 84 year old father in law was the "paid" mechanic..ha! So now I'm on my own, and with some expert advice from several LBC mechanics, I'm sure the redo will turn out much better....


Mickey Richaud
06-11-2005, 03:42 PM
Mark -

I'm by no means an expert, but one thing I learned early was to stagger the gaps on the rings. If they're lined up, the oil has a natural passage up to the combustion chamber. It's one of those "obvious" things that sometimes get overlooked.


06-11-2005, 04:02 PM
Mark, I'm happy you got it figured out, and sorry you had to pull your motor apart again. Good luck with it this time around.

06-13-2005, 12:13 PM
I'm doing the same thing right now (for the upteenth time) is my 1500-powered racer. The rings/pistons are very much the same design (I'm doing pistons, new crankshaft....the whole nine yards).

I'm not sure what you mean by "incorrectly". If the rings are upsidedown, they might make a slight difference, but I'm not sure it would be all that noticable.

Anyway, for anyone else contemplating a rebuild like this, you may wish to use one of those new rings and check the end-gap. Push the ring into the bore (using a piston) and measure the gap. Should be around 0.008" or so. No more than 0.012" I'd say. Check ring gap at top, middle and bottom of cylinder to see if taper in the bore is excessive.
And don't forget to change the thrust washers....the weakest part of these TR engines.

06-13-2005, 01:28 PM
Are some brand of rings cut with a step on the inside instead of straight cut?

06-13-2005, 02:21 PM
The oil ring expander (only one) actually overlapped, instead of being butted up end to end. This caused the upper and lower oil rings to lay flush against the piston, instead of being pushed out by he expander. I now have Deves rings and I like the design of the oil rings much better. Two seperate expander rings, with the gap set 180 degrees apart. I've checked the ring gap as you suggested with these new rings, the gap is .008-.009 for all cylinders. You should check both compression rings, ie for a TR-6, check all 12 rings. Its easiest if you use one of the pistons to gently push the ring into position to ensure it is set square in the bore. And I did replace the thrust washers, tho mine were not all that bad for the amount of miles on the engine.
As for the compression rings, my set does have a step on the #2 ring, and TOP is stamped on it to ensure the step faces downward. The top ring is identical top and bottom.


06-13-2005, 04:03 PM
The oil ring expander (only one) actually overlapped, instead of being butted up end to end....

Oh, I see. Yeah, that wouldn't be very good!

06-13-2005, 09:45 PM
Are some brand of rings cut with a step on the inside instead of straight cut?

[/ QUOTE ]

There are some rings out there called "gapless rings". It's suppose to prevent some blow-by caused by ring gap. I'm not sure what brand they are or if any are made for LBC's. As far as installing your rings upside down, there is definitely a difference. They are designed to go a certain way to take advantage of compression in the cylinder. Many are chamfered so as pressure builds up, the ring is forced against the cylinder wall. You might not have noticed it know, but you would have sooner or later. $0.02 /ubbthreads/images/graemlins/grin.gif