The Stovebolt Site Forums The Shop Area Engine Shop "Koppers" piston rings

Hey everybody, I'm kind of starting over in a different direction from my last thread on 216's/early 235's.

I got my "new" set of Koppers American Hammered piston rings from a guy on e-bay. The price was right so I couldn't pass them up. My question now is whether or not I can actually use my good deal or not. This set of rings are a different style of ring than the originals, but, they are the right size. The top comp. ring is simple enough, only diff. is that it has a shoulder on the top inside. The second comp. ring is labeled "FLEX POWER" and has a groove milled in the face, and has 3 "pressure ducts" (so called by mfg.) on the lower half of the face. The oil ring is a cast ring with slots milled in it, as opposed the more familiar style zig-zag (VVVVVVV) oil ring. The oil ring also has a beveled face.

All rings are the right sizes (#1 & #2 are 3 9/16 x 1/8) and the oil ring is 3 9/16 x 3/16. The 2nd and 3rd ring also have and expander band behind them. I set up one piston and put my ring compressor on it, and it seemed pretty hard to compress. I haven't put any pistons in the block yet. I didn't know if they're that tight because they're new or what. This is my first Stovebolt motor, I'm used to V-8's so a lot of the little tips and quirks of a 'bolt are new to me.

BTW this is a standard set of rings, so I'm not trying to compress a .030 ring in a std. piston, I checked end gap in the bore before I started.

I think the expander behind the ring is optional, depending on the depth of the ring groove. Measure the thickness of the ring, plus the expander, and be sure there's enough depth to contain the assembly, without stacking solid and binding the ring against the cylinder wall. When were these rings manufactured? It might be wiser to take advantage of more recent technology, rather than use "new old stock" stuff from years ago. I haven't seen single-piece oil rings used anywhere in at least 30 years. You might have a good museum exhibit, rather than a good ring design.
Jerry

Oh they're old alright. The rings I pulled out had an expander behind the 2nd comp. ring also. Any disadvantage to a one piece oil ring? When this truck is finished it won't see many miles. Mostly just two days in August when we have our local Threshing Bee. Maybe a dumb ques. but what about using the original oil rings and replacing the comp. rings after a nice hone. Motor has original 65,000 miles.

NONONONONONONO! Replace rings in full sets! Once a ring has been removed from contact with the cylinder wall, it has to re-establish a running fit if it's reinstalled,and basically go through the break-in procedure again. The newer design oil ring with an expander and two thin rails is able to conform to cylinder irregularities better than the old one-piece ring. It also resists clogging of the drain holes better. I'd suggest going to a modern-design 3-piece oil ring, and whatever compression and scraper rings the set contains. There's no point in taking a leap backward in technology just because new "old" parts are available. That's particularly true of one that doesn't get driven regularly. The newer-designed rings are more likely to last longer in occasional use.
Jerry

Hi Keith,

As discussed in your earlier thread, the problem with using newer type oil rings in these older (pre-'54) 235 engines is that the sets are harder (but not impossible) to find. It seems most new complete replacement ring sets for the 235 are for the '54-up engines, which use different size compression rings.

If you don't want to/can't spend the $ on a full new set, I don't see why you can't/shouldn't use the NOS set with the one piece oil rings. They'd probably last quite a while if the truck is driven as little as you say. All of the 216/235/261 engine family originally used the one piece oil ring (I think), though improvements were made over the years. For example, in '54, a new spiral spring type of expander was incorporated into the back of the oil ring.

If you decide to go modern, I had mentioned in the earlier thread that Hastings Manufacturing (hastingsmfg.com) makes ring sets for the pre-'50 235, with what they call a "Flex Vent" oil ring (a "revolutionary" ring that they introduced to the World in '56). They have a warehouse in your neck of the woods, in Minneapolis. I also found a set listed by Deves Piston Rings (deves.com), with modern-type oil rings.

Thanks Curt, I honed and cleaned the block and began reassembly w/my "NEW" rings. Have only reinstalled 2 pistons so far and everything seems to be moving as it should, tightly but not too tightly. Original babbit rods plastigaged at .0015". I think those NOS rings should function just fine, was mostly just curious about the one piece oil ring, never seen them before. As far as the 2nd ring expander band, left it out. I think it was just too much material compressed into the groove, and the new ring is a couple thousandths thicker that the old one. I guess we'll just have to wait and see how it all pans out.

I hope nothing ends up in the pan!

Good Luck!

No pun intended, but I hear ya! :rolleyes: