The Stovebolt Site Forums The Shop Area Engine Shop GMC 228 PISTON RINGS

I need new rings for my 228. It has the high dome stock pistons. All the replacement rings I have found are 3/32,1/8,1/8,3/16 which matches up to the ring and dimensions in the GMC manual I have. The top groove on my pistons however measure slightly larger than 1/8 or about 9/64. Has anyone seen this before?

How many miles on engine?

Ed

What is the thickness of the top rings you took off the pistons? It's possible that a previous rebuilder has gotten too energetic with a ring groove cleaner and widened a 1/8" ring groove a little.
Jerry

I have no idea of the mileage. I tore it down and discarded the old rings.

A 228 has a 3 9/16" bore size. You might need to find an appropriate-thickness ring for another engine and adjust the piston grooves to fit the rings. I did that with a Volkswagen engine with an oddball size "big bore kit" installed. In that situation, .040" oversize rings for an 85 HP flathead Ford V8 were the right diameter, but I had to widen the compression ring grooves slightly to accommodate the ring thickness. Piston rings don't know, or care what kind of engine they're in, as long as the bore size and piston groove fit is right. Rings for a 289 Ford and a 350 Chevy are completely interchangeable on a lot of applications.
Jerry

Thanks for the info.

3 9/16" is a 235 bore size, but the 235 compression rings are only .093" wide (I just measured one). Try to find an industrial engine like a Hercules, etc. with a 3 1/2" bore that uses a 5/32" compression ring, get some .060" oversize rings, and make the GMC piston fit the wider ring.
That's assuming your 228 is standard bore, right?

EDIT:

A vendor on Ebay has spacers listed that will allow you to use 235 top rings with those pistons. They are flat steel shims that fit above the piston ring in an enlarged groove to make the top-to-bottom height of the ring groove correct. Drop me a PM and I'll forward the Ebay link, as the PC Patrol doesn't like them included in open forum posts.
Jerry

Actually according to the ID plate it was originally. 005 overbore. It has standard stock pistons in it though?

Few more data points for 1950 GMC 228

My service manual specs says:
Top three rings are 1/8”
Bottom Oil rings are 3/16”

Measured stock pistons and rings on the bench:
Top three rings measure a nominal....... .125”
Oil ring groove measure a nominal.......... .190”

I bored mine .080 over new pistons and perfect circle rings

Nope, the .005" over engines had pistons fitted to the oversize bore, but they used standard size rings. "Standard" rings were supposedly good for bore sizes up to .010" oversize, but in practical terms, anything over .005 was a lost cause. Buick made a few 10 over V8 engines in the 1950's, and neither standard nor file-fitted 20 over rings could keep them from burning oil. The only fix was a bore job, and 20 over pistons and rings.
Jerry

My pistons are zoellner 492 with GMC cast into them so I assumed they were factory std bore pieces as the few oversized ones I've seen were 492-0.

My stock pistons had similar markings to yours.

These are the pistons I used:

https://egge.com/part/egg-1000-l944-6/

They do have the thinner top ring.

Rings:
https://egge.com/part/grt-1200-p2567/

Noted the rings do not fit OEM pistons. Which makes sense since the top rings is thinner.

Didn't some ring manufacturers make "shim stock" in common diameters to cure exactly this problem (only thinner rings are available)?

That's what the Ebay vendor has in his auction- - - -shims that can be used to repair pistons with worn ring lands by widening the groove and shimming above the ring.
Jerry

Somewhere in my piles of "treasures" I have an old WW2 GI ring tool. It has a fixture to hold the piston while the ring groove is cut to the size of the needed ring PLUS the thickness of an oil scraper ring. The ring/scraper combination kept the ring from rocking in the groove. Never used it but probably was adequate at best but in the war years everyone had to "make do". Jerry is right about an engine doesn't know the difference as long as the specs are the same. I had an air cooled diesel Lambordini (not Lamborghini) Italian built air compressor that ran on two cylinders and pumped on two. A piston fractured and replacement was $800 so moved a pristine piston from pump cylinder over to a run cylinder and then used a $20 .040 over 272 Ford piston in the pump cylinder. When people wondered about imbalance due to piston weight difference I said nothing could be more imbalanced than an inline 4 running on two cylinders

Interesting Evan. At one point in my gas company career I was point man on our CNG program. One CNG compressor we looked at for smaller customers was a 460 Ford that could be trailer mounted. 4 cylinders produced power, the other 4 (working in series) compressed natural gas for delivery at 3600 psig. Saw a couple demonstrated and they worked. At a later career stage I saw same setup on small/low production natural gas wells. No telling how many thousand hours those suckers (pushers?) had. Special cams, and high compression pistons were required.

Smith air compressor: 230" Ply-Do flathead L6, 3 ran and 3 pumped.

I've seen lots of jackhammer compressors made from Model A Fords. Cut the frame off at the front seat, weld the front axle with the wheels in the straight ahead position, add a tow bar, and use the cowl-mounted gas tank for fuel. Then the engine was converted with a special cylinder head and camshaft to run on cylinders 1 & 4, and compress on 2 & 3. A big reserve tank was mounted across the front floorboard area.
Jerry

Boys across the highway have a Smith Compressor with a 302 Ford V8. 100cfm and 150psi.