billmerbach

Well I'm so close to putting the engine together but one thing is still nagging me. How can I tell if my piston rings are reuse able I'd hate to have them break in the cylinder upon first crank and then ruin all my work how hard is it to just replace them what all do I need to do to ensure they seat rite. I'd hate to skip this tiny but important part and have the whole engine be a waste

rustyroger

As a rule of thumb, if you have run the engine after fitting the rings, don't re-use them.
The cost of rings vs the cost of rebuilding the engine again makes it a no brainer to me.
A very light hone to brake the glaze on the cylinder walls will be necessary imo.


Roger.

MDchanic

If your engine had signs of worn rings, such as bad compression or using oil, or if you changed any parts directly associated with the rings, such as the pistons or boring the cylinders, you should replace them.

If you didn't do anything to the pistons or the cylinders and the engine had wear, then you need to break the ridge before installing new rings, or the sharp new edge of the top rings could hit the ridge and break them.

- Eric

billmerbach

What do you mean by break the ridge and I think you had said something to me before about reaming the piston? Can you give me some more detail. And roger I thought it was a no brained too but I was told I might be able to get away with reusing them that's why I'm asking

Nilsson

Isn't that the same as reusing a condom?

MDchanic

As the piston goes up and down in the bore, the rings wear against the cylinder walls.
Over time, this removes material from both the rings and cylinders.
Since the rings are in grooves a little bit below the tops of the pistons, they don't go all the way to the tops of the cylinders, and the cylinders don't wear all the way to the top - the wear ends about a quarter inch down into the bore, creating a ridge which you can feel.

The rings start out having a sharp, square edge to them, but as they wear, it becomes slightly rounded, and the edge of the ridge in the cylinder has a slightly rounded corner like the rings.

If you later install new rings with a nice sharp edge, the edge will hit the rounded part of the ridge as the engine runs, causing the rings to break and / or the piston grooves to be damaged.

For this reason, you should ream the ridge if you have one and you are installing new rings without reboring the engine.

Ity should be emphasized that the "right" way to do this is to bore the engine and replace the pistons and rings, and that if the old rings are still working, it's best to reuse them, as they're mated to the cylinders already, but if you have to change the rings and you can't bore the engine, you should break the ridge.



Here's an article about ridge reamers.

- Eric

billmerbach

Ok thanks MD it's the last thing I need to consider before I start assembly I mean if the rings are still flexible I'd assume I can reuse them but then again I have no way to rebore the engine

MDchanic

Usually, if everything is mated together and working well, it's best not to mess with it.

- Eric

billmerbach

Ok cause I've reused small engine piston rings before but I feel its different with a v8

m371961

Have you even measured the bore?

MDchanic

Highly doubtful - I don't think he even has any instruments.

That's why I'm sticking with the "if it ain't broke, don't fix it" line.

- Eric

billmerbach

Yea I have nothing I can use to measure cept a digital caliper

redoldsman

I always cut the ridge before I removed the pistons so the rings did not hit the ridge and break a piston. You can rent a ridge reamer pretty cheap.

One other thing, If you do replace the rings, be damn sure and clean all the carbon buildup in the ring grooves. As the rings wear carbon builds up between the ring and the piston. When you replace the rings with new ones they are going to fit too tight in the cylinder if they go in at all. I learned this many many years ago on a 63 Nova I had.

billmerbach

This is good then when I took out the pistons I had hardly no trouble sliding them out the top

Octania

That's totally acceptable, just turn it inside out.

coppercutlass

That condom bit cracks me up. Just get new rings stock replacment rings run in the 50 dollar range and borrow a hone and give the cylinders a decent finish for the new rings and the correct finish for the stile of rings. I usually finish in 600 but I used moly rings

Professur

you should do that anyhow ... ribbed for her pleasure, like hell.

rustyroger

Replacement rings often had a step in the top ring to avoid hitting the wear ridge back in the day.
An uncle told me that a car he owned never went out of town for about ten years and never got above 40 mph. Until one day he had to make a long trip in a hurry, after a few miles of 70 mph driving he smashed all the top rings on the wear ridge, The car had only travelled about 25k miles, but mostly on choke, the bores were worn like a 90k mile engine (from the '60s btw).


Roger.

nsnarsk65cutlass

If your fingernail catches on the ridge at the top of the cylinder bore, than a ridge reamer is a wise choice,than again taper probably is at the point of an overbore.And no to reusing the old piston rings.Nick

Sampson

I only use one side of my condoms. I have some used ones for sale if anyone would like to get some more use out of them. Free plus the ride.

billmerbach

Hahahaha Sampson lol