Just the thought of reusing piston rings makes me nervous! I'll get that out of the way up front. I don't like the idea of reusing piston rings but I wanted to see if I was perhaps wrong; it does happen.

So some of you have likely already read about my engine problems. Basically due to my rocker arms disintegrating internally I had metal shavings in my engine and had to pull it apart. Every last nut and bolt has been removed and the pistons are sitting on the shelf (ok the rods are still attached to the pistons).

The bores look fantastic and still have the cross hatch pattern showing clearly. The engine had 21K miles on it when I tore it down. The question is whether or not to reuse the piston rings or buy a new set for roughly $250 - $300 a set. I'm leaning toward just buying a new set but I'm having a hard time getting my hands on a standard sized set for this engine. Nobody seems to have them in stock without going directly to GM for them; which is a whole different story to tell.

Anyway, what are your thoughts? If it was just a heads and cam swap, nobody would think twice about leaving the existing rings in there. But now that the whole engine is apart, should the rings be replaced for good measure and to save problems down the road?

Thanks for any input!

 

How many miles ? Even then with the motor tore down may as well install new rings .
just my .02 $ Good luck on the build .

 

21,000. Yeah, I'm having a hard time thinking about putting them back in. I'm just having an even harder time getting my hands on a new set of rings.

 

Without knowing the full details of why you are in a position to discuss piston rings requires a few guesses and I will adress the 3 possibilities I can guess at.

Situation 1: You took the motor apart and you are putting the same piston back in the same cylinder without a cylinder hone.....use the same piston rings. No hone will not allow the new rings to seat and thus it will not seal right for power or oil control.

Situation 2: New pistons and no hone....this is a mistake. Disassemble and get it rehoned.

Situation 3: New block, old rotating assembly due to a cracked liner....it has to get a finish hone and you need new rings. Ring end gaps are set by formula/appliaction and they get measured in the bore and file fit. No two cylinders are the same. A new bore needs new rings.

 

Hey Spin,

We had to take the engine apart because we found metal shavings in the valve covers, oil, and oil filter. It ended up being the rocker arm fulcrums coming apart. It's in a different thread.

We're ready to put the engine back together but I can't seem to get my hands on a new set of piston rings. The idea was to deglaze the bores and put in new rings. Then stuff the stock sized pistons back in the stock sized bores. I'm definitely open to better advice though. Can I get the bores honed without changing the bore sizes? I hate to buy new pistons. Or, is the best option to leave the bores alone and just put the stock pistons and old rings back in since the engine only has 21,000 miles on it?

 

Leave the bores alone and put the old pistons/rings back in, they're not hurt and will last for 200K miles easily. The finish on the bores right now is the best you'll ever get and the worst thing you can do is hone it or "break the glaze".

One reason you're having problems finding std size rings is because these are zero clearance engines (the piston to bore clearance is .000"). If you hone the engine, you'll open up the clearance to the point where you'll need new pistons the next size up (.005" oversize) and the accompanying rings. I'd bet you could find .005" oversize piston rings all day long...you just don't see rebuilds using std size rings very often.

The factory uses a plateau hone process and the crosshatch you see is actually perfect for 21K miles. I noticed in your other thread you mentioned the engine wasn't broken in yet because you could still see the crosshatch but that is the incorrect way to look at it. Here's a few links explaining a plateau hone, you'll be able to figure out on your own the best thing is to leave the bores alone and put the old pistons/rings back in:
http://www.enginebuildermag.com/Arti...finishing.aspx
http://www.aa1car.com/library/plateau_finish.htm
http://www.enginebuildermag.com/Arti...er_honing.aspx
Scroll about half way down on the last one to get to the plateau hone stuff. The info on Nikasil coated bores in NASCAR engines and future OEM engines is good stuff as well as the laser structuring.

When the '01 Z06 had the ring flutter problem and GM made the TSB to replace the rings with higher tension rings, the TSB emphatically stated "DO NOT HONE THE CYLINDERS". That's the way they wanted it because the existing finish on the bore was the best they would get, any honing would require new pistons (more expense to GM), and the new moly rings would seat quickly as you read in the links above. The point is that GM has already done what you're proposing many times over with fantastic results. Hope this helps.

Oh yeah, I forgot to comment on this. Your thinking is dead on here and applies directly to your case.

 

This isn't true. As I said above, GM replaced many ring sets on '01 Z06s directing the technician to not hone the cylinders and they never had any problems with the new rings seating. Moly rings on the factory plateau hone are the best for break in, sealing, and long life.

 

Just my opinion, but I would replace the rings and bearings. I would also hone the block just to break the glaze. Have it done on one of the newer automated machines. You can hit it a few times with 320 and then 400 wet stones and not even be able to measure the amount of material removed.

Sometimes a manufacturer will specify a recall process and reuse rings, but it is never a great idea as the cost of the rings is insignificant in comparison to the labor cost of having to remove the engine and tear it down again because one or more of the rings did not reseat.

There is no magic in the factory hone process and a competent shop can actually do better. You can sort through the shops by asking if they use a deck plate to simulate the head distortion on the cylinders. If you want the ultimate hone, find a shop that does a hot hone where the block is brought up to operating temp and then honed with hot recirculating oil (not really necessary at this level).
Also, if you ever wanted to replace any OEM engine parts, now is the time to do it.

 

im with the spinmonster. put everything back in just the way you took it out.

-carl

 

I agree that if the same pistons are going in to reuse the same rings. He said the liners looked great so the mating rings will too. We can differ on the reason but I have less faith than you in GM's tolerances and even less in most dealership's abilities.

I just did a ring replacement on three cracked pistons in a firehawk a few months ago. It had 29k and the rings did seat. I used 3 pistons from a dead LS1. You can get the GM rings from a parts place. Your theory holds in practice.....big surprise that you're right.

 

Thanks for all the posts. I'm going to reuse the rings after I clean everything up and thoroughly inspect everything. I bought everything else new for the engine except rod bolts. I wanted new rod bolts but the GM parts aren't stocked in GM's warehouses so they would have had to come from GM's supplier and I really couldn't justify the cost of the ARP bolts for a stock bottom end in an engine that won't see track or strip time. I hope that was the right decision. This unexpected rebuild is costing me a fortune as it is.

 

I just got done doing a rebuild on my '05. I had the machine shop lightly hone the cylinders and then I put 7 original pistons back in along with 1 new GM piston and new GM rings. The P/N for the rings is 89017484 and I paid like $24 per cylinder for them.

I have put motors back together without replacing the rings and I would have done so in this case but I had no history on the motor so I wasn't taking any chances.

One suggestion I have is whether you replace the rings or not, get some lube called "quick set" made by Total Seal and follow the instructions on the package. The rings will seat in quickly and the motor will thank you for it.