yubh8tn
(Junior Member)
10/25/20 05:11 PM
piston ring gap is massive?

Hey, so I'm in the process of rebuilding my engine and I ordered these piston rings. They say they're for our car, but after putting them in my cylinders, I realized the gaps are absolutely massive.

New ring on the right, old ring on the left. As you can see, the ring on the right has a giant gap. The gap on the left is about 0.015, for reference. Why is it so large? Am I doing something wrong?


This is what the website says for the rings I ordered. I didn't see this page until after ordering them. If .50mm is .020", then that means 1.50mm for the second group is .060"???? Why is it so massive?


Here's the box, if it helps.


fuel
("Just to be pedantic!")
10/25/20 05:23 PM
Re: piston ring gap is massive?

Those group measurements are referring to the thickness of the rings. First group is top ring at 1.2mm, second group is second ring at 1.5mm, and then oil control rings are 3.0mm in diameter. However I believe these rings are for the 7 bolt engines, as I am sure the 6 bolt E39A Galant VR-4 rings are 1.5mm, 1.5mm, 4mm respectively.

yubh8tn
(Junior Member)
10/26/20 02:12 AM
Re: piston ring gap is massive?

Okay, I appreciate the response and explanation. That explains why the group numbers are so wack, but why is the gap so large? I'll contact the seller

iceman69510
(Turn Right Racing)
10/26/20 09:34 AM
Re: piston ring gap is massive?

Maybe mis-boxed 85.5 or 86 mm rings. No bore job done?

yubh8tn
(Junior Member)
10/26/20 03:48 PM
Re: piston ring gap is massive?

yeah not bored, just honed. The seller offered me a refund so all is good

BLUELIGHTSBABY
(Junior Member)
11/01/20 12:52 PM
Re: piston ring gap is massive?

Depending on boost levels you plan to run, The higher the boost, the wider the gap. you want about a .20 to .24 gap on top ring. Gap the second ring the same as the top. This is per manley ring install. (their rings are made by total seal) however, they are not true "total seal rings".

iceman69510
(Turn Right Racing)
11/02/20 11:47 AM
Re: piston ring gap is massive?

Some more feedback on this (from another board member experienced with machining who mentioned it to me):

Machine work looks a little questionable, both on the right bore and the deck. Deck looks inconsistent on the surface finish.

The bore should probably be checked, because judging by the lack of crosshatching and a very rough surface finish, the excessive ring gap may be caused by the wrong grit honing stone, run too slow with the incorrect lubricant, and now the bore is oversize for stock rings. A rough finish would eat that ring set in less than five minutes, and probably collapse/break a ring land when they seize up and weld themselves to the bore from the friction.

That block may need to be re-machined at a better shop.


yubh8tn
(Junior Member)
11/02/20 05:06 PM
Re: piston ring gap is massive?

...shit. That's the worst news I've gotten in a while. I'm confused though, as the original rings still have correct gaps. If I switched around the rings in that picture, then the ring on the left would have the bigger gap and the right bore gap would be correct. It's the new rings that are the problem. Also, I'm new to machinework so I'm probably wrong, but isn't that finish in the bore the crosshatching? I'll take a picture with a better angle.

iceman69510
(Turn Right Racing)
11/03/20 07:57 AM
Re: piston ring gap is massive?

Perhaps the photos are not clear. And your additional feedback does sound like the rings had an issue. Do you have bore measurements?

yubh8tn
(Junior Member)
11/17/20 06:36 PM
Re: piston ring gap is massive?

Ok. Sorry for not posting any pictures, my phone camera is busted and I can only post pics when my friend is over.

Anyway, I ordered hastings rings for my car from Summit Racing and they had the exact same problem. Gap was massive. This means I am obviously ordering the wrong thing. The question is, though, what is the correct thing to order? The rings that came off of my pistons are correctly gapped. How do I figure out what I need to order? Obviously these "stock" rings wont work for some reason.

Using a ruler, the bore comes out to exactly 85mm, but a ruler isn't exactly an accurate tool. I'll call the shop and ask what the bore was. (they told me standard when I picked up the block)



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