Piston Ring gap Problem

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May 28, 2002 | 05:36 PM

Eran Sharon

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From: Israel

Piston Ring gap Problem

Hi all,

I recently purchased a piston ring set from "GOETZE by federal mogul" and found the top compression ring gap was outside the maximum allowed - 0.63 mm (0.0244") instead of 0.40 mm (0.0157"). The Bottom compression ring gap was O.K @ 0.30 mm (0.0118").

Failing to believe this is happening, I repeated the measurement on all cylinders/rings - The block has between 1-2 thousands of a mm wear on all cylinders.

The Dealer who had sold me these has also measured this gap in their shop on other blocks using other sets from GOETZE, 11K miles away from me...

In my despair I am considering the purchase of a Deves set. The Factory originals are a bit expensive for me as a second set (Engine is Stock)

Any Opinions ? Am I right to refuse closing my engine with these parts ?. Any experience with Deves/Federal Mogul?

Thanks,
Eran

Thought anyone could shed some light on the matter <img src="confused.gif" border="0">

May 30, 2002 | 02:53 PM

WallyP

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From: Ball Ground, GA

>I recently purchased a piston ring set from >"GOETZE by federal mogul" and found the top >compression ring gap was outside the maximum >allowed - 0.63 mm (0.0244")instead of 0.40 mm >(0.0157"). The Bottom compression ring gap was >O.K @ 0.30 mm (0.0118").

One possible answer for this - Original rings are usually chrome and/or moly, and the Porsche specs would be for this type. Some vendors furnish replacement top rings in plain cast iron. They don't last as long, but they break in more quickly, seal well, and are more forgiving of worn cylinder bores. These cast iron rings also expand a bit more than chrome/moly rings, and thus have larger end gaps. The gap that you have (0.024") is within acceptable limits for new iron rings.

May 30, 2002 | 06:26 PM

Eran Sharon

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Track Day

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From: Israel

Thanks, Wally
I had a notion that this is possible, but was way too afraid to close the engine without expert advice.

Guess I will start closing the engine with my cast iron rings (sound much duller than "chrome/moly rings"...). I will be happy to share my experience with this wonderful forum during run-in.

Thanks to this forum I am now not "alone". There are only 3 (repeat: three) sharks in my country. needless to say, specialist knowledge and parts are seldom encountered here <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

Eran Sharon

1982 Euro 928S/5 speed

Feb 4, 2003 | 09:06 AM

Eran Sharon

Thread Starter

Track Day

Joined: May 2002

Posts: 16

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From: Israel

Hi
Although it has been some time since the last post on this thread, I thought I'd comment on WallyP's help on this subject:

After driving some 3000 miles, I must admit - you were SPOT ON the matter !. Apparently the ring gaps appear fine and the engine runs smoother than I can ever remember. It even smells "fresh" and clean. Even if the rings last 100000 miles I am content !

Thanks again, Wally, and all members of this forum, their help proved invaluable time and time again. I am so glad for having such a group !

Eran Sharon
----------------
82 928S-Euro 5speed
A shark in Israel...

Feb 4, 2003 | 10:42 AM

Greg86andahalf

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From: Maryland

Eran,

Cpngrats on the success. Sounds like a good time to join Rennlist as a dues-paying member.

Greg

Feb 6, 2003 | 01:33 PM

Fastest928

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Joined: Mar 2002

Posts: 1,617

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From: California

Eran,
To test the ring gap and its effect on cylinder sealing, perform a leakdown test. This will tell you if you have good sealing.

Generally, think of a ring gap as a scrape in the cylinder wall...

Cheers,
Marc
DEVEK