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304065's Avatar
 
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Leakdown Results 1966 911 Normal

are NOT good. . .

I 40%
II 12%
III 45%
IV 7%
V 45%
VI 45%

The leakage is past the rings, I can hear it coming from the breather when you crank up the air pressure.

I went through the stack of receipts looking for a piston set. . . there isn't one! Just a set of rings, and a hone to the cylinders. Which is OK, if the pistons were within spec 20 years ago, but the above results suggest that it's gotten worse.

What I really find incredible is the amazing consistency between the low cylinders, all around 45%.

I'll repeat the test in a thousand miles and post the results here.
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'66 911 #304065 Irischgruen
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 04-03-2005, 05:48 AM
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'66 911 #304065 Irischgruen
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 04-03-2005, 06:01 AM
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I had one of those leakdown testers and I did not like the results. (it should say Star products somewhere on it)

That tester seemed to be at least 10% - 15% off of my older one.

My older one is a matco - you TDC the cylinder, and pump air in - it has two gauges - if you put 70 PSI in you look for 70 PSI out.

The tester you have pictured, unless I'm mistaken is the type where you set the dial to the 0 point and then connect the air hose to the cylinder.

After testing the old style and the new style side by side on the same motor, I do not and will not trust results by the cylinder leakage tester you have pictured.

10 - 15% may be fine for a chevy, but on a Porsche, you really don't want anything worse than 4 - 5% leakage.

I have a new leakdown tester (from Germany) on order. when it arrives, I will post the results

AFJuvat
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Old 04-03-2005, 08:13 AM
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Was the engine stone cold when you took the readings?
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Old 04-03-2005, 08:41 AM
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No, not stone cold. It had been run to operating temp (not that I know what that actually IS, see my thread on malfunctioning oil temp sender), it sat for about half an hour, and then the test was performed.

It certainly could have been too cold. . . when it warms up outside I'll give the engine a good thrashing and repeat the test immediately thereafter.

AF, I have no reason to doubt the gauge or procedure at this point, it works fine on my 911E, which shows about a 4% leakdown in all jugs.
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'66 911 #304065 Irischgruen
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 04-04-2005, 05:54 AM
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AF - what tester is that - can you give a website, or product name/no ?
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Old 04-06-2005, 09:07 AM
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Epilogue:

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'66 911 #304065 Irischgruen
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 04-14-2008, 01:28 PM
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John,

What caused the piston-to-valve contact?

Wrong parts?
Incorrect timing?
Other?

Is that a broken top ring?
This is where checking all the specifications is so important.
Others might include incorrect valve clearance (ie, less than none) setting.
A broken cam.
A jamed broken rocker arm.
And more.

The key is to investigate the symptoms and explore all the possibilities.

More tomorrow.

Best,
Grady
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Old 04-14-2008, 03:20 PM
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Grady, this is an old thread but I never added the pic of the broken ring. When I tore it down there were FIVE, repeat FIVE, broken compression rings-- caused by new rings being installed in the original 1966, oil-ring-below-the-pin pistons. No doubt the original ring grooves were worn beyond spec resulting in the breakage within a few miles of the original rebuild 22 years ago. Rockers (forged) have been replaced with cast-iron, reconditioned with new adjusters by Ollies, cams are new DR, heads re-done by Anchor Atlantic. In short, everything has been redone. . . I just posted the broken ring pic to show that, in fact, a leakdown test DOES provide you with useful diagnostic information!

Take care, hope you are well.
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'66 911 #304065 Irischgruen
Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13)
Ex-'88 Carrera (Sold 3/29/02)
Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04)
Old 04-14-2008, 04:06 PM
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