Special tool for compression check?

[911-m5]

Is there a special tool for this? I have a gauge with the flex line on it, but I see no way to get it tight in the whole without removing the upper valve covers. Is that what I have to do or is there a gauge thats made to fit in there that you can tighten outside of the covers?


Thanks

Allan

[Bill Verburg]

You need a screw in guage like this

[Formerly Steve Wilkinson]

What you need is the kind of dual-gauge compression/leakdown tester that is routinely used for compression checks on lightplane engines. It is entirely unlike an ordinary car-engine "compression tester," which has a rubber nipple that you squash into the spark-plug hole while somebody briefly cranks the engine. What you do to get a real compression tester tight in the, uh, "whole" is that you thread it in like a spark plug.

Then you need to know what you're doing and how to do it, though the instructions that come with a good leakdown/compression tester could be enough to explain the process.

10 years ago, when I bought my most recent one, they were about $70. Dunno what they are now, but they are NOT one of those Pep Boys things with a single gauge on the end of a rubber hose.

Go to Aircraft Spruce or Wicks to find one.

Stephan

[Bill Verburg]

Hint, a leak down test is an entirely different animal

not all compression testers are squeeze on, do avoid those.

[Formerly Steve Wilkinson]

If you're going to do a "compression test," which is of minimal use anyway, with one of those screw-in devices, why not do a compression-leakdown test? Same amount of effort, considerably more information.

Stephan

[911-m5]

oops on the "whole". lol I was in a hurry.

Thanks

[aj88cab]

How about this.

http://www.kalequip.com/product_detail.php?pid=60

I just got one, but haven't had the time to try it yet. It looks like it might be a bit long to get the quick-connect attached, so maybe a little shortening or adapter will be required. Maybe this weekend I'll give it a try.

[walt]

Nice looking tool, but I wonder if you could install it given the confined space.

[aj88cab]

Originally posted by walt
Nice looking tool, but I wonder if you could install it given the confined space.

I'll let you know this weekend

[911-m5]

AJ,
That's kind of what I had in mind when I started this thread!
Let us know how it works.

[Formerly Steve Wilkinson]

Okay, I continue to be baffled by why you would want to go to all of the effort to buy and attach to the plug port a stupid compression tester when for the identical effort and moderately more expense you could do a compression/leakdown test, which shows you infinitely more about what's happening to the rings and valve guides (none of which a "compression test" will specifically show you). Is it because you don't know what a leakdown test is?

Stephan

[aj88cab]

Actually, I will be doing a comp/leakdown test. The extension seemed like a nice tool to help the process.
Andrew

[H20911]

this

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4558534087&category=43989&sspagename=WDVW




Instructions From the site :

Engine Leak-Down Tester

Operating Instructions:

Warm the motor up to normal operating temperature.

Remove all spark plugs. Put transmission in neutral. Block wheels.

Remove the rocker arms of the cylinder to be checked.
Important note: TURN THE CRANKSHAFT SO THAT THE PISTON IS AT BOTTOM DEAD CENTER. If you do not, the motor will suddenly turn over when you connect the air, possibly causing serious injury to you or someone else working on the motor.


Screw the hose into the spark plug hole of the cylinder to be tested. Be sure that it is tight enough to completely seal. Leakage here will give you a false reading - lower than true leakdown.

Connect the hose to the tester and to your air supply. Ideally it should be between 110 and 125 psi (175 psi MAX) and be clean and moisture free.

Adjust the regulator until the left gauge reads 100 psi. (See Note A below if you air supply cannot maintain 100 psi on the left gauge.)

At this point the right gauge will display the leakdown as a %. For example 92 psi on the right = 92% leakdown or 8% leakage (100 - 92 = 8). See the chart below for leakage %. If you get an extremely low leakdown % and the motor seems to be running well check for a blockage in the precision restriction between the gauges.

It is best to lower the regulator setting before disconnecting either air line to avoid rapid pressure changes to the gauges.
NOTE A: If your air supply cannot maintain 100 psi on the left gauge you may use a lower pressure.

Talk to your engine builder about what leakdown % should be expected on new and used motors. Most leakage is past the rings which, when worn, can't seal the compression properly and costs you power. Once you have established a maximum leakage before rebuild, test your motor often to keep it running its best.
Don't drop this unit or your readings could be affected. Store it in a clean dry place

[911pcars]

Use the Sears/Penske compression gauge with a quick-disconnect flex hose connector. It's much easier to thread in the hose w/o a gauge on the end.

I don't think that long, rigid extension tool will make it given the available space around the spark plug opening. If it works, let us know.

Sherwood

[JasonAndreas]

Originally posted by Formerly Steve Wilkinson
you could do a compression/leakdown test, which shows you infinitely more about what's happening to the rings and valve guides (none of which a "compression test" will specifically show you). Is it because you don't know what a leakdown test is?

What does a leakdown test tell you about valve guides?

[911-m5]

Steve,

I know what it is. Did it ever occur to yo that I don't have a compressor?
A comp test will tell me more than nothing. As a matter of fact I did one on a friends old Land rover recently - it turned out he had 2 exhaust vavles with holes in them. furthermore, i don't think there is any reason to start being a jerk about it.

Allan

[Formerly Steve Wilkinson]

No, it never occurred to me that you didn't have a compressor. I never intended to "start being a jerk about it," but if you don't have even a little tiny compressor, there's no sense in even talking about doing any kind of serious maintenance.

I don't have a garage. I don't have a carport. I don't have a shop. I have a driveway, tools...and a compressor. You should get one.

Stephan

[304065]

You fellas might consider cutting Stephan a little slack. He's built up enough goodwill in this community over the years.

Compression tests alone themselves are fine, but the nonspecific nature of the test is a limitation. Anyway, for how long could one experience worn valve guides without something showing up in the seat? Too much slop is going to result in the valve overheating and burning soon enough.

Now, to respond directly to the original question, even the leakdown tester you buy isn't perfect for doing a 911. My reason for saying that is that it needs to be done HOT, and the aircooled engine does, by design, a pretty good job of radiating that heat, so there's little time to insert it slowly and grope around looking for the hole. Anyway, I found a short, like 4" length of aluminum tubing that had the same ID as the OD of the 14mm leakdown tester, and slipped it over the insert with a nice tight fit. By sliding it in and twisting the hose with my other hand, I can fit it into the spark plug hole and get it threaded rapidly enough to result in meaningful test results.

Grady Clay actually machined a quick-disconnect adapter for this, you might search under his name and leakdown for a nice picture of the best setup.

Good luck!

[911-m5]

Thanks John. Sorry, if I seem a little short, but I realize the merits of both tests and I just wanted an answer to my original question. I didn't need a lecture or somebody asking me if I knew what i was talking about.
steve, I apologize for being rude, but the tone of your response was not that nice either.

Allan

[Formerly Steve Wilkinson]

Point taken, and I'm sorry. I in fact meant, "It's entirely possible that you actually aren't aware of what a leakdown test is, which means we need to refine our communication." Not "Are you so dumb you don't know what a leakdown test is?" Meant to help, not criticize, but it's obvious to me in retrospect that my wording was callous.

Stephan