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09-17-2013, 05:48 PM | #1 |
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SHOCKED With Compression Check
Today, I decided to check the compression on my newly rebuilt (462 miles) motor. I wanted to have something to have as a base for any further checks. The results SHOCKED me because they are #1 - 20 lbs., #2 - 25 lbs., #3 - 27 lbs., and #4 - 28 lbs. Could it be that the rings are not seated? Or is there some other reason? Give me some good news!
Thanks for your time. Cape Codder |
09-17-2013, 05:54 PM | #2 |
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Re: SHOCKED With Compression Check
Did you open the throttle all the way? Maybe the tests were skewed for lack of intake volume.
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09-17-2013, 05:59 PM | #3 |
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Re: SHOCKED With Compression Check
Open throttle wide open, crank until it won't climb any further, do it motor hot.
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09-17-2013, 06:01 PM | #4 |
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Re: SHOCKED With Compression Check
good news cape,
go get yourself a quality gauge and deep six that one. opening the throttle never made much of a difference for me and definitely will not cause a loss of 50% compression reading plus your car would be running like dog poo Last edited by Mitch//pa; 09-18-2013 at 02:20 PM. |
09-17-2013, 06:05 PM | #5 |
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Re: SHOCKED With Compression Check
If it runs good I would be looking at the compression tester.Sometimes raw gas and oil gets up into the tester and gums things up while they sit in the toolbox.Unseated rings and low air volume will change numbers,but not to the kind of numbers you have.A few pounds off is one thing,but 30-40 pounds is another.You may have some tight valves being it is a new engine,but I would think it would be showing other symptoms.What made you feel you had to check the compression? Was something acting up?
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09-17-2013, 06:24 PM | #6 |
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Re: SHOCKED With Compression Check
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09-17-2013, 06:59 PM | #7 |
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Re: SHOCKED With Compression Check
I second the suggestions to try another compression tester. To have all 4 that low, but so close to each other seems odd.
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09-17-2013, 07:19 PM | #8 |
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Re: SHOCKED With Compression Check
were all the plugs out when u did this? they should be
Agree obtain another tester and compare
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09-17-2013, 07:42 PM | #9 |
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Re: SHOCKED With Compression Check
Cape Codder, Why do you need a "BASE" for further tests?? If it's running good, leave it alone!
PROPER compression tests should be left to techincians that know their stuff & have done this for years & know how to analyze the results properly. Compression tests are generally only necessary to diagnose problems. Some folks "tinker" too much, if you must "tinker", adjust your horn, check your oil & water, check tire pressure, & check your lug nut tightness, bathe your rubber chicken, scratch your butt, etc. Bill W.
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09-17-2013, 07:59 PM | #10 |
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Re: SHOCKED With Compression Check
Use a compression tester like the one I use. Most people have a set of them.
I use my right thumb. |
09-17-2013, 08:14 PM | #11 | |
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Re: SHOCKED With Compression Check
Quote:
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It's not what people think they know that will hurt them, it is what they think they know that aint so! -Mark Twain. It is the very things that we think we know, that keep us from learning what we should know.- Unknown |
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09-17-2013, 08:31 PM | #12 | |
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Re: SHOCKED With Compression Check
Quote:
It's just like preventive maintenance beats having to do repairs. |
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09-17-2013, 08:40 PM | #13 |
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Re: SHOCKED With Compression Check
QGolden, We're NOT workin' on aircraft or rockets, just a FUN old SIMPLE Model A.
It's apparent that Cape Codders tests were NOT done properly, with that low a compression, it wouldn't even start & run. Bill W.
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09-17-2013, 10:20 PM | #14 | |
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Re: SHOCKED With Compression Check
Quote:
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09-17-2013, 11:08 PM | #15 |
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Re: SHOCKED With Compression Check
I agree with Bill W, it would not even run with compression that low
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09-18-2013, 12:17 AM | #16 | |
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Re: SHOCKED With Compression Check
Quote:
I feel that an apology is in order to the novices & the seasoned Model A folks who DO know how to make a Model A run as well as it did when it was new! (And sometimes BETTER, even on a stock Model A!) Bill W.
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"THE ASSISTANT GURU OF STUFF" Last edited by BILL WILLIAMSON; 09-18-2013 at 12:29 AM. |
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09-18-2013, 06:59 AM | #17 |
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Re: SHOCKED With Compression Check
Hi Bill,
I presume your reply was made in jest? Nothing Marco said was derogatory. I'll bet you lunch that the folks who keep their A's "running as new", spend a lot of time benchmarking their engines.
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It's not what people think they know that will hurt them, it is what they think they know that aint so! -Mark Twain. It is the very things that we think we know, that keep us from learning what we should know.- Unknown |
09-18-2013, 08:01 AM | #18 |
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Re: SHOCKED With Compression Check
Yep, not only do most of these cars not run like a "rocket", the vast majority don't even run like a Model A should.
How true that statement is. I owned a Model A for a few years before I really learned how to maintain it properly. And drive it properly. Now that I have gained this knowledge I can easily tell a good runner from one with problems. Bill, you know if someone wants to establish a compression baseline on their motor, why not? It's cheap and keeps them out of the bars! Of course I do agree to try it with a known, good compression guage. I think it will come in significantly better than his current readings! |
09-18-2013, 08:04 AM | #19 |
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Re: SHOCKED With Compression Check
Yes the readings are low, but the consistency between them all is a good thing. Try squirting a little oil in the cylinder and doing it again.That could tell you if its a ring issue.
I really hope Marco and Bill are just shining each other on.... I love the information but I can do without the drama. |
09-18-2013, 08:09 AM | #20 |
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Re: SHOCKED With Compression Check
Marco's right. Once you hear and feel how good an original low mileage engine runs, you'll find there aren't many that can match it. So many have some noise or vibration that wasn't there from the factory.
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