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Old 05-07-2020, 07:59 PM   #1
doug.nichols
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Smile First Compression Test

Just finished my first compression test. #1=58lb; #2=35lb; #3=58lb; #4=587lb. Any thoughts?
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Old 05-07-2020, 08:10 PM   #2
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Default Re: First Compression Test

Number 2 is low. Sorry, thats all I can offer LOL.
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Old 05-07-2020, 08:39 PM   #3
Jack Shaft
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Default Re: First Compression Test

One thing to try before a second compression test is to find a good straight stretch of quiet road,and run the car hard in second gear,then take your foot off the accelerator and let it pull down to idle in second gear,repeat four or five times..this forces the rings to work in both 'directions'..then take back to the shop and compression test while its still warm..
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Old 05-07-2020, 09:49 PM   #4
CWPASADENA
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Default Re: First Compression Test

I would think that #4 may be a little high,


or may be this is a typo?


Anyway, I agree with Jack and then repeat the test.


If #2 is still low, put some oil in that cylinder and retest. If the compression comes up, the problem is rings, If there is no or just a little improvement, the problem usually is valves and probably the exhaust valve.


If the problem is rings, continue to run the car and it may get better.


A bad valve will not fix itself.


Chris W.
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Old 05-07-2020, 09:50 PM   #5
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Default Re: First Compression Test

Valves
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Old 05-07-2020, 10:48 PM   #6
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Default Re: First Compression Test

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If your tests indicate valves, on the principle of check the easy things first, check the tappet clearances before you start tearing things apart.
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Old 05-08-2020, 01:58 AM   #7
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Default Re: First Compression Test

Hello
Sounds like a valve problem , try putting some oil in the low cylinder and see if it comes up, if it does them maybe a ring problem . But most likely a valve seat .
Dennis
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Old 05-08-2020, 06:03 AM   #8
Patrick L.
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Default Re: First Compression Test

LOL ! Yup, #4 reading is a tad high. LOL.

How has the car been kept or driven before you got it or how have you been driving since you got it ? If it has been sitting for awhile then continue to drive it normally for awhile and retest. If it has been driven right along then check the valve clearance and do leak test. The leak test can be done simply, nothing fancy. Just enough to see if there is a problem somewhere.
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Old 05-08-2020, 07:35 AM   #9
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Default Re: First Compression Test

#2 is low, now to find out why, you need to do a differential test and determine what's going on.
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Old 05-08-2020, 09:30 AM   #10
doug.nichols
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Default Re: First Compression Test

Thanks all. Good advice. (Yes #4 was a typo!)
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Old 05-08-2020, 03:07 PM   #11
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Default Re: First Compression Test

I had very similar results on my compression test. I ended up also doing a vacuum test and a leak-down test, both of which also indicated valve problems. Here's my thread for the leak-down test if you want to take a look:
https://www.fordbarn.com/forum/showthread.php?t=278957
Vacuum test:
https://www.fordbarn.com/forum/showthread.php?t=273571
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