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1951 239 Compression

  #1  
Old 07-10-2018, 11:22 PM
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1951 239 Compression

Tip and Hints required.

ive driven the F3 a couple times around town already and today i finnalh decided to do a compression test .
now Iím a little worried .
i thought she was running ok but the results of the compression are not what I expected .

1- 34lbs
2- 60lbs
3- 55lbs
4- 70lbs
5, 6,7,8. - 91lbs
whag do You experts think .


 
  #2  
Old 07-10-2018, 11:55 PM
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#1 is likely a bad or sticking valve. May improve as you drive it some more. Did you do them from #1 thru #8? because it's almost a linear upward trend, which could be from worn cylinders getting coated with oil as you crank it.

Just to clarify, were all the plugs out? Throttle open?
 
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Old 07-11-2018, 06:19 AM
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Originally Posted by ALBUQ F-1 View Post
#1 is likely a bad or sticking valve. May improve as you drive it some more. Did you do them from #1 thru #8? because it's almost a linear upward trend, which could be from worn cylinders getting coated with oil as you crank it.

Just to clarify, were all the plugs out? Throttle open?

no I did one plug at a time. All other plugs installed
and just pushed starter button no throttle .....
 
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Old 07-11-2018, 06:43 AM
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Originally Posted by ALBUQ F-1 View Post
#1 is likely a bad or sticking valve. May improve as you drive it some more. Did you do them from #1 thru #8? because it's almost a linear upward trend, which could be from worn cylinders getting coated with oil as you crank it.

Just to clarify, were all the plugs out? Throttle open?


and I didnít do the test 1-8.

I did 5,6,7,8 first then 1,2,3,4

 
  #5  
Old 07-11-2018, 06:59 AM
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I am sure Ross is still sleeping. 'Tis early where he is. Run the compression test as he suggests. Get the engine warm.
 
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Old 07-11-2018, 08:56 AM
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Check out a recent thread of mine about low compression.

Take out all of the plugs and recheck the compression with the throttle open. My compression whent from the 60ís to over 100 when I did the test correctly.

I also would not downplay a easy oil change if you have not done that yet.

-Chris
 
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Old 07-11-2018, 09:23 AM
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Originally Posted by 1954wrecker View Post
Check out a recent thread of mine about low compression.

Take out all of the plugs and recheck the compression with the throttle open. My compression whent from the 60ís to over 100 when I did the test correctly.

I also would not downplay a easy oil change if you have not done that yet.

-Chris

Thanks Guys.
I will Redo again The way you guys are saying
I just recently did the first oil change since Iíve had it
I wanted to get at Least 500 miles before changing it again ...

should i run the truck and let the engine get hot before the compression test ?

 
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Old 07-11-2018, 09:39 AM
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I would start cold and then do it again hot if you still have questions.

in my case, my truck has hot starting issues so Iím curios to see how the compression looks hot compared to cold.

-Chris
 
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Old 07-11-2018, 10:52 AM
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Make sure the battery is charged up before starting the test.
 
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Old 07-11-2018, 12:13 PM
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Originally Posted by ALBUQ F-1 View Post
Make sure the battery is charged up before starting the test.

im still on 6v. I might have to do it in stages to get the proper readings .

thx you
 
  #11  
Old 07-11-2018, 12:44 PM
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Your battery will last a lot longer with the plugs removed.
 
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Old 09-23-2018, 11:30 PM
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So I finally got a chance to re run my compression test
my results were a lot better with all the plugs off

1 - 95 5 - 101
2 - 81 6 - 82
3 - 86. 7 - 90
4 - 96 8 - 78

The Old Flat head Sounds Tired

what do you guys think of these numbers
 
  #13  
Old 09-23-2018, 11:59 PM
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Seems like some of the cylinders are tired, but not badly enough to rebuild if you are just using it for occasional around-town trips. Driving it some more, getting it thoroughly warmed up and giving the rings a chance to free up, may improve the numbers significantly.
 
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Old 09-24-2018, 12:41 AM
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Originally Posted by ALBUQ F-1 View Post
Seems like some of the cylinders are tired, but not badly enough to rebuild if you are just using it for occasional around-town trips. Driving it some more, getting it thoroughly warmed up and giving the rings a chance to free up, may improve the numbers significantly.

glad to hear that , just had the carborator rebuilt and generator rebuilt. Truck is running ok but sometimes itís stutters a bit. Just seen a really bad exhaust leaks in the manifold ..
would that cause the truck to stutter ?

here is a pic of my manifold hole. Gonna change it up to headers and dual exhaust it was covered up by an old piece of tin LOL
 
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Old 09-24-2018, 09:21 AM
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Originally Posted by Old51f3 View Post



glad to hear that , just had the carborator rebuilt and generator rebuilt. Truck is running ok but sometimes itís stutters a bit. Just seen a really bad exhaust leaks in the manifold ..
would that cause the truck to stutter ?

here is a pic of my manifold hole. Gonna change it up to headers and dual exhaust it was covered up by an old piece of tin LOL

 

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