1951 239 Compression
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
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 I’m 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 .
ive driven the F3 a couple times around town already and today i finnalh decided to do a compression test .
now I’m 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 .
Fleet Owner
Joined: Jul 2004
Posts: 27,299
Likes: 1,059
From: NM
#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?
Just to clarify, were all the plugs out? Throttle open?
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
#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?
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 .....
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
#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?
Just to clarify, were all the plugs out? Throttle open?
and I didn’t do the test 1-8.
I did 5,6,7,8 first then 1,2,3,4
Senior User
Joined: Jun 2018
Posts: 201
Likes: 0
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 60’s 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
Take out all of the plugs and recheck the compression with the throttle open. My compression whent from the 60’s 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
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
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 60’s 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
Take out all of the plugs and recheck the compression with the throttle open. My compression whent from the 60’s 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 I’ve 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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Senior User
Joined: Jun 2018
Posts: 201
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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 I’m curios to see how the compression looks hot compared to cold.
-Chris
in my case, my truck has hot starting issues so I’m curios to see how the compression looks hot compared to cold.
-Chris
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Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
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
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
Fleet Owner
Joined: Jul 2004
Posts: 27,299
Likes: 1,059
From: NM
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.
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
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 it’s 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
Thread Starter
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Mountain Pass
Joined: Nov 2017
Posts: 194
Likes: 2
From: Toronto, Canada
glad to hear that , just had the carborator rebuilt and generator rebuilt. Truck is running ok but sometimes it’s 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
