Help with Compression check
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Senior User
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Help with Compression check
I did a compression check on my 337 flathead. This is what I got.
#1 - 130
#2 - 120
#3 - 122
#4 - 130
#5 - 0
#6 - 0
#7 - 130
#8 - 130
I squirted some oil into cylinders 5 and 6. I still get zero compression on those cylinders. Because both cylinders are side by side, I am guessing that it may be a bad head gasket or maybe a crack somwhere. I think I can rule out rings and valves. I would appreciate some input from the group on what it could be or where to look. I didn't find anything useful in the archives.
Thanks,
John
NNY
#1 - 130
#2 - 120
#3 - 122
#4 - 130
#5 - 0
#6 - 0
#7 - 130
#8 - 130
I squirted some oil into cylinders 5 and 6. I still get zero compression on those cylinders. Because both cylinders are side by side, I am guessing that it may be a bad head gasket or maybe a crack somwhere. I think I can rule out rings and valves. I would appreciate some input from the group on what it could be or where to look. I didn't find anything useful in the archives.
Thanks,
John
NNY
Senior User
Joined: Apr 2003
Posts: 209
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you are more than likly right thinking head gasket
pull off the head and have a look
I had the same problem but my problem was that both exaust valves got moisture in them beeing the shared the same exaust port they just hung open look through your spark plug holes and make sure they arn,t stuck open before pulling of the head
good luck
pull off the head and have a look
I had the same problem but my problem was that both exaust valves got moisture in them beeing the shared the same exaust port they just hung open look through your spark plug holes and make sure they arn,t stuck open before pulling of the head
good luck
Post Fiend
Joined: Mar 2004
Posts: 24,418
Likes: 3
From: San Francisco, Ca.
I'm thinking stuck valve(s).
I would think that squirting oil will just seal the piston rings; not the valves IF they are stuck in the open position.
Even with a cracked head/block, or bad head gasket, I would think you would get some sort of reading.
Still, does sound unusual to have both #5 and #6 cylinders with a zero reading.
I would think that squirting oil will just seal the piston rings; not the valves IF they are stuck in the open position.
Even with a cracked head/block, or bad head gasket, I would think you would get some sort of reading.
Still, does sound unusual to have both #5 and #6 cylinders with a zero reading.
Last edited by sierraben; Apr 15, 2006 at 04:27 PM.
Fleet Mechanic
Joined: Jun 2004
Posts: 1,757
Likes: 37
From: Minnesota
Squirt some penetrating oil into the cylinders fog them really good and try again the next day. This may also give you a clue as to where the air is going might get someone to listen to the tail pipe as you squirt.
Junior User
Joined: Feb 2003
Posts: 89
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From: southern New Hampshire
Our 59 223 6 cyl stararted running poorly last week after sitting a while. I thought it may have jumped timing, but did a compression check and found #1 cyl had almost no compression. I was ready to pull the head thinking a blown head gasket when I remembered I had bought a special hose adapter last year that has a spark plug fitting on one end and a connection to an air hose on the other end. I found the intake valve was just bearly sticking open (air blew up thru the carb when both valves closed). I squirted some Marvel Mystery Oil into the spark plug hole, replaced the plug and started the engine. it ran fine until I let it cool done and started it again with the same problem. I believe my problem is a result of unleaded gas and the valves not getting the lead lubrication they were designed for.
Dan
Dan
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Posts: 21,955
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From: Rio Rancho, NM
John,
I'd check for the valves being stuck open also
Dan,
Sounds like things are carboned up a bit. Has it not been drivin hard all winter? Not driven enough tto really get warmed up and the choke all the way off? Unleaded fuels wouldn't have anything to do with that. You might try getting the engine up to operating temp and slowly pouring small amounts of water into the carb with it running about 2000 to 2500 rpm or so. Don't pour in enough to kill it. This will do wonders to cleaning out the carbon (anyone remember the old water injection systems??) Either that or take it out and drive it hard, rev the tar out of it and see if you get ugly clouds of a brownish smoke. (don't blow it up though)
Good luck
Bobby
I'd check for the valves being stuck open also
Dan,
Sounds like things are carboned up a bit. Has it not been drivin hard all winter? Not driven enough tto really get warmed up and the choke all the way off? Unleaded fuels wouldn't have anything to do with that. You might try getting the engine up to operating temp and slowly pouring small amounts of water into the carb with it running about 2000 to 2500 rpm or so. Don't pour in enough to kill it. This will do wonders to cleaning out the carbon (anyone remember the old water injection systems??) Either that or take it out and drive it hard, rev the tar out of it and see if you get ugly clouds of a brownish smoke. (don't blow it up though)
Good luck
Bobby
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Fleet Mechanic
Joined: Dec 2005
Posts: 1,601
Likes: 44
If the above dont work try this , get the bad one with piston up, both valves
closed both spark plugs out, and stick a shop vac in the exhaust pipe on the
blow side then hear if it comes out of the next bad hole or the carb, make sure
the throttle is wide open, then turn the motor over, and you can hear at least
what the valves are doing. I call this method the backward approach
sam
closed both spark plugs out, and stick a shop vac in the exhaust pipe on the
blow side then hear if it comes out of the next bad hole or the carb, make sure
the throttle is wide open, then turn the motor over, and you can hear at least
what the valves are doing. I call this method the backward approach
sam
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