Compression test
Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
If you can pump up air pressure in the clyinders, one by one, and listen. If you here air from the carb or the exhaust, it is leaking past the valves. Air in the crank case, it is leaking past the rings. Air in the radiator, head gasket or crack in a water jacket.
Logistics Pro
Joined: Oct 2005
Posts: 3,785
Likes: 4
From: Mddl A MexCans
Leak Down poor man style (ungauged)
This is from another thread but reposted here out of caution and better detail.
Caution: Keep hands etc away from fan and pulleys etc.. As the engine will turn with a sharp burst if the engine is not at TDC for that cylinder.
All plugs removed. While testing have the breather and radiator cap off.
My advice as it's not mentioned: Set the supply of air to 60lb
Set the engine at TDC for #1 after number 1 has been tested rotate the engine in normal operating direction 90 deg and check the next cylinder in the firing order (15426378)
Air coming through the carb = intake valve leaking
Air coming through the exhaust = exh valve leaking
(If either valve is leaking be sure it's at TDC on comp stroke)
A head gasket leak will show up as air leaking out the adjacent cylinder or through the radiator filler neck cracked cylinder wall or head will also show as leaking through the radiator filler neck
A leak in the rings area will show up as air coming through the oil breather cap or dipstick tube.
OK hope that helps .. BOL, Bob
Caution: Keep hands etc away from fan and pulleys etc.. As the engine will turn with a sharp burst if the engine is not at TDC for that cylinder.
All plugs removed. While testing have the breather and radiator cap off.
My advice as it's not mentioned: Set the supply of air to 60lb
Set the engine at TDC for #1 after number 1 has been tested rotate the engine in normal operating direction 90 deg and check the next cylinder in the firing order (15426378)
Air coming through the carb = intake valve leaking
Air coming through the exhaust = exh valve leaking
(If either valve is leaking be sure it's at TDC on comp stroke)
A head gasket leak will show up as air leaking out the adjacent cylinder or through the radiator filler neck cracked cylinder wall or head will also show as leaking through the radiator filler neck
A leak in the rings area will show up as air coming through the oil breather cap or dipstick tube.
OK hope that helps .. BOL, Bob
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Senior User
Joined: Sep 2006
Posts: 261
Likes: 0
From: Heart of Ga.
Thanks for the info guys. I have oil coming from the breathers and I've posted a question on this already, but was hoping it was from heads not the block. I'm thinking a full rebuild is in order.
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Senior User
Joined: Sep 2006
Posts: 261
Likes: 0
From: Heart of Ga.
Originally Posted by Redmanbob
Oil coming from the breathers ? I looked for the thread but unsuccesful finding it...breathers being the cap for the PCV and intake to crankcase (atop the valve covers) ?
Logistics Pro
Joined: Oct 2005
Posts: 3,785
Likes: 4
From: Mddl A MexCans
I have seen several threads on this... so take a look around. As I recall a few things to look into are
1. PCV (hose and valve working and correctly routed- vent side not clogged)
2. Returns for oil at rear of the heads clear
3, CRS sorry...
1. PCV (hose and valve working and correctly routed- vent side not clogged)
2. Returns for oil at rear of the heads clear
3, CRS sorry...
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Postmaster
Joined: Jul 2005
Posts: 3,248
Likes: 0
It look like you got bad rings on the pistons, what are the compression numbers.
Is there any blue smoke coming out of the exhaust?
Is there any blue smoke coming out of the exhaust?
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Senior User
Joined: Sep 2006
Posts: 261
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From: Heart of Ga.
Pulled the heads today, I got some bad valves! The block appears okay. Got a neighbor who is a mechanic and a friggin' Ford guru to have a look and I'm going to rebuild the top end. A couple of lifters had not been Rotating so they are "cupped", so I will put new cam and lifters in as well.
looks like it's going to be not much hassle at all. Thumbs up!!
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