lost comprsion on a cylinder or two any ideas 2000 454 mag
#11
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Joined: Jan 2001
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From: ST. Louis, MO, USA
Possible overheat and low compression on 2 adjacent cylinders, sounds like head gasket. Not too big of a job. Pull all plugs and run a leakdown.
#12
Head gasket between center cylinders is my guess
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#14
Some good info about compression and compression leakdown tests/testers in this thread.
http://www.offshoreonly.com/forums/s...d.php?t=106452
Dave
http://www.offshoreonly.com/forums/s...d.php?t=106452
Dave
#15
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Joined: Jan 2001
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From: ST. Louis, MO, USA
If you dont have a leakdown tester (I suspect you dont since you're asking), but do have a compression guage, do this.
Turn engine so that low psi cylinder is at TDC compression, valves must be completely closed. Use your comression guage hose to pressurize cylinder to around 50psi. Now listen to where the air is coming from.
If it's from the adjacent cylinder, you've got a bad head gasket. If from the intake/carb or exhaust, it's a bad valve. If from the breather, it's going by the rings. If from the blocks water jacket, cracked head or head gasket.
Gary
Turn engine so that low psi cylinder is at TDC compression, valves must be completely closed. Use your comression guage hose to pressurize cylinder to around 50psi. Now listen to where the air is coming from.
If it's from the adjacent cylinder, you've got a bad head gasket. If from the intake/carb or exhaust, it's a bad valve. If from the breather, it's going by the rings. If from the blocks water jacket, cracked head or head gasket.
Gary
#16
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Joined: Nov 2002
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From: ankeny,ia.
Originally Posted by Gary Anderson
Use your comression guage hose to pressurize cylinder to around 50psi. Now listen to where the air is coming from.
You'll need to remove it.
#17
I appreciate all the info guys, keep it coming , I am tearing it down now, and redid comp test and the outside had 125 on all 4 and the inside had 125 on front 112 on 2nd, 45 on 3rd, and 125 on fourth



