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Old 10-21-2012, 10:30 PM
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Air Randy Air Randy is offline
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Join Date: Aug 2008
Location: Franktown, CO
Posts: 2,852

From reading your initial post and compression readings, it is very doubtful you have "bad" valves. Depending on how many miles the motor has on it, you may be losing a little compression from worn valve seats but nothing serious. Adjusted for the altitude you are getting 125 psi compression average and all of the cylinders are within 10% of each other. This motor only had 150 psi brand new from the factory, so you are still well within the normal range, especially since the readings were taken cold.

Chasing compression issues is what you do if you're burning serious oil, losing radiator water and/or have compression readings of 20 psi or 0. Unless you have oil in your water or water in your oil, I don't see anything to indicate a head gasket leak. As stated above, it doesn't sound to me like your valves are bad or your piston rings are seriously worn.

Before I do anything else, I would change the valve cover gasket and get the motor cleaned off. Oil on your spark plugs wires/boots can cause them to short and you will lose power.

Next, check what type of plugs are in the rig. You should replace them if you don't know how old they are and look at the heat reading. If you are seeing any signs of fouling step up one heat range.

Next, check your timing. If that is set correctly and you still feel down on power, it is most likely a fueling problem. If that motor has injection on it then there are several sensors that may need to be checked to make sure it is fueling correctly.
Randy Rosetta KDKWX TLCA #19351 NOW 2015 Rubicon Hard Rock & (2) 1970 Boss 302 Mustang's THEN 69 FJ40 Buggy "Meanie", Mini-truck "Gecko" & 74 FJ40 "Blue Mule"
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