Trying to find reason for miss

War Wagon

The War Wagon had a miss so I started checking it out. I pulled the plug wires one at a time and found that three cylinders were dead, made no difference in RPM's at all when the wire was pulled or all three at the same time for that matter. I pulled the plugs and checked to see if they were firing by laying them on the engine and turning over the engine and they were. Pulled valve cover and found the valves working OK. Did a compression test and found all cylinders down in the 60 to 70 PSI range, use to be 125 to 130 PSI before. I put some oil into the cylinders and the pressure only went up 10 PSI per cylinder. Hard to believe that all the valves are bad at once but who knows. The engine will start right up and smooths out when warm. The engine will hold 17" of steady vacuum at warm idle. Now where do I look next? Thanks for any input, Jim

BREK

try doing a cylinder leakage test. that will tell you for sure if it's in the heads or the rings.

War Wagon

Did a leak down test and have air out the exhaust, burn't exhaust valves I guess. I have heard of carbon build up holding the valves open. Jim

Holeshot

Hello. Is this a new or fresh engine? Did it run good ever? What about lifters holding the valves open? (loosen the rockers in question, recheck the leakage) Did it happen after an unusually high RPM blast? Also, did it happen after a new mod or somebody tweaking on something?

jeepsr4ever

sounds like a burnt exhaust valve

War Wagon

We had 130 PSI about a year ago, engine has almost 200,000 miles on it.
Zack was pretty hard on it at the ECI as you can see in the blown up TC
pictures. http://www.bulltear.com/forums/viewtopic.php?t=5358
We replaced the plugs and picked up one cylinder. We pulled the valve cover and checked the valves, springs, and rockers, everthing looked good.