I posted last week about my 78 Bronco I bought with a ton of running problems but almost had them ironed out. Turns out what I waited to do last I should have done first - a compression check. Cyl #5 is dead, 0 compression. Wet test doesnt change a thing. The plug doesnt have any oil on it but it is wet with fuel. I pulled the valve cover to look at the springs and turned the motor over to confirm the valves were opening and closing and the y were. When I got the truck, the header gasket on this head was completly blown. I have no idea how long the previous owner drove it like this. Is it possible a blown gasket could have caused a burnt valve? Since the plug isnt oil soaked can I assume the bootom end is still intact? Thanks for any help.

 

0 compression is usually a pretty good indicator of a burned valve(s) and since you already checked to see if the valves were moving then it's almost a sure thing. If it were a holed piston you'd be getting excessive crankcase pressure, i.e. oil out the dipstick, etc. How the valve(s) got burned is anybody's guess. Sounds like the heads need to come off.

 

These heads are bad for burning valves, Ive had two.

Nathan

 

Thanks for the input. I'll pull the heads and have them redone. I'll let you all know how it works out. Thanks again.