Hello all. I have a 1997 f superduty dump truck with the 460. Has 35600 original miles. Just bought the truck and ran great for about two weeks. All of a sudden had a light misfire at idle when cold. Changed plugs and wires thinking maybe it just needed a tune up. Within a couple hundred miles Truck just ran worse and worse misfire all the time and loss of power.

Here is is what I’ve done:

compression checked all cylinders. 1-7 showed 130 psi number 8 showed 0. The weird thing is upon First stroke of number 8 cylinder it showed 120 psi then lost it all. If Truck sat for a minute same thing. Plug had oil on it when pulled

did a leakdown test: piston tdc did not hear any air out of exhaust or intake. Did however hear it from the oil fill in valve cover

truck is smoking from the exhaust (think it’s burning oil)

added bg engine restore. Drive around for about 30 miles and then changed oil and added bg MOA. Also added a little mystery oil to the oil and gas. Seems to idle and have a little more power back but still very rough.

Any ideas? Options thrown out have been a valve issue or bad ring. Any ideas on cost to repair or how I should go about?

Thanks!

 

Pull the valve cover and see it the valves are moving. Could be a burnt piston.

 

Yep, take valve cover off first and take a look. If it all looks ok then take the rockers off that cylinder and check the valve guides.