Valve Adjustment - Type 4

[hambone]

Hiya, I'm advising this guy with a newly rebuilt engine that suddenly started running like crap after 10k miles. I believe it's a '75 bus.
He tells me that #3 valve is un-adjustable - he is unable to tighten down the set screw enough to make contact with the valve.

I am guessing a mushroomed adjuster head, a sunken valve seat, or rocker issues. Lifter maybe? You guys have any advice?

[SlowLane]

My guess: something blocking the valve open. Possibly (probably) a dropped valve seat.

Get in there with a good light and inspect/compare the installed heights of all the valves on that head. See if the culprit valve is further in (less height) than the other three. Remove rocker arms if necessary to get a clearer picture.

If that's the problem, shine a light down the spark plug hole and see if you can spot what's holding the valve open.

Free advice: worth every penny.

[Amskeptic]

Hiya, I'm advising this guy with a newly rebuilt engine that suddenly started running like crap after 10k miles. You guys have any advice?

Call the rebuilder.

Follow slowlane's advice. Do not crank the engine. Do not start the engine. A valve adjuster that cannot reach the valve stem is much less likely to be the usual litany of overheat symptoms that cause recession where you cannot back out the adjuster far enough to get clearance.
Do not rotate the engine into any resistance!
Colin

[hambone]

Thanks guys.