I have a 1973 Plymouth Duster with a newer engine (I think we narrowed it down to an 80 something dodge at some point but don't remember). The car for the last few years has made an intermittent clattering noise, usually when held at a constant speed above 50MPH. I've never been able to get it to do it when holding the throttle in park, so I've never been able to troubleshoot. When I moved to a more mountainous area than West Texas' pool table flatness, I discovered it'd also happen while going uphill.

Tonight it started happening full time, so I got a screwdriver and used it as a makeshift stethoscope, and narrowed it down to the number 3 exhaust valve. The engine was overhauled under 50k miles ago by my dad and I, and everything has been more or less fine since. It has hydraulic lifters, and the noise in question is very similar to the noise made by the lifters when there's no oil, but a quick look under the filler cap while running tells me there's definitely oil in there getting to the lifters.

I'm afraid there may be something in the oil channel, or worse, the push rod is damaged, but I have no idea for sure. Any suggestions on what to try before I go and crack open the valve cover for exploratory surgery, or am I wrong entirely and is there nothing wrong?

The lifter could be collapsed, The quickest way to find out, is to take off the valve cover .



Dave

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81 Dodge D150
It looked easier in the book .

I don't think it would be...it's not backfiring or otherwise acting off. The only symptom is the noise. If the exhaust valve isn't working, I'd think that there would be backfiring/misfiring due to the valve not opening to allow exhaust out, and feeding that mess back into the intake.

A collapsed lifter won't keep the valve from opening as there isn't much travel available before the plunger bottoms out. The affected valve will just open late, close early and make noise.

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Joshua

Pull the valve cover and pinpoint the noisy lifter, then swap it out for a new unit.
Test the push rod to be sure the oil feed hole thru the center is clear. (or replace the push rod also)
Be sure to "pump-up" the replacement lifter in a cup of oil, before installing it.
DD