Clacking in valvetrain

[73ChargerSE]

I've got a '72 Duster with a 340 in it.  The motor's got a clacking sound on the #6 cylinder on the intake side.  If you put quite a bit of pressure on the rocker on top of the valve, the clacking goes away and seems to run a bit better.  We took out the lifter and cleaned it out.  After putting it back on, nothing changed.  What could be causing this? We're trying to sell the car and the noise is very unattractive.

Thanks!
Paul

[RD]

lifter could have collapsed on the inside.  replace the lifter.  check the rocker to make sure that the mating point between the pushrod and the rocker shows no unnatural wear.

[73ChargerSE]

How can you tell if the lifter has collapsed?  We took the lifter apart and cleaned it pretty well.  When we took it out it was hard as a rock.

[flyinlow]

Sounds like a bad lifter.

[Sublime/Sixpack]

How many miles are on the 340's valve train?

[73ChargerSE]

I'm actually unsure of that.  When I took off the valve cover everything looked VERY clean.  The valve seals were still intact and everything.  The keepers looked new as well.

[firefighter3931]

If the lifter is not collapsed and the valvetrain is still noisy then the cam could be going flat on that lobe. How did the lifter face look ? Any signs of uneven wear ?

I would do as Jamey (RD) suggested and replace the lifter. Treat it like you would any new cam/lifters and breakin at 2500 rpm for 20 minutes and use good oil and an additive like EOS or ZZDP+



Ron

[RD]

How can you tell if the lifter has collapsed?  We took the lifter apart and cleaned it pretty well.  When we took it out it was hard as a rock.

do you mean you could not push down the internals of the lifter with a pushrod?  if there is no movement of the hydraulic mechanicals of the lifter itself, the lifter is bad.  if the internal hydraulic mechanicals have too much give, the lifter is bad.

the only reason as to why your "clacking" sound would happen are:

1) worn cam lobe
2) bad lifter
3) pushrod installed is too short or damaged
4) rocker arm assembly damaged/worn
5) rocker arm shaft not torqued to specification