Today I noticed a noise from my 79 that sounds very much like a valve tapping. It only happens with the car in gear, under acceleration. However, with the car in park, there is no noise at all...smooth idle as usual, and even revving it doesnt produce the dreaded "tapping" sound. Oil level is fine, and has been changed recently, pressure is OK, and the engine isnt running too hot. The tapping is uniform with the acceleration...i.e.-increases as rpms increase, decreases as they decrease. My question to those of you who are almost assuredly much more experienced than I am is: Does this sound like a valve train problem? Or is there something else I should check/look for?
Any insights or help would sure be appreciated.

Thanks,
John...

do you use roller rockers? they are know to make a slight ticking sound..

Check for any exhaust leaks at the manifold/header on the side thats making the noise. Sometimes a leak will mimic a noisy lifter.

Sarge

ok heres a list of things that may cause the tapping . loose rockers arms (i had to readjust mine when i purchased it and made a great improvement in lower noise as well as improved acceleration)withe the valve covers off you shouldn't be able to move any of them much at all by hand, some will be under load from the pushrod but some will not be and these should still have a very load on them,if you can wiggle them they all need to be adjusted. could also be wrist pins(oh no) they will make different noise under load than no load. not much you can do except rebuild. just keep the oil clean and no high rpms for this one. low grade offuel, causing pinging? too hot of a spark plug causing a early detonation, try colder plugs., check your timing too much advance, this would als only show up under load as a ping or litee tapping sound, main dearings also dound different under load than out of gear revving the engine up.

Thanks for all of the great responses. A little update. I went ahead and checked/reset timing. It was a few degrees off (no surprise). Also replaced plugs, wires, cap and rotor (since those were pretty old too). Flushed the oil with an engine cleaner, changed oil and filter too. After tuning everything, the car ran much better for a short period, but was still making the sound. Then performace seemed to degrade again, althought it runs generally OK. My guess is that something internal is amuck... Next step seems to be to pull the intake and heads, get a valve job done, and hopefully only have to do an "upper" rebuild. I suppose I can decide after I've pulled them, whether to go ahead with a short block rebuild as well, but imagine its best to do the whole shooting match. Any ideas or opinions on my plan of attack? Thanks again to all who gave inputs. I'll probably look for some advice on what cam/etc to go to since have to rebuild it anyway. Would like to improve it a bit if possible.
Thanks, JP

Your post states that you do not hear the noise until you are in gear. Before I started doing engine rebuilds, I would start looking closer at what changes " under load " when the car is put in gear. At this point, your noise may be coming from the transmission.
Look around for vacuum leaks also.
My car backfires when I take my foot off the gas. It does not mean I need engine work....I have a blown exhaust gasket.
Look around some more before you spend money chasing problems.

Thanks Glenn...

Good advice, and I've actually calmed down a bit. :) I suppose Im prone to the shotgun approach. But, I am planning on doing some stuff that I eventually would have done anyway. (ie-I want to put a slightly different cam, with new lifters, roller rockers). That would require replacing the intake gaskets of course, and I'll replace the exhaust gaskets as well. Also ordered a set of the correct vaccum hoses, new TVS valves, etc. I couldnt find a vaccum leak, but wanted to square the hoses away as they were old in either case. If its exhaust leak, intake leak, or vaccum, the above project should nail it...but I wont know until Im done.

As far as the Transmission goes...hmmmm...Hadnt thought it could be making the noise, as it sounded so much like a lifter. But, it does only do it when accelerating, and in gear/under load. If I back off of the throttle/cruise the tapping stops, or at least isnt audible in the cockpit. Would a speedo cable be suspect for making a clicking/tapping sound? Any idea what to look for in the Tranny? FYI, it doesnt slip at all, and has seemed to be trouble free. Also, no leaks anywhere on it.

Thanks,
John

I would think if your speedometer was causing the noise, you would see it relected in how the speedometer reads. ( like jumping around ). Disconnect it at the trans and go for a ride to see if the noise goes away.

I am having a issue that sounds alot like yours but I am thinking mines is possible in the rear drive line somewhere, someone said it was the the posi-trac but it only happens under load when taking off. I didn't have the problem till I had to do a radical manuver to keep a truck from t-boning me in the driver side door,I used 4 lanes getting it back under control at 75 mph.

But its another area that you might want to look at.

Sounds like an exhaust leak somewhere, they do sound like lifter noise when under load. Try taking a Screw driver about 10" long and placing the metal end against the valve cover and placing your ear to the plastic end of the screw driver while the motor is running (being careful of the fan) and you will be able to here the valve train much clearer. You can listen to all kinds of under the hood parts ,alt ,ac comp, etc. anything solid will normally work to transfer the sound.