Hello all. First off, happy to be here! I just purchased a 1968 F-100 and I've spent the last 2 weeks browsing upwards of 50 threads anonymously on everything from wire diagrams to bushing replacement. There's a ton of great knowledge here.

Now for the meat. It came with one major issue - a tapping noise coming from what seems to be inside the driver side valve cover. I've taken the valve covers off and didn't see anything out of the ordinary, There was some gunk built up due to it being an older truck and the fact that it's been in storage for a while. I've changed the oil (10w-40 recommended by the guy at napa) and added a quart of Lucas oil treatment. The issue hasn't gotten any better so I'm looking for some input.

I'm assuming its a lifter or push rod but there are a few anomalies. The sound isn't present at idle unless the truck is warm and has been running/sitting in park for 10 minutes. Slight pressure to the gas pedal - no noise. Slightly more pressure - noise. Slightly more pressure than that - no noise. it comes and goes depending on throttle pressure which might be normal for this type of issue but I'm new and still learning about all this. It seems a little weird to me that it's not consistent.

As a side note, the power steering pump is inoperable. The aftermarket Bosch oil pressure gauge reads nearly 50 psi when cold and closer to 25 when warm. And the guy before my put a new double barrel Holley carb on it (I found out the hard way he didn't reconnect the kickdown linkage and just left it floating).

Any ideas? Is it simply pull the heads and replace the lifters and push rods? I ordered a new vacuum advance and plan to change to plugs here soon. I appreciate any feedback.

 

You do not have to pull the heads to do a cam and lifters, just the intake. Does the intensity of the tick change, louder when idle and off idle? The second question is about the oil pressure, is it 25psi at idle when hot or at speed? I am not sure about putting new lifters on a worn in cam, I would replace the timing chain, cam and lifters if it were me.

 

Sorry @fe390pc that was definitely an accident. I meant intake but the more I think about this the more potential I feel it has to turn into a full rebuild. I just wanted to fix the tap and get some more (safe) miles out of it before winter. If I'm all the way down to changing the cam then I feel like your just a few steps away from pulling the engine and getting it ported and polished. I might be being a little dramatic there though.

The intensity of the tick changes significant under throttle. But while warm and after sitting for a while the tick seems somewhat consistent if not very loud.
The 25 psi is hot and at speed.

 

I agree a rebuild may be your best option!

 

Before doing any of that a couple of things…

First, are you two hundred percent certain that it’s coming from under the valve cover and there’s not an exhaust leak nearby?
While the changing tone and intensity with different throttle positions isn’t unheard of with a lifter, it’s a sure bet that exhaust leaks do that quite often.

Second, oil additives can work very well, not every time unfortunately, but they can work well.
However they rarely work instantly on an old engine. Might take two or three oil changes to get it to start going away.
That’s what happened on my 71. Three or four consecutive oil changes with flushes and repeated applications of cleaning additives completely got rid of my smoking, oil usage and lifter ticking.

I had what I thought was a transmission problem once.
Every time I put the three on the tree shifter into reverse I would get a fairly loud ticking sound from underneath.
Turned out to be a loose spark plug in the number eight position and my shift lever arm was pushing the plug wire just enough to open up a leak.
That compression leak was the first time I’ve ever heard that type of noise associated with a leak. But since then have heard plenty of them with exhaust leaks.

 

Oh, and those oil changes in my 71 302 were not regular oil changes. At only $.89 a quart back then I figured I could afford doing it more often to see if it would work.
So I did those three or four changes between 1500 and 2500 miles each.
Went a lot quicker that way.😉😁

 

I have a 300 4.9L inline 6 in my 72 F250 and run Rotella T4 15W-40, it has the most zinc of any off the shelf oil and no additive needed.

Budy of mine has a 69 240 F100 that had a ticking lifter, drained his oil & filled with Rotella T4, for now no more tick. Might want to try the same. It's a cheep fix if it works. Even if it does not fix the problem it is a very good oil for our old motors. Better than additives.

 

I chased a lifter tap on an FE engine for months...turned out to be a push rod would occasionally rub the oil splash shield under the intake. Probably not the OP's problem but worth checking.

 

Thanks for all the feedback guys. If it's not the exact cause, chances are it's still worth taking a look at regardless. I'll make sure to be thorough about it. It does seem to be originating from the top rear driver side of the engine. Quieter when I'm underneath and on the passenger side. I think I'll just pull the intake and take a good look at all my rods and lifers and make sure all my oil passages are nice and clear. I'm also going to do a quick compression test and change the plugs while I'm at it.

On a lighter note. I got the radio working without starting a wiring harness fire and changed the vacuum advance which made it start and run noticeably better. So there's that at least.

 

Hey, those are both wins in any category!

 

Might try a automotive stethoscope to chase it down. I got one from fleabay for $10.
Also check the fuel pump, another common tick on a FE from the eccentric and FP arm.

 

That is what I was thinking, exh leak between manifold and head, could be on the bottom side and not be seen, or between manifold and head pipe.
More than once this type of leak has been thought to be a bad lifter and it was not.

I also think this as it changes as the motor get hot.
The exh manifold expands as it gets hot and you now have a leak or it gets louder.
Can have someone with a rag cover the tail pipe when it is making noise and see if it changes.

What is the hot engine oil psi at idle that is the real question?
Dave ----