I'm going to check the pushrods tomorrow to be sure

 

I adjusted the valves with the engine running, but the sound is still there.[/QUOTE]

[QUOTE]

That eliminates the valve lash as a source of noise then.

 

One more "guess" then I give up.

Years ago I had a distributor for unknown reasons make a ticking sound at idle. I don't recall if the rotor was actually striking a brass terminal in the cap or just a loud arcing spark jump. Maybe carbon tracking?
Tick-tick-tick every time the rotor came around to that side of the cap.

It will cost you nothing to have a look-see under the cap.

 

The distributor is as good as new.
I checked it to be sure, but no carbon.

 

Did you pull the distributor and check for end play? I'm telling you that was the clicking noise in my 77.

 

Yes I did that.

 

Could be so many different possibilities! Couple other long shots, it looks like you used new bolts on your intake....make sure that none of them are a tad too long coming through the head....one of your pushrods could be hitting the bottom of said bolt. Another idea, take off all drive belts and run it just for a handful of seconds, this will rule out anything bolted to the front of the engine. Pull the dipstick up 6 inches, making sure that's not getting struck. If you have another distributor, try it, the stock one in my '78 made noise like the previous poster's '77. Cracked porcelain on a spark plugs or melted wire, like suggested is also possible, triple check. Go over the headers one more time, also making sure the collectors aren't leaking. I will continue to ponder on this! One last thing, on the fuel pump rod, I've always used a dab of grease from the the grease gun, put it on the tip of your index finger and put in the hole for the fuel pump rod, then install the rod....the thicker grease will hold it up in place while installing the fuel pump, start with one bolt which can now be used as pivot point, swing the other side of the pump up and install the second bolt. Piece of cake! Good luck 👍

 

Thank you for your detailed explanation and tips.

The intake bolts are the same length as the old bolts.
I have already run the engine without all the drive belts.
I tried another distributor, but that did not help either.
The spark plugs are all new and the spark plug wires are also in good condition.
I have checked everything for leakage and sound several times, but cannot trace the sound.

 

I would like to come back to this.
My distributor has an end play of 0.025.
Now I have studied this further and read that it must be between 0.002 and 0.007.
What do you advise?

 

Did you check for an exhaust leak throughout the entire system?
I had an exhaust leak at the header collector once and it drove me crazy.
Check around all the welds and slip joints.
Could it just be a sticky lifter?
If you are in the valve train anyway, you might check them and just put in a new set.
If you know someone with a lift, put it up in the air and listen along all the exhaust and around the pan.
If the pan was replaced when it was rebuilt, it might be a slight rod to oil pan interference, especially if new rods were installed or if the engine was stroked.
Does the ticking noise go away or change when the engine warms up?

 

Aluminum housing HEI ?
0.015" - 0.020" ... I wouldn't sweat what you have now ... that 0.002"-0.003" will likely shrink when hot and break your heart.

-add-
jeez ... dunno ... but maybe the pump itself is noisy ?

 

I checked the entire exhaust from the exhaust manifold to the end.
I've had the Corvette on a bridge and checked everything from top to bottom with a hose.
I have checked the lifters and the camshaft.
The tapping is cold the same as with a warm engine.

 

Thanks for your comment.
I have indeed a aluminum housing HEI.
0.010 to 0.020 is good for a aluminum housing?

The oil pump is new.

 

Considering your going Mad with this tick. I'd shim that distributor to as close to 10thou as you can get it. Also, spin the gear with your hand while you have it out, give a good spin. I've seen them contact the "Star" on the top making a clicking sound

 

I meant fuel pump may be noisy ... I just wrote 0.015 to 0.020
Agreed ... The star is the reluctor ... the pickup coil can be loosened and adjusted

 

Excess wear in shaft bushings ... especially top bushing ... will cause too much shaft SIDE play ...
... too much Can allow reluctor to contact "teeth" of pickup coil.

 

Did you look under the hood in complete darkness to see if there may be an ignition spark jumping to ground somewhere?

 

Yes, i did but there was no ignition spark jumping .

 

I wonder if we’re dealing with a con rod or piston slap due to worn or broken skirt?

was there an event that preceded this noise? Or has this always been present since you acquired the car?

 

The tick was there all at once and the sound gradually got louder.