MTFCA Forum

Is this a knock?
Video link —> https://youtu.be/nd7Qv7II0OE

what else would you call it? Unless it is an exhaust leak (and it doesn't sound like it), I would certainly classify it as such.

a little history regarding how things were immediately BEFORE this sound cropped up might be useful if you are asking for advice

Possibly a piston hitting the head. Is this a new sound? Did you just do some engine work before this. Does it go away after the engine warms up?
Sometimes a new head has a little different area at the edge of the cylinder and if you can find the spot where it is hitting, grind just a little off that area of the head not damaging the area covered by the gasket.
Also another thing could be if the cylinders have been bored to a large oversize and the piston is a bit larger in diameter.
Other cause could be aluminum pistons a little loose, but they expand with heat and the knock goes away when it warms up.
Try driving it at slow speeds till the engine warms up and see if it goes away.
Anyway, if the head is off and the engine is cold with aluminum pistons you might be able to rock the piston back and forth at the top This can also indicate the block does need re-boring if the area toward the top of the cylinders is larger in circumference than the area below where the rings are at the bottom.
Sorry to give you so many possibilities to check.
Norm

A little history on the car to help. It had a distributor but I couldn’t get it to run right with it so I removed it and replaced with a timer from Lang’s. I bought rebuilt coils from midnight coil repair and new wiring harness. Put it all together a couple weeks ago and it drove great. I took it around the neighborhood and parked it. Today I started it and that’s what I heard. I didn’t hear that sound 2 weeks ago but only drove it one time for about 10 minutes.

What timer? Anderson timer flapper can bend a contact inside if you didnt set the retard to start. Pull the timer for a look. Just a thought.
Is this a fresh motor? Didnt forget to put oil in? Internal oil line left out? Shooting in the dark. Check timing & linkage.
Pan bolt under timer making contact with a terminal?(This bolt goes in backwards to the other pan bolts to clear the timer terminal)

An old trick is to use a screwdriver to short out each plug one at a time. That might give you a general idea which cylinder gets quite when it’s shorted out. I’d try that first before pulling the head. Sounds like a manifold leak but might not be.
If it started knocking after you removed the distributor that could be a clue. Maybe the camshaft front bearing? Something with the timer?

To me it sounds like a clumping sound more than a defined knock.

I did notice some smoke coming out of the manifold. Would that cause a sound like that?

There shouldn’t be ANY smoke coming out of the manifold where it is attached to the side of the block. If it’s chuffing there you need to remove both manifolds and replace the gland rings or the gaskets if that’s what’s used.
If it has flat gaskets it could be the manifold is slightly warped to where you can’t use the gland rings in each port. Flat gaskets are a fix if the manifold is slightly warped.

Knowing now that this developed out of "nowhere", along with More listening and more watching makes me wonder if perhaps the fan is hitting something. It is a very tinny sound, and the periodicity of the sound seems to be a single-cylinder event or a single fan-rotation event. I would be checking the lower hose connection/hose clamp for interference with the fan blade.

Throttling the engine down to an idle and using a stethoscope (carefully), will certainly isolate it, along with shorting out each plug momentarily and listening for differences in sound

Thanks all! Will be going through the suggestions tomorrow morning.

Each timer is different in the location of the retard for starting. The rod must be adjusted so the spark comes just after the piston reaches top dead center on the compression stroke. On most crankshafts the pin which holds the front pulley is straight across at top dead center. rotate the crankshaft to the pin at about 10 and 4 on a clock dial when viewed from the front of the car. Doesn't care which cylinder is ready to fire, so with the timer rod disconnected from the timer, turn the key to battery and then move with the hole for the rod near the top, set the timer so the spark to buzz just as you turn the timer counter clockwise. Then slowly turn the crank till it buzzes another coil. It should come at the same position of the crankshaft pin. Now adjust the rod to the length to fit with the timer at this same position and the spark rod all the way up.
With this position for starting the engine pull the lever about half way down to the point where it runs faster and smoother for fast idle. This is the position to drive at slower speeds. If you get around 30 mph you will find another position where the engine will speed up a bit on level ground. That is where you drive it at higher speeds. If it still knocks when adjusted this way, the knock is not in the timing.
Norm