help tracking down knocking...
 

As far as I know, the engine is the stock 352 in my '65 F250, although headers have been added by a previous owner.

There is a faint knocking sound while revving it in neutral, but gets a lot more noticeable while driving at higher RPMs. I'm thinking rod knock, but it almost sounds more like rapid tapping on a block of wood more so than metallic.

I haven't yet installed a tach, so I can't say for sure, but it occurs at the upper end of the RPM range before I shift (it's almost like an audible shift indicator, lol). If I'm cruising in 4th gear (4 spd manual, with granny first), at around 40-45, holding a steady RPM, it's obvious. But I found if I let off the gas ever so slightly, or give it bit more, again ever so slightly, it nearly disappears until the RPMs level out again. I've noticed the same behavior on the freeway at 60-65. But under that RPM, it seems fine, and I have enough where it's driveable without inducing the knock.

The knocking is tied to RPM, not road speed, and seems to happen at around the same RPM, and same intensity, regardless of what gear I'm in.

I tried pulling one plug wire at a time, and that didn't change the noise, although I did notice that the truck wouldn't start after I pulled one certain plug, but I didn't note which one it was (was shutting it down, pulling a wire, restarting and driving down the street a few hundred yards, then shutting down and pulling the next one). It started back up when I put that wire back on.

I've recently replaced the plugs, wires, cap, rotor, points, condensor about two weeks ago. Points at set at .016, I think I set the plugs at .030, timing is at 10 degrees BTDC. I did notice the timing jumping a bit when I was setting it, thinking it's time for a timing set. But if I have serious internal issues, I'm hesitant to put more money into this engine. I also just put on a new set of header to head gaskets (the Hooker 10825 that fit the ports properly), as well as a new set of collector gaskets on tonight, which also didn't change anything.

I also noticed that if I let the truck sit and idle for a few minutes, it starts popping out the exhaust, but it's making more of a "pooft" sound than what most people would consider a backfire (knowing many people call fuel burning in the exhaust a backfire..I know that a pop through the carb is an actual backfire, and I did get one of those while I was setting timing too).

I've tried backing the timing down to 3 degrees, and running 91 octane to rule out the ignition timing, and that didn't seem to make a difference, although starting it was a real PITA at 3 degrees timing, and there was a noticable power drop at 3. At 10, I've got gobs of power, enough so that the truck is capable of roasting the tires if I let it idle in 2nd gear, and floor the gas.

If the timing chain jumped a tooth, could it cause the knocking like this? Although I would think that if that were the case, I wouldn't have nearly the power that I do. I'm also wondering if maybe the springs in the distributor have gone weak, allowing too much timing to come in too early?

Don't take offense, but could you have swapped two plug wires? I"ve done that the odd time, and the engine can act similiar to what you're describing.

All I can think of at the moment. Not much, but free and easy to check.

Hope you get it figured out "cheaply".

ps: one other thought....check exhaust gaskets for leaks (look for soot, feel for hot air, etc.)

i have heard a similar noise on one of my motors turns out certain valve covers cant be used on other motors i had a set off of my 352 on my 390 and it had same noise you seem to be describing and it was my litter tapping the valve cover swapped back the stockers problem solved try pulling covers and see if it continues

Since you have a manual tranny, do this:

As you get to the RPM where you would notice this knock, apply pressure to the clutch.

The noise you describe might be crankshaft end-play. Pushing on the clutch will keep the crank from slapping back and forth (lengthwise).

The other thing that it might be is the eccentric for the fuel pump. Or if the spring in the fuel pump is getting weak, the level might be floating off the eccentric.

WELCOME to FTE! This is a great idea, could very well be exactly that.

Checked the firing order this morning, it's correct. I wasn't able to check anything else, as it didn't want to start. I'm thinking I just have a bad connection somewhere, as it's cranking fine, but doesn't sound like the ignition is firing at all....i'll dig into it when I get home from work tonight. Perhaps this will be the impetus I needed to do the DFI upgrade :D

Drain off some oil. Is there any metal shavings or sparkles in it?

Actually, forgot to mention that I did an oil change at the same time as the tune up stuff....I didn't notice anything obvious then, but then the oil was as black as night. I'm pretty sure I still have the oil in the drain pan, I'll check that tonight when I get home as well.

Any update as yet?