Hello all, recently I picked up a bird for..a HELL of a deal!
91 ws6 bird, 5 speed, carb'd 305 with 993 heads, CP pistons, wrapped headers, Eddy rpm intake and holley 4150, unknown cam but sounds to have some lope mixed with pulling like a freight train till around 4500rpm..
Anyways, this thing has an odd knocking sound that I can't pin down for the life of me.
I have straight pipes, which does and doesn't help..

It doesn't sound like an engine knock.
Only heard at idle rpm, doesn't matter if I'm still or doing 60 in neutral, goes away once I get passed 1000rpm hot or cold.
Adjusted valves, everything in engine bay is snug..almost sounds like a pipe clanging somewhere.

Can't be heard from engine bay, I can only hear it through the exhaust. It's not a constant knock-knock-knock-knock more like. Knock.....knock.......knock.....knock knock....knock..but always in that pattern.
Just put new header and collecter gaskets on, that changed nothing. Premium gas..
Unplugging a cyl at a time does nothing, its still there.
The knock from inside the car makes the same noise as a rod knock.

Temp wise, I don't actually know, my gauge reads 220 on cold start, 300 later, and no oil gauge to speek of.. But new thermostat and has a 3 core rad with twin electric fans. I'm not burning anything though. Rpm does fluctuate at idle, it jumps roughly 40 rpm, otherwise runs like a champ.

No flat lobes or collapsed lifters..tried loosening em till they chatter on all 8, and then going a turn past zero lash as well, zero difference.

It's driving me nuts! ANY ideas on where to look?

 

Anyway you could put up a video of it? Might help some others to offer some insight.

 

You can use a mechanics stethoscope to try to narrow the spot down. It can be found at most auto parts stores.
You will be amazed at what you can hear with it.
= http://www.oreillyauto.com/site/c/de...0716&ppt=C0374

 

Way harder than it sounds lol. Potato quality camera, straight pipes and Kansas wind = couldn't hear much of anything

 

There's the other part, I borrowed one and listened around the motor, I can't hear anything out of the ordinary

 

Aha! Got a video .

 

Voltage at dizzy is a constant 13.6v, no fluctuations. Bottom end sounds fine, dizzy cap and rotor are good, no wires crossed..I do have an exhaust leak at my collectors, a pretty decent one. Only thing I can think of at this point is exhaust leak mixed with exhaust exiting in front of front wheel mixed with a lopey cam = exhaust popping that sounds like a knock.