Yeah DHV I'm having similar problems. It makes a ticking sound at idle and this morning when I cranked the truck up it sounded like somebody threw a quarter into the intake manifold.

 

I'm having the same problem too in my 360, this past weekend on the way back from the scrap yard I was getting spark knock inspite of installing double platinum plugs, 180 degree t-stat, and replacing the plenum gasket last year to help eliminate it. Shortly after, while climbing a hill at about 3000rpm the check engine light started flashing, and a few miles later at around 2000rpm it started misfiring and shaking and feelig like the whole truck was gonna come apart, so I let off the throttle then eased back into it and all seemed fine. Then this morning I
started it up to go to town and it was ticking, not
positive but sounded like a valve, but it got a lot quieter once the engine warmed up. After reading several forums I'm almost positive a clogged cat caused the spark knock and possibly the misfire, but I'm wondering if I may have already damaged a valve?

 

Dump the platinum plugs. These trucks do not play well with them.

 

I think I just found the source of my ticking, I rerouted my spark plug wires in hopes to get rid of the spark knock and misfires and apparently accidently unplugged some vacuum hoses, which I think was the noise I wAs hearing. My inspection runs out tomorrow and I'm not re-inspecting it until May because I am moving to a different state so I won't be driving the truck much til then to confirm.

 

Again #5 cylinder is misfiring...all of a sudden this morning since I shut down engine last night. BTW, it was running just fine last night.
This happen about two years ago and it turned out to be an injector.
I checked for corrosion inside of the injector connector plug and injector resistance of 12 ohms. I heard clicking noise inside injector with a very quick 12 vdc contact to terminals. Applying voltage for a longer period of time will destroy the injector!!!! They are not designed to be of continuous duty.
Engine now running.
I checked for spark to plug (ok) and plug as well, replace plug and still has miss. I then checked continuity of wiring to #5 injector, voltage on DMM was a quick spike (pulse) on the DMM display from Cpu.
I changed out the injector and still had the same problem.
I'm really angry at this point, probably wasted money.
I took a chance and bought another injector (spare parts ok).
Replaced injector the second time and voila, runs great since.
Yes, although it may be very rare that a new injector is defective, it can happen.
Sure am happy it was not a valve/head problem.

 

hmm good read I'm having similiar issues with my #1 cylinder plug looks white on one side and unven burn... but I have noise that sound like air pressure escaping and noisy valves too.... only get the engine light and popping under load but missing all the time and shaking in overdrive because of it... damn cold weather... It driving me nuts not knowing.

 

Since my memory is bad and I read too many threads,and I don't know what all diagnostic procedures you have done to this point besides the basics. I'd say you simply have cracked heads.

 

Oops,

BTW, If one is not proficient in electronics/mechanical applications, please do not perform the below procedure. Damage to the PCM could occur.
PCM ground and Chassis grounds are two different points electronically.

The DVM setting should be in AC volts and not DC volts.
There are three connectors on the PCM. The one nearest the engine is plug number 1, the one in the middle is plug number 2 and the last plug nearest the fender is number 3.
Be very careful when searching for various wires within the harnesses...especially the color coded ones.
The wires coming out of connector "2" at the PCM, Grey wire (#5 injector) and connector "1" at PCM, Black/Lt Blue (PCM ground, NOT CHASSIS GROUND!) are the reference points.
After locating these wires, carefully remove a small amount of insulation to expose conductors being careful not to cut into the wires.
Connect meter Black probe wire to Blk/Lt Blu wire and meter Red probe to Gry wire.
Select the low scale/auto range AC volts on DVM.
With engine running, the reading on the display should pulse showing about 1.4 to 1.1 Vac.
This is an excellent means to show the DC voltage (pulses) is being "pulled down" via the device within the PCM without the use of a scope.
I hope my test procedures are helpful to those that enjoy troubleshooting.

 

yeah it seems that way... besides the usual cap rotor wires and plugs I just checked tightness of headers for leaks and tried a bit of mmo on the valves / oil and seafoamed it... I have to do a compression test but my garage is an overpacked mess right now...I havent been driving the truck much at all... I recently replaced an 02 sensor and cat right before this became an issue.
it almost sounds like I could have a bad gasket because I hear a pulsing air noise I cant trace from the #1 area but vacum seems fine..I have to try oil or seafoam to get it to smoke again in the daytime and look for leaks..the head seems noisy so maybe I have a broken valve spring. The half burned plug seems to point to a cracked head though I agree.. its so rusty I need to wait for better weather to tear into it. oh yeah 300 and 301 misfire codes...they took a while to come up and it pops under load when the codes usually come up.

thanks liarbear.. I may try that or even swapping two injectors to see if the mis moves... I did practically run the trck out of gas before all this so maybe I have a half fouled injector? wishfull thinking I know...

 

I assume you've also replaced the crank and cam sensors to no avail?