Top end knock

[Skyview69]

Hello,

My 69 383 has developed a loud knock. Sounds like coming from The top end. I pulled the pass side valve cover (that's where I think the sound was coming from) and tired a spare rocker arm and rockers I had, inspected the rods. Did not work. Any ideas on what to check out next?  It has good oil pressure.

Thanks

[c00nhunterjoe]

Pull a plug wire 1 at a time and try to isolate.

[Skyview69]

Pull a plug wire 1 at a time and try to isolate.

What exactly does that do? Are you saying the knock will go away when that cylinder is not firing?

[c00nhunterjoe]

Depending on what is causing the knock, the lack of load from the power stroke will dull or eliminate the knock on the offending cylinder helping to isolate it.

[Skyview69]

Worth a try...thanks

[Challenger340]

There is only so much in the top end, that as you describe can "knock" ?  and usually "top end" noises are more "tics" than knocks ?
Enough of the lingo stuff....
as mentioned, pull the plug wires one by one when running, and see if you can "change" the knock/tic/noise to a particular Cylinder.

[Kern Dog]

I had a slant six in a Dart that had one bad rod bearing. It sounded like a washing machine with a size 13 work boot in there.  With it running, I'd pull the plug wire off that went to that cylinder and it barely made any noise. When I pulled the engine to swap in another, I pulled the pan to get a look. The rod bearing was totally gone and the rod just rattled on the crank. Knowing the durability of the slant six, it may have lasted a few more days before putting a window in the block.

Now, regarding a top end noise, know this: Several things car make noise and rarely do they just go away on their own. Top end/valvetrain noises are usually higher pitch as compared to the deeper bass type thunk noises you'll get from a rod or main bearing going bad.

If this is a "sudden" problem that never existed before, what sort of driving were you doing before it happened? High RPMs? Extended low rpm cruising? A long period of inactivity?

Regardless, you should at least pull the valve covers to get a look at every rocker arm. In some cases of high mileage, the end of a pushrod can wear through the rocker arm and punch through. Aside from some tapping noise, this will also result in the engine running rougher than usual since the affected rocker arm will not be operating at its full range. If all of the rocker arms seem okay, take a look at the pushrods. If any are bent, this will result in excessive clearance between the pushrod and rocker arm, leading to a tapping noise.  Look at the 5 attaching bolts retaining each rocker shaft. If any are loose or missing, the shaft will flex when the engine is running, leading to increased pushrod to rocker arm clearance.

In 2006 I was on the way back from the 7-11 with a Big Gulp. The Charger started to run rough and the oil pressure dropped off. At home I pulled the valve covers and saw that the rocker shaft on 1 side had broken into 3 pieces! I pulled the intake and saw that there were 4 pushrods sitting in the lifter valley and 4 lifters had popped up out of their holes!  The rocker shafts came from a police 440 that I had rebuilt awhile back. That engine puked a rod at 846 miles! I think that engine was cursed.

Now...If the problem is NOT valvetrain related, I'd have to go back to the underground lab and think on it some more.

[Skyview69]

Thanks for the tips. I will try the plug wires next weekend

[Skyview69]

Tried pulling the plugs one at a time.   Still making the noise. Any other idea's

[BSB67]

Give as much detail on the specifics as possible.

[c00nhunterjoe]

Try taking a quality video of it and upload it to youtube

[RECHRGD]

A leaky manifold/header gasket can make a heck of a racket........