OK, this continues to drive me crazy, need your ears, it won't be easy

[jayb]

Ross, what oil pan do you have on that truck?  Its not that Canton pan, is it?

[My427stang]

Not talking about initial setting, but the rate of advance just off idle.  Seems too fast to my ears.  I have experienced that with FEs and stroker sbfs.  Slow down the rate off idle.  Since the oil pump is driven by the distributor gear and shaft, you may be fighting yourself for an instant with the oil pressure.  Just an observation.  Joe-JDC

Joe, I understood you, and it was a good idea, but I would think a change of 10 degrees initial would overcome too quick of curve. Heck I even cranked it back far enough it backfired on me on one run. It basically makes it 10 degrees less everywhere on the curve.  That being said, I will map out the curve and put it on paper.  It's not a very fast curve, it's a 4500 lb 4x4 truck and the noise is pretty rhythmic, unlike a quick onset ping, the odd thing is it seems slow for a piston noise, but I suppose it could be half speed with the cylinder only firing every other stroke. 

I appreciate the ideas, and please keep them coming, even if i have already looked at them, like I said, if it was normal stuff it would have been fixed over a year ago.  My hunch is still on a bad piston that I somehow missed, but I am getting sick of pulling this engine!

Ross, what oil pan do you have on that truck?  Its not that Canton pan, is it?

Stock Ford 4x4 rear sump, aftermarket pickup and Ford windage tray.  The pickup lives entirely below the windage tray, and  I have ran it with and without the windage tray and headers have clearance to the pan.

[gregb]

Would pulling one plug wire at a time and driving it at least help isolate which cylinder?  Or would the resulting misfire be too noisy and cover up the rattle?

[Drew Pojedinec]

Would pulling one plug wire at a time and driving it at least help isolate which cylinder?  Or would the resulting misfire be too noisy and cover up the rattle?

I'd suspect you'd never hear the tick sound over the resulting knock.
You could find it this way maybe on a dyno, but I think it'd be real hard to hear/see it in the truck while it's moving.

[jayb]

I'm not sure that you wouldn't be able to hear it.  In fact, I'll bet you would still be able to hear it if you are tuned into that particular noise.  What about it, Ross, worth a try?

[plovett]

I'm not much help.  I can't definitively hear anything either.

So the sound is rpm related and not speed related? And mostly under load?  And louder when cold?

Those are the main clues I think you have?  Does that fit your piston hypothesis?  What exact piston issue do you think you might have?

Only other thought I had is can you quiet the exhaust down?  Clamp some big-ass mufflers on to your tailpipes, or otherwise muffle it horribly?

paulie

[chris401]

Would pulling one plug wire at a time and driving it at least help isolate which cylinder?  Or would the resulting misfire be too noisy and cover up the rattle?

Yes that is a real test. It is a common practice in many scenarios. The noise a loose or cracked piston makes is unique. Once I had a noise on my own truck where I went through the same testing. Turns out my flywheel was lightly hammering idle-off idle due to the .009" end play.

Ross if you want to try a quicker thing thrust your crank back and fourth by hand and listen if you hear the same noise.

[Barry_R]

Sounds like you answered my best guess - windage trays can make some amazing noises.  That flat expanse of tin amplifies a small touch into one heck of a racket.

[My427stang]

Well my piston thought is potentially a crack, certainly not loose, not to mention when I reblocked, blaming it on piston slap because I originally built it loose, the noise didn't change with a tighter bore.  I have measured bore clearance twice now and they are exactly where the manufacturer wanted them and straight as an arrow.  FWIW they are Probe forged pistons, not the best out there, but the price was right and this was going to be a relatively low RPM stroker

However, if a piston was cracked, you'd think something would have let go by now, or at least you'd think it'd leave a mark, it's seen 6000+ plenty of times and more miles than you'd expect, also no funky wear on the bores or pistons

Crank thrust measured good and is on the tight side, I looked as well to see if anything could hit and even had two sets of bearings in it.

Paulie, your summary is correct.  Idles quiet, wing the throttle quiet, back out of the garage, accelerate away, almost sounds like a Chebby with a loose rocker, very loud cold, and can almost sound squeaky at first, as it warms up, truck doesn't get too warm, only has a 160 degree thermostat, but it gets much quieter.  Almost to the point that you can ignore it, but it's still there during acceleration.  I had thought stuck or dry wrist pin, but I had them all out this time when I checked all the pins and small ends and nothing goofy.  Exhaust is pretty quiet in the cab, not sure how I could make it much quieter.  I hear the noise, I can point to it as potentially right rear of the engine while driving, but can't duplicate it under the hood and can't find anything loose or worn and as much as I am a brave man, I cannot sit in the engine compartment and drive around    I even had a Bluetooth listening device with 8 channels clipped all over the engine under the hood and all that did was alert me to how freaking noisy a solid lifter engine was when magnified by a bunch of electronic sensors! LOL

A stumper for sure.   I will try pulling a plug wire at a time and see if it goes away.  It seems to be on the passenger side, so it won't take too many tries LOL

Hell even if I could only isolate a hole, that would be the biggest gain in this whole endeavor so far

[plovett]

I once had a rocker arm adjuster jut barely hitting the sheet metal baffle under my Mercury Pentroof valve covers.  I have Harland Sharp rocker arms with Dove stands and end stands.  I had rounded off the hex wrench hole on some of my rocker arm adjusters and bought some new Harland Sharp adjusters.  The new adjusters are better.  They have a larger hex wrench hole in the top, AND they're longer.  Long enough that by chance, when I installed one of the new adjusters, it was under the baffle in my valve cover, and it hit, when the old adjusters did not.  It smashed up the baffle and made some noise.  I ended up just swapping it with the adjuster on another rocker arm that was the old, short, style. 

I'm reaching.  But who knows?

paulie

[My427stang]

Multiple rockers and valve covers to include stock rockers with a 270H at the beginning. Currently no baffle chrome Pentroods on it  Confident it isn't that, but keep them coming

I was really leaning that way for a while, even had Brent put an eye on all the retainers and springs and had the heads magnafluxed reaching for a broken valve guide boss or seat bouncing around.  Nothing....

This weekend, I am going to try pulling a plug wire and driving to see what changes, feeling better that it is piston related, but not good enough yet to tear it down again

In fact, unless I somehow magically find something definitive, it is likely going to get a stout little 396 for a while, I need a break

[cjshaker]

You know that old Sherlock quote..."when you have eliminated the impossible, whatever remains, however improbable, must be the truth"
I still wouldn't discount the idea that it may not even be engine related, but it's hard to say since I cant hear it. I just know I've been fooled more than once that way.

[Tobbemek]

This weekend, I am going to try pulling a plug wire and driving to see what changes, feeling better that it is piston related, but not good enough yet to tear it down again

  Good decision ,just be shore the spark, if it is a MSD ignition, has som way to get out of the system
ore you an get nasty sparking going on inside the MSD box and ruin it, i know dun that when they was new on the market here in the 80is .
My first impression was a piston/combustion  related noise,  how is your sparkplug wiring, are they nicely separated or in bundles.

Back in the 60is i think it was, there was a memo from FOMOCO how to cross nr: 7and8 plug wire ( even nicely separated in holders) to eliminate induction premature firing the nr:8 cylinder Especially 7and 8 plug wire shroud not run along side each other with out crossing  twice.
and how you should arrange plug wires ( 7,8 ) at the dist- cap .the longer  distance and the closer they are along side, the greater the induction spark.   Think good people here has most possibility's covered 


 

[country63sedan]

Let me start by saying that I can't hear it - maybe you should stop by Mack and give me a ride.  I do have a quick and easy guess at it though. How about the speedo cable? It should be easy enough to take it loose down below and go around the block.  Later, Travis.

[My427stang]

It's clearly an engine noise, hard to hear in the video, but it's clear as day in the truck. Especially cold

I was going to troubleshoot today, but decided to take the Mustang out and having too much fun