Engine Noise/Tick at Higher RPM

[52b3b Joe]

I've been having a strange engine sound randomly at higher cruising speeds 60-65 mph (keep in mind I have a 3.54 rear end), and I've been trying to locate the issue. The noise it a loud tick that will last for a few seconds, then go away. Loud enough to make my wife nervous (you can EASILY hear it over the wind noise, glasspack exhaust, and radio). It is with engine speed but doesn't hit every revolution if that makes sense? It is not a regular occurance, and is extreamly random. I can drive the truck for hours without having the noise, then one day it happens 3 times in 5 miles. I only notice it at higher RPMs.  I thought I figured it out earlier this summer with a broken pressure plate finger pivot. I had the pressure plate rebuilt, and put a new disc and pilot bushing in, but I still have the noise (but a better feeling clutch with no chatter!). Nothing is hitting or making contact in the clutch area that I can see. 

 

My next thought was to remove the engine oil pan to fix and oil leak and look for any foregin objects in the pan. I though maybe something was loose in the pan. The pan was very clean and the lower end of the engine looks fine. The pan has had a rough past, with a lot of dents/dings. There is a spot near the #5 rod where it looks like something has rubbed the pan and put a shinny small grove in it, but no sign on the rod or rod stud/nut of hitting. I suppose it's possible with a softer material for the pan. This might be the noise, but I don't know how it could only happen at higher RMP, and you'd think after 4,200 miles on the engine, it wouldn't be a recent issue. There was also NO metal glitter in the pan. I ran a magnet through every square inch, and picked up nothing. I guess I'll just cleanence the pan where the mark is, and reinstall it. 

 

The only other thing that is questionable is the fuel pump arm spring pressure on the cam. When it is not on the high part of the lobe, there is not much pressure keeping the arm on the cam. I am wondering if it is "floating" the arm on the cam lobe causing the noise. How much tension is normally on the cam when the pump is off the high point on the lobe? I can eaily pull it back with one finger about an 1/8". 

 

Beyond that, I have a leaky exhaust manifold (I hope it's not cracked) that I'm pulling off tonight, and plan to pull the valve covers to see if anything in there might be making the noise. 

 

Has anyone else had a similar problem? I'm guessing not, but you never know! 

 

Once I get these small issues corrected, we'll keep on truckin! 

[Don Coatney]

You might want to get a mechanics stethoscope to try and pin the noise down. 4 bucks at harbor freight.

 

https://www.harborfreight.com/mechanics-stethoscope-63691.html

 

[52b3b Joe]

16 minutes ago, Don Coatney said:

You might want to get a mechanics stethoscope to try and pin the noise down. 4 bucks at harbor freight.

 

https://www.harborfreight.com/mechanics-stethoscope-63691.html

 

 

I have one, but I can't get it to do it on command, and it doesn't make the noise for a long enough duration to go this route I think. If it still makes the noise after I get it back together, I'll give it a shot though. 

[JBNeal]

Put some Marvel Mystery Oil in the crankcase and see if that helps...ya might have a sticky valve

[52b3b Joe]

2 minutes ago, JBNeal said:

Put some Marvel Mystery Oil in the crankcase and see if that helps...ya might have a sticky valve

 

That's actually makes the most sense. The noise isn't 100% metalic, and sometimes sounds like the mix between a miss and an exhaust leak, which is pretty much exactly what I'd have with a valve problem. What I don't get is the fact that I drive the truck quite a bit for a valve to do that, but who knows? Maybe I should pull the head too and take a look at them. 

[JBNeal]

If there is some gum on that valve, it will ball up on the valve stem, hanging the valve until it vibrates loose and flattens the gum higher or lower on the valve stem, repeating the process...check your valve galley to see any evidence there...ya might be able to narrow down which cylinder is affected, then squirt some MMO on the faulty valve and let it sit overnight to try to wash off the gummy stem...but definitely put MMO in the crankcase oil to circulate in the system and clear out any gum near the valve areas

[Jerry Roberts]

Put a little MMO in the gas too . 

[ggdad1951]

I say scarp the whole thing and send me the grill bars for safekeeping...or unstick the likely culprit (valve)

[NiftyFifty]

If the MMO doesn't fix it, check your u-joints...I had one on my 67 Monaco that would occasionally "tick" at higher speed and it was a case of it just starting to seize up a bit, and possibly the little bit of extra torque at higher rpm changed the pitch just enough for it to make noise...I hunted that one for awhile too, but I'd agree it's most likely a valve and MMO solves most problems.  Definitely run it in your fuel tank as well.

[52b3b Joe]

I'll definitly start to use MMO. My dad has used it religously in his 41 Desoto, but I always thought it was a waste of money. Maybe not! I am thinking that my engine might have a little tighter tolerences than spec on the valves, and that is the main factor, but I'm just guessing. 

 

I checked the u-joints when I had the driveshaft out earlier this year, and all seemed well. I also replaced the u-joints when I restored the truck too. 

[HotRodTractor]

Years ago I had a '53 Pilothouse that had a random tick. I had no history on the engine other than it was a Plymouth 218. One day I was in an auto parts store and saw some "Prolong" sitting on a shelf and I remember some late night infomercial about them running engines without oil for hours after being treated. I figure - its only a few buck so I buy it. I dumped that bottle into the crankcase with the engine running...... I have never heard a more drastic improvement on how smooth an engine runs than I did in the few seconds after I dumped that bottle in.... it made me a believer that its more than snake oil.

[lonejacklarry]

Prolong products are still around.  I've never used them so I cannot offer an opinion of their effectiveness.

[Ram Man 02]

i have nothing useful to add but do want to say that it never gets old seeing pictures of your beautiful truck!

[classiccarjack]

Please let us know if the MMO worked...

[52b3b Joe]

I took the weekend off from the garage. As the truck sits, the pan is back on, and the manifolds are off to the machine shop to get trued up. I plan on pulling the valve covers tonight to see if I notice any signs of a sticky valve based on what Brian said to look for. It'll actually be easy to see what I'm doing with the manifolds off! I'll let you know what I find! 

[johnsartain]

If you are using the stock starter for the L6 engine, it may be the bendix contacting the flywheel. Put a spring on the actuator lever to hold it out of the way and see if it stops.

[52b3b Joe]

1 hour ago, johnsartain said:

If you are using the stock starter for the L6 engine, it may be the bendix contacting the flywheel. Put a spring on the actuator lever to hold it out of the way and see if it stops.

 

I actually had the same thought about the noise, but I don't see any indications on the ring gear of contact, and the return spring on my starter is pretty darn stiff! Have you had this problem on one? I might check it out again though for ease of mind. 

[johnsartain]

Yes I did, I would drive down the road and hear a random tick. I couldn't figure it out. I noticed that I could hear it sitting still when I revved the engine. Never was rhythmic like a tappet.  Just  a tick... tick, tick ..., ... tick. I had my son rev the engine and I could see the actuator lever move back and forth with the tick. I put the spring on and not more tick. Like you there was not marking on the bendix or flywheel gear. It wasn't hitting that hard.

[Merle Coggins]

Interesting... It would be an easy enough test. Put a spring, or bungee, on the starter arm to ensure it’s staying up and go for a drive.