The Stovebolt Site Forums The Shop Area Engine Shop 235 six with "tapping, pinging" noise?

Hi guys,

My truck has been running excellent for the past year since I got it running...until last night, it started to make a pinging, or tapping, noise while driving. It progressively got louder and louder until I got it home, now it's parked until I can find the time to tinker with it to see what the issue is.
It shows up very audibly if I put the truck under load, like going up a hill. Just idling, I don't hear it at all, even if I rev it. Definitely not a low end clunk, so I don't think its a bearing...it's a tapping, sounds like something small...definitely a metallic sound. My best guess is a stuck lifter, or my rocker arms need adjustment, but I don't really know, as I am still new to the hobby. Seeing how it's not a daily driver, I don't mind having to take apart the engine until I find what it is, but, was wondering if anyone had suggestions as to what to look out for when i take apart the engine.

The truck is a 61 by the way, with its original 235.

Thanks!

one thing to check (and not the only)
is for a bent push rod
...pic...

that would make more of a tapping noise

Valve train noises usually don't change with changes in engine load.
If it is quieter when the oil is cold suspect rod bearing problems--and there is, when warmed up, usually a speed where it will be a chatter or rattle.This may be up around 1500-2000 RPM unloaded.
At idle shorting out 1 plug after another may show a change in noise when the guilty cylinder is found.
An exhaust leak where the manifold joins the head will give an almost tapping sound that will go away when you let up on the gas.It will probably be worse cold than hot because the gap usually closes up as the hot manifold grows.
Again, valve noises usually don't change as the load changes.

Ok...say that the problem is the connecting rod bearings. those can be changed without having to overhaul the block, right? Pull the pan off, take off the end caps, tap the upper bearing halves out, tap in new ones?

...unless of course the crank or the block are scored.

my truck sounded similar, but it turned out to be a leaky exhaust gasket where the manifold and pipe meet. (thats 2 with the same suggestion) I would go there long before I started tearing into the engine. I would do a lot of studying and get one of those mechanic stethascope things and do some listening around before I came to any hasty conclusions that involve tearing the engine down. But if you have an original 61 engine, there is a good possibility it needs rebuilt anyway.

I would think rod bearing noises are a thunk sound that you'd be able to recognize as the sound is deeper within the block.
A tapping sound to me, points to slack in rocker arm activity (lack of oil, excessive slack).
If exhaust, your ear should locate the sound to that side of the engine... if lifter/push rod, to the top.
If it were me, I'd first pull the valve cover and investigtate the action... and go from there.
Jerry

Thanks for the advice guys. I think I will start with checking out the guts under the valve cover and inspecting the exhaust. Now if it would only warm up so I could work on it! -28 degrees celsius here in Calgary today! The truck is in a garage but there's no heat!

An easy and cheap way to determine where noises are coming from in an engine is to use a 1/2 inch long extension. Put one end to the engine and cup the other with your hand to your ear. You'd be surprised at what you can hear.

As rickmg says, you can isolate an area of noise quite easily just by listening to various points around the engine. My favorite listening stick is a long screwdriver, handle to my ear, works great.
Manifold gaskets can be difficult to seal on these motors. I've found intake leaks by spraying Berrymans Chemtool around manifold with engine running, if she speeds up you've lost your intake seal.

Best of luck.

Sounds like what we used to call "spark knock" (detonation). Where did you fill up last? Could be bad gas but I'd also check your point gap and timing. If it only shows up under a load this sounds like it could be the culprit. Also check your vacuum advance unit to see that it's operating freely and not sticking.

That was my first thought, spark knock.

Detonation...yeah I never thought of that! I filled it up at a Safeway gas station last, but I've taken it there before. I reset the timing about a year ago, but I've never checked the points in as long as I've had the truck. I don't know anything about points...what should I be checking for? What do I do? And the vacuum advance, that's in the distributor isn't it? The whole distributor moves when the engine is revved.

Yeah that noise shows up only under load, not when idling or revved.

Have a look at the shop manual, under "Tune-up" or something like that.

If the distributor moves back and forth you're good to go on that one. Check to see if the distributor locking bolt is tight, it should only go so far and then right back. To check the points, pop the cap off the distributor, and turn the engine over by hand until the rubbing block pushes the points open to the widest point. Points should be nice and clean, no pitting, corrosion, or other nasties. A .016" feeler should fit in the gap. If not, loosen the lock screw and adjust them so it does. After that, recheck the timing.

Thanks Waldo, sounds easy as pie. I have the shop manual too, somewhere. Will have to find it and do some reading.

FYI - I had a brassy sound and or knocking a bit, nothing like a bad rod , while under load or crusing around 50. I redid the timing, adjusted the valves about 4 times to be certain( in case slop in rockers as ealier comment and added Lucus oil addative , heavy oil 50% and the noise is gone. I don't know!! Just my 2 cents.

Ok, so I finally tackled the truck tonight because it has warmed up. I redid the timing, it was barely out, that didn't solve the pinging. What I did find however was a bent pushrod. Do you guys think that could be it? I'm gonna replace the rods anyway, it's too bent to keep driving it. And also, what causes a rod to bend like that? Should I replace the lifters too, or is that not necessary?

My bent rod sounded like THIS

It bent after the tuuck sat for a while. Valve stuck

I only replaced the bad rod and reset lash.
Someone else may advise on weather you should replace lifter or not. I did not

Good Luck

Mine sounds normal when idling. Doesn't sound anything like that, but, my bent rod was doing the circle dance like yours was.:D I've been driving it for over a year and it only started doing this a week ago. My truck has sat for a very long time though, prior to me driving it. It's had about 3000 miles or so put on it since 1987, so it was used very little since. The valve springs and rocker arms are all moving as they should though, so I dont think one of my valves is stuck...at least I hope not.

Excellent way of describing and engine noise Gus a big thumbs up to ya.
All to often we here people try to describe a noise by the written word and we all have
different interpretations of what it might sound like. It’s like trying to describe a color or
smell. One of our members was asking about a loose heat riser valve yesterday. How
loose is loose and how would you describe the problem?
Some years ago I brought up the idea that someone looking for a project should make
an audio/video of engine sounds. I think a CD would really sell if it was well done.
Take a good engine and maladjusted the valves or replace a good piston or rod or main
bearing with a bad one to show what these sounded like. A rod knock or piston slap or
loose wrist pin or clunking main bearings are hard to describe to most people but a good
audio of them would really clear the air. A good example is the previously mentioned
loose heat riser, if its just a little puffing from the shaft then its no problem and an
audio/video of that would say it with one look & listen.

Thanks Gus, I wish I knew how to manipulate those videos, I’d be using them in my
replies for sure.

Denny Graham
Sandwich, IL

Denny, I like the audio/video idea of engine sounds. Brings back memories of my first father in law. Old guy raised the the mountains of NC, no education, worked on cars all his life untill the age of electonics. He just didn't know how to do it. He could dignose a problem just by listening to the sound. He worked for a small Chrysler dealer in Louisa Va and the owner had a collection of old cars to rival the best of collections. Mr Pettit, WAC Pettit III, had everything from 1928 Rolls to the plain old Plymounth sedans. That old man could work on all of them with confidence and all through the sound. I miss that old man.Larry

Thanks for your comments Denny.Im a noob at all this, so the videos help me quite a bit.
Picasa, Flickr, and photo bucket allow uploading of videos, and are free.
BigTonka schooled me on loading videos to picasa


Adam61
let us know if it improves after you replace the rod. I picked up rods for my 235 at NAPA.
Here is how it sounded after I replaced the rod. ..click...

You still may have other issues described earlier in the thread.

Gus -

Thanks for posting the videos and before-and-after sounds.

> I see that you cut out the top of a valve cover to contain the oil while checking and adjusting your valves. How much splash and dribble do you think that it will make in my engine bay if I don't use a similar baffle when adjusting and checking the movement of my valves? I'm reluctant to chop off the top of my spare valve cover for what will probably be a one-time job. FYI - I will clean the engine afterwards to prep for painting the engine.

> Also - did you torque the head before adjusting the valves, as directed in the Shop Manual? The head and gasket are good on my truck. Not looking to cause a problem if none exists.

It's probably evident that I've never adjusted solid lifter valves before. And only played with hydrolic lifter valves once - and that was on a 327 in 1965.

I purchased a used cover at a swap meet for a few bucks, that’s why I had no problem cutting it up.
There is not much oil dripping off the rockers at idle, you may only have to dam the rear near the firewall if you choose not to use an open cover.

A while back I found a small coolant leak dripping off the head near the firewall.
I posted a question in the forum and It was suggested by Pre '68 Dave to try re-torqueing the head bolts.
I did the re-torque and the leak stopped.
Then I re-adjusted valves the after the re-torque, again suggested by Pre '68 Dave

Lonnie, I adjust my valves while with the engine running all the
time, as Gus says, there is just a dribble out of the rockers
at idle. I don't really have much trouble with getting oil down
the side of the head.
Only problem you'll have retorqing the
head will be that dang center head bolt.

Denny G

Thanks for the info, guys.

Hope to try my hand at adjusting valves in the next couple of weeks ... after water pump and motor mounts.

Do any of you know if other Chevy inline six engines, or even the V8 engines, use the same pushrods as a 235? Napa can't get them for me...I'm gonna try a few other places, but was wondering in case I have to get them from a wrecking yard.

Napa should have been able to get them. The part number is SEP RP3020.

I called Napa today, they said they have a part listing but nowhere to order them from because it seems nobody has them. He's gonna take it to management and give me a call tomorrow. And we don't have Orielly in Canada.

try Rock Auto online also

They list the RP number referenced by LONGBOX55

deleted my earlier post

Well, I finally got the new pushrods, and I installed them today, replacing the bent one and all the rest. I put it all back together and took it for a spin down the street. No difference. I still have the pinging noise. I also have noticed that while cranking the engine to start it, I hear almost what sounds like air being blown through a small opening somewhere, like it's in one of the cylinders or something. I can hear this same sound when taking off from a stop. Standing by the exhaust pipe while the engine is running, I've noticed that it now has a miss. It used to idle with a really steady hum, now it chugs sorta. My best guess is I have a burned out valve. I really hope I'm not right. Anyone else have anything to throw at this?

Same symptoms a few months ago had too replace push rod guides was not done when engine was over hauled, their mistake or oversight.

Go back and check your valves one more time. You may have missed one. It wouldn't be the first time thats happened.Larry

What do you mean "check the valves"? I haven't adjusted the valve lash yet...think that might be it? That air blowing noise and the miss in the idle is pretty obvious, and it didn't do that at all before. Maybe one valve is set too tight and never really closing? I'm learning still, kinda flying by the seat of my pants, ha ha

Sounds like the cart getting ahead of the horse. Why would you take it for a drive and not check and adjust the valves first? Repairing anything from a old truck to putting together kids toys you have to start with #1 and then follow the steps. If you work through everything needed to make a truck run you will know what to expect when you get to running and driving it. You need to make sure you have good spark, good fuel supply, good compression. Turn your engine over by hand and watch to make sure you don't have a valve sticking, get the valves set .002 tighter than the hot spec. Then oil the cylinders and do a compression test. Make sure you have good spark. Then get the engine up on #1 and make sure the rotor is pointing at the #1 terminal on the distributor cap. Then you can begin to make an informed decision as to your next step. Don

Sorry, my mistake. It never hurts to back track and check over your work. I thought you had, still worth a check, espceially the one where you replaced the pushrod.Larry

Ok thanks

About the compression test, how do I do that? Do I pull all the plug wires off and thread in a guage in a cylinder at a time, and crank the engine to get a reading? I'm assuming I will need a partner to crank the engine so I can read the guage. Never done this before.

Essentially that's all you do.
Yoo don't NEED help really oh just end up running back and forth from the engine compartment to the cab. Look at it as exercise!
Screw the fitting into the spark plug hole, set the gauge on top of the valve cover, and crank the engine. 7-10 revolutions should be plenty, it really doesn't matter as long as you do it the same per cylinder.
The manual says 130psi. Is minimum.

A compression test reall will only tell you if you have compression. It won't tell you were you're losing compression from.
A leak down tester will be more telling.

Before you do anything adjust your valves.
If you are doing it cold add .004 to your measurements.
I= .006 hot add .004 cold so .010
X= .016 hot add .004 cold so .020

The expansion of the valve train is our enemy here you don't want any valves hanging open.
Re adjust them to spec after you've gotten it hot.. Not warm.

My .02

Jeremy

I had a similiar noise and due to a gas leak in the intake manifold, cleaned the needle valve, adjusted the float, changed the gasket and the sound is gone as is the gas leak. Perhaps an exhaust leak may be the problem,just my 2 cents.