Hi, my 1941 chevrolet coupe makes a very strange screaming/screeching noise.
When idling, the engine sounds fine and runs smooth. But when revving the engine in neutral, this strange noise is coming (I estimate at about 1000-1500rpm), at higher revs the noise disappears.
I took the belt off and ran the engine but the noise is still there, so water pump and generator are not the problem.
Does anybody have an idea what could be the problem?
I’m hearing lots of different noises in addition to the “screech/scream”.
There are some very noisy valves, I think there is an exhaust manifold leak, and I wonder if I am hearing rod knock or piston slap.
When did the noise start?
While you say that it is a stock 216 I noticed that is has a replacement carburetor, I think a Carter YF. So that makes me think there might be some other changes you might not have seen.
One crazy guess is that someone has replaced the fiber timing gear with a steel one.
thanks for your reply! the valves may be noisy because the engine was still cold when I made the video, and maybe this noise stands out on the video more than in reality. The valves normally sound ok to me. I noticed the manifold leak today... I hope this will not get worse... The rod knock like sound, I hear sometimes when this engine is cold and idle speed is very low, but disappears whe the engine is warmed up.
I can't remember when the noise started, I haven't used to car much last months...
The good news is that exhaust manifold leaks are not terribly hard to fix unless studs break. The bad news is that they do not heal themselves.. They do get worse and can contribute to burned exhaust valves.
I definitely would pull the valve cover to check the oil flow to the rockers as well as adjust the valves. Even for cold that is a pretty severe tick.
Depending upon how much sludge you see in rocker arm area you might need to consider dropping the pan and adjusting the rod and main bearings as well as cleaning the pan and oil pump screen.
That might also be a clue to the screech noise. There is a small passage that provides oil from the front of the block to the timing gears. If that is plugged the gears will wear and get noisy.
Hi rusty, The engine is clean on the inside. Since I had problem with oil rings (it was throwing out oil via crankcase breather) I changed the oil about 3 times and used cleaning additives before changing oil. Filter was changed with every oil change as well. I drove about 2 hrs after last oil change and the oil is still clear. I already adjusted the valves and the valve train is clean.
How do I know the timing gears are worn too much? Just by the look of it? by a certain amount of play on the teeth?
I think a knock that disappears when the engine warms up is quite likely piston slap. Most other sources will get louder as the oil thins out. I run a wide valve lash (.010 intake and .017 exhaust) (it's a truck), but my valve noise is pretty much exactly the same cold or hot.
As for the whine/scream, someone else posted something very similar some time back, either here or on the stovebolt site. Don't remember if he followed up with his findings or not, and it may have been on a 261.
It sounds more like x conneting rod bearing.............unless it is a rebuilt engine with aluminum pistons. Iff itis either one I would investigate and NOT drive it. It could be a sludged up engine with oil pump screen plugged up.
Just drive it. If and when it breaks down then fix it. In the meantime don't worry about it.
You may want to have a contingency plan in case it breaks down away from home. Such plan should include a good friend (a good friend is someone who will come toyour assistance even if it is inconvient tothem), towing scheme (chain with length pump pipe, towbar, car dolly or suitable and properly equipped trailer, etc,), a reliable flashlight and some tools.
It sounds just like a good old 216 to me. They are tough.
Not knowing the history of your engine I cannot offer an assessment of how clean it is internally. My experience is that heavy sludge is not dissolved and blocked passages are not cleared by cleaning additives. Think of it this way. If the passage is blocked how can the cleaner dissolve the blockage?
Remember that the oil filter on these engines is the by-pass style, not full flow. Other posts on this forum have estimated that at any given time, only about 10% of the oil flow is going through the filter.
Getting to the timing gears requires that the radiator and the front end of the engine be removed. I’m not sure how much of that oil passage can be cleaned without removing the head.
Have you ever removed the oil pan and adjusted the bearings?
I would agree with Rusty here regarding depending on cleaner additives to remove sludge from an engine's interior. Thanks to the environazis the strength of the cleaners on the market today is so weak you might as well run water through it for all the good you'll get. In an 80 year old engine there are bound to be some areas where sediment has become as hard as cement. Gene's advice is good - drop the pan and check out the oil pump screen and sludge in the pan itself. good luck, and please do let us know what you find.
Good morning to you all, thanks four your thought on this!
I agree on the oil cleaning additives, but the engine looked clean from the beginning, based on how clean it looked under the valve cover. I know this does not guarantee that all passages are free, but my feeling is the engine is clean. I also put my finger through the hole in the pan and there was just normal oil, no sludge.
@ Rusty, would adjusting the bearings cure the screeching sound?
when my 50 styleline had an intermitment knock I pulled the pan to plastigage all the lower bearings, ( which checked fine) I found a small spring in the bottom of the pan. I had no idea where that came from till I rebuilt my fuel pump and found this same spring in the rebuild kit. It goes on the pump arm. the pump arm must have been flopping around at various rpms. after replacing the pump, no more knocks. never can tell what you'll find in there, besides sludge. later, bill
When my exhaust manifold gasket started leaking, it created all kinds of extra sounds. I use a piece of 3/8 plastic tubing to listen to sounds. I can point the end and it is very directional. I could here the valve springs and valves very clearly With my listening device.
Last edited by old216; 04/24/2212:27 PM.
My 1951 1 Ton is now on the road! My 38 Master 4 Door is also now on the road .
I'd forgotten that I had a pump spring break on a 350 and cause a knock. In that case however, it sounded more like a collapsed lifter than a lower end knock.
As for the screaming/screeching, on second listen it actually doesn't sound much different than a 230 cid six we still have. It just always sounded like that. :-) So I wouldn't worry much about that part.
The heavier knock is another matter. I still think a rod knock shouldn't disappear when the engine warms up as you say it does.
I really cannot offer much more advice than has been presented. There is a lot of excellent guidance being given.
The reality is that it is almost impossible to cure an internal engine noise without going inside the engine to find the source.
My assessment is that you have essentially 2 choices. One is Charlie’s recommendation to keep driving it as is and have a tow on call. The big variable in that choice is the amount of collateral damage done when things do fail.
The other is to bite the bullet. First drop the pan, then decide if you also need to pull the timing gear cover.
A big factor in this is how much you plan to drive the car and how long you plan to keep it. If all you do is make a trip once a month to the ice cream store you might want to consider Charlie’s guidance. If you use your car as your daily drive like I do, you might want to make the more difficult choice.
I guess the knocking sound may be piston slap as is disappears when the engine is warm, like somebody mentioned in this thread. It cannot be the fuel pump since I removed it and run an electric pump. I will drive the car for a couple of hours and see how the noise develops. I am going to an event about 230 miles away next week, so no time (and parts) to take hard things apart. If the noise stays as it is, I'll take the risk and look deeper into the problem when I am back home...
A loose rod will make no noise with cold oil. After 15 minutes of the engine running, the oil will thin out and it will make noise. it will make no noise at idle but will under load.
A burnt out rod will make noise cold due to the missing babbitt.
An original cast iron piston usually will not suddenly make noise unless it is Zero degrees weather. An aluminum piston commonly can make noise and will go away after a few minutes unless the skirt is broken or ?
Also, to check out engine noises, the throttle must be teased and run at higher speed and cylinders shorted out in the process.
It is difficult to diagnose noise on recordings.
The general sound of the engine indicates it could have several problems.
One thing I am sure of is that I would not take it on a 200 miles trip.
I would make the trip. I would have a friend standing by in case I need to get it back home. I would drive it near the minimum stated speed for the road, say 45-50 MPH.
I would choose Interstate highways as much as practical and drive in the right hand lane and only pass when coming up on slower traffic, saya 37/38 a-poking along. You know.
I would pack my tools and cary spare parts as much as practical. You know, do it the Boy Scout way.
The trip is an opportunity for adventure in that it might have you on edge for the first thirty minutes or so but that anticipation of disaster will fade as you journey along and you will enjoy the trip. Adventure, by definition, is not fun while it is happening. But this trip it could be. Could too!
My bet is that the engine will hold up very well and you will have good memories of it afterward.
Best and good luck with the trip.
Charlie
BTW: Check everything out before the trip and remember that the friend and contingency plan are essential anytime we make a significant trip on our old cars. Especially the friend who you trust will come to your aid, if needed.
BTW2: Don't overdo the contingency plan part or you will erode too much of the sense of adventure and its accompanying great memories.
BTW3: Make sure your horn works so that if you do come up on a 37/38 then you can startle the heck out of them as you blow by. Oh, yeah!
Hi Charlie, I started the trip yesterday and I arrived well! I drove 230mi and I drove it 5 hours straight. The engine used a bit of oil though, I started with the dipstick on max and after 230mi it was on min. I had to refill about 0.5l (0.5 quarts). It still sounds like it sounds:). I drove at around 50-55mph since trucks drive this fast here in Europe. Driving slower would mean they all have to overtake me (police won't like this). They only problem I had was that the transmission started popping out of 3rd gear, but I will start a separate thread about this.
Thanks for your motivation talk! :) Please prey for me next Sunday when I'm driving back home!
Just keep her well oiled and sufficient coolant and I expect it will get you home just fine.
You're in my prayers to make a adventurous and safe trip home. Yep.
Best,
Charlie
BTW: Give us a post when you get back.
BTW: The popping out of gear will likely increase in frequency. Is the gears fully meshed or is the linkage off a bit. I would investigate the before starting back. I had a 41 conv. doing that to me on the way from NC to Erie,Pa way back when. Got to where it wouldn't and couldn't be held in drive. Then second started doing the same thing. Ended up having to leave it in western PA. Got back from Erie and guy I left it with helped me pull the transmission and fix it good enough to get back to NC. Talk about adventure, I have had some with my old 41s.
Thanks for asking, I made it home without any problems. In total I drove about 650mi without any major problems :) !! Because the transmission was popping out of gear at highway speeds at high load, I skipped the hilly part of the Autobahn and took a scenic route along the river Rhine. No problems whatsoever, it is like this car is made for these kind of roads. I added a picture of the car at the famous Lorelei in the attachment... (https://en.wikipedia.org/wiki/Lorelei)
The engine noise is still as it was before. I think I will take off the camshaft gear cover to see if the gears are lubricated. Also I will clean/rebuild the carburator since it seems it is not working perfectly. I will also look at the transmission again (linkage, allignment, pilot bearing). Also I will get rid of this rubber steering dampener, this thing flexes too much!
When I have more information about the engine noise, I will let you guys know...
They are tough. 
