The Stovebolt Site Forums The Shop Area Engine Shop 235 Noise Issue (1954)

Hello and greetings from the Great Northwest!: I have a 235 in my 1953 GMC that came out of a 1954 Belair (per the seller). Runs great! But I am getting a high pitch squeeling type noise, on and off (but mostly on). Thought it was front end stuff (belt, water pump, alternator) because it seemed to come from the front of the engine. But today I removed the belt so nothing was turning and the noise was still there. I took off the valve cover to check the oiling. Seems like reasonable oil drippage from rocker arms and shaft. I oiled the whole rocker shaft with a hand oiler very thoroughly and the noise did not go away. I seem to have about 40 psi oil pressure (but I have had that remote gauge for many years and it could be inaccurate). So I don't know. I am hoping some of you more experienced 6 cyl folks might have an idea or have seen this before. Thank you very much! Dave (Snohomish Washington)

Check your clutch adjustment. It the throwout bearing is spinning all the time it can begin to lock up and squeal. You should have 3/4"-1" of free pedal travel at the clutch before you feel the bearing contact the pressure plate fingers.
Jerry

Need to try to isolate it (get an idea where its coming from). Use a hose or mechanics stethoscope. Distributor ?

Thanks Gents!

Funny story. I had breakfast with a friend this morning. Was telling him about my noise issue. He said, "Dave, you need to get a stethoscope and try to pinpoint it better". Then he thought for a minute more and said, "its probably your throw-out bearing"! Imagine that, exactly what the experts here said!

But back to business. I did adjust the clutch free play, which it needed. But still had the noise. I got out a stethoscope and started listening around. The stethoscope really starts screaming when I touch the timing gear cover. So it seems it is definately something in that area. Any thoughts or suggestions on how to proceed? Thank you very much!

Dave

Two possibilities- - - -a timing gear that's rubbing the cover (not likely) or a front main bearing. There's also the possibility that the damper ring on the crankshaft balancer has come adrift and is rubbing the outside of the timing cover. Time for some major surgery, beginning with pulling the balancer. It's a press fit, and will require a T-shaped puller bolted to the balancer to remove it. Once that's done, run the engine for a short time with the balancer off. If the squeal is still there, pull the oil pan and the timing cover and inspect the gears. Yes, the oil pan must come off- - - -the two bottom timing cover bolt heads are through the bottom of the front main bearing cap with the heads inside the oil pan. Yes, there's a good reason for that.
Jerry

I did the cover mod to put the bolt heads on the outside last weekend. NOW YOU TELL ME THAT THERE IS A GOOD REASON TO NOT DO THE MOD. What is the reason?

Thanks Hotrod! I will get that disassembled. What is my worse case scenario and what will it take to correct it?

The two bolts on the bottom were put in that way to make adjusting the main bearing clearance on the #1 main bearing easier do do by changing shims. It could be done from the bottom by removing those two timing cover bolts without pulling the damper and fighting to access those bottom bolts. Since the 1955 second series engines came along that don't use main bearing shims, the direction of the bolts is a moot point- - - -there's virtually no reason to remove the timing cover between major overhauls that require pulling the engine, and the timing cover seal can be changed with the cover in place if necessary. Even that would be highly unlikely other than some sort of foreign object damaging the seal. Unless you put 5/16" heli-coils in the main bearing cap holes, it's necessary to use 3/8" bolts at the bottom of the cover- - - -definitely overkill!
Jerry

Just more brain storming, a dry or bad seal might do that, I have never had that happen though.

The worst case scenario would be a scored front main bearing or cam bearing. Either one of those gets into major rebuild territory. If something looks shiny, like the inside of the timing cover, it's possible a little sheet metal massaging might cure the noise. While things are apart it would be a good idea to look at the clearance on the rod and main bearings. Good luck!
Jerry

Thanks. I don't need to worry about shims - is a GMC 302.

I took the dampener off, put the radiator back on with coolant and ran the engine. I let it get fairly hot and I could not get it to make the screeching noise. I can't describe it but something doesn't sound right in that cover area. Kind of like a slightly loose or vibration-y sheet metal type noise when I gave it throttle. Dampener seems fine but there is a noticeable wear mark on the OD (the ~1.6" OD where it goes into the cover) that is about .4" fwd of the aft edge. Next step? Thank you!

Dave

There might be an oil slinger inside the cover that can rattle around once the damper is removed. Does the wear mark correspond to the position of the sealing lip of the seal in the timing cover? If so, a "speedy-sleeve" for a small block V8 is the same size as the stovebolt damper hub, (1 3/4" OD) and it's stainless steel- - - -much more wear resistant than the soft steel hub snout. I'd suggest dropping the pan and pulling the timing cover just to do a good job of inspecting the timing gears, etc.
Jerry

Thanks for helping me, and for taking the time to teach me!! I will pull the pan and cover tomorrow. It is bothering me though that the squeeling noise went away when the damper was removed. Does that lead you to a likely cause? If it was a bearing issue would you expect it to continue after removing the damper? Also the high pitch squeel could be characteristic of a sheet metal issue. I don't know. The seal seems to be in place, and yes the wear mark seems to be at the seal. The wear mark is very minimal, just barely able to catch your finger nail. Would you expect any oil to be thrown out of the seal hole with the damper removed and engine running? That damper did not come off easy, how will I get that pressed back on?

Dave

Davegmc1 An oaken 2x2 big hammer,have a helper keep the crank pried forward each blow,however I didn't do that on my 235,don't have to kill it just drive iton ! Will be able to tell when it bottoms out. May have to use a punch thru the crank hole if 2x2 wont go in there,pad the balancer with wood or brass. I have sat on the head surface and used the hammer but it will bruise the balancer,that was as a young mechanic 60 years ago.

Hello: I removed the oil pan and front cover. Not sure exactly what to look for but everything seems okay. Timing gears seem fine. Cover seems fine. Oil seal has been leaking but is completely intact. Looking for advice on how to proceed. Can't see anything that looks like it would cause the high pitch screaching. Thanks!


Dave

Getting the damper back on is a bit of a challenge, since it needs to be driven on with a big hammer, or pressed. To prevent damaging the thrust flange on the #3 main bearing, remove the sheet metal splash pan under the flywheel and drive a hardwood wedge between the clutch pressure plate and the bell housing to hold the crankshaft forward, then use a wood block and a big hammer to drive the balancer on until it bottoms against the timing gear. Removing the radiator usually gives you more room to swing a hammer without doing any damage. Be sure to change the front seal in the timing cover before replacing the cover. The seal is the same size as one for a small block Chevy V8. If the score mark in the hub isn't deep, just shoeshine it with a length of emery cloth to polish away any rough spots. If there aren't any shiny spots on the inside of the timing cover or on the perimeter of the balancer, I have no idea where the screech might be coming from. Did you remove the front main bearing cap and inspect the bearing? Since the noise goes away with the balancer removed, the bearing isn't likely to have a problem, but with the oil pan and timing cover off, now would be the time to check it out!
Jerry

Jerry: I took the main bearing cap off. Bearing lower half looks pristine. Plastigaged at .0015 or less. I will go ahead and put it back together. Problem is I did not find any issues, and I am not correcting anything except changing the seal. Do you use a centering tool for the cover (seal area) as the manual suggests? Also, do you change out the slotted head fasteners for something easier to work with (pan and/or cover)? There is a brass nipple protruding from the timing gear plate. Must be an oiler. Do I need to check that and make sure there are no issues with it? Regrettably, I have no idea who owned this old engine and who worked on it before me? High school kids? Thanks again!

Dave

The oiler tube has a spit hole that should point at the intersection of the timing gears. It's more important if the cam has a fiber gear which was used on passenger car engines, as those are more prone to wearing out than the aluminum gear used on the truck engines. The fiber gear runs a little quieter. I've always used an aluminum gear on a rebuild, as the extra durability offsets whatever slight increase in noise there might be. The cover bolts are 1/4-20 thread, so you could substitute regular bolts for the "stovebolts" that give the Chevy six its nickname.

I used to fabricate and sell a crankshaft snout drilling and tapping jig that used a 1 1/4" ID milling machine spacer as a centering device for hardened steel drill bushings, and also served as an alignment jig for installing the timing cover as its OD was the same diameter as the balancer hub. It had a keyway broached into it that allowed it to fit over the crankshaft snout without removing the Woodruff key. Even without the fixture, the cover alignment should be pretty close. You can always leave the cover bolts a little loose, and tighten them once the snout of the balancer enters the seal, before driving it all the way on. It's a bit tricky to do that with the engine in the frame, but not impossible.

Reassembling without finding a definite problem is always worrisome, but you might have "fixed" the problem without actually discovering the root cause. Good luck!
Jerry

Just asking here, but with the balancer removed my assumption is that the fan belt was also removed. Any chance this noise was coming from the water pump and carrying (for lack of a better word) over to the cover area mimicking a noise from the timing cover? Maybe the belt was too tight making the pump bearing scream a bit?

I can't find a cause Dragsix. When I started chasing this noise, I replaced the alternator, water pump and belt. Still squeeled. Then I ran it with the belt removed so nothing up front was moving. Still squeeled. Didn't seem to squeel when I ran it with the balancer removed. I have not put it back together yet.

I would like to do the timing cover bolt mod. Wondering if you guys think that is a bad idea? In looking at this, the existing holes in the bearing cap are about 11/32 (.344 ish). This is about 1/32 (.031 ish) over the tap drill size for 3/8-16. So I'm not going to have anywhere near the full thread depth for a 3/8" fastener. Going bigger than that could create clearance issues, not sure. So I'm wondering what experience others have had?

Thanks
Dave

How often do you intend to remove the timing cover without disassembling the rest of the engine? Stovebolt timing gears last about 3 days past forever- - - -I've seen 50+ year old ones going strong with minimal wear. The timing cover seal can be changed from the outside without removing the cover. If you simply must make a change for some reason, why not tap the main bearing cap for a 5/16" helicoil and simply drill the threads out of the timing cover for a 5/16" bolt? The hole in the main cap is just about the right size for a helicoil tap already. I can't seem to dream up a good reason for changing from the original design since removing the timing cover is done so seldom.
Jerry

I have done the mod for every motor I have built over the last 40 years. Do not use a lock washer or stainless bolts, or anything harder then a grade 5 bolt. Use a tiny bit of pipe sealer on the bolt and snug down. All the years I did this, I never had to take the cover off. In 2015 I finished up the 261 build I was doing. Very modified motor. Two months after it was running, I discovered my timing cover gasket was leaking. I also always drill and tap my crank snouts for a bolt. So it was an easy repair (btw, installer error, I apparantly pinched the gasket on install). Loosened up the front motor mounts, jacked the motor up a bit for clearance to get the balancer off, remove the balancer, remove the timng cover, replace the gasket, install the balanceer with a balancer install tool, reinstall the balancer bolt and put it all back together. Man, was I grateful I had made those mods. Made that repair so much easier.