The Stovebolt Site Forums The Shop Area Engine Shop Bang Goes the Cam Gear ??

My 46 1/2 Ton Pickup WAS running well till I heard a "Tin" type rattle noise.( only @ 45 MPH or above) Then came the "Knocking" I thought it was a bolt working it's way out of the clutch area, knocking noise went away under load. Then @ idle it got REAL loud and then a bang and the engine shut off. Upon inspection, oil pan off, side cover off, valve cover off, cam gear cover off, the only thing I can find broken is the Fiber Cam gear. I have some parts on the way, Just wondering if any one has experienced this type of failure. To my knowledge this is an original part.I have had the truck for about 30 years and have never had the cam out. Thanks

Welcome to the 'bolt!!

The knocking and banging going on before your engine quit would cause me to suspect something in the valve train, maybe a bent pushrod, stuck valve, broken lifter or something like that caused the cam to eventually bind up and then the gear sheared. Inspect everything thoroughly before you button it back up.

Good luck.

Yes, on my '51 many years back I was moving across state. Driving on the interstate the engine (235) started banging real loud, I pulled over and quickly shut it down. Tried starting it but no go. After towing it to my dad's shop he found the timing gear teeth stripped and that was all.

Fortunately my wife was following me so I didn't get stranded.

Hard to tell which is chicken vs. egg, but as waldo53 said those are the related parts and must be closely examined for damage. In addition: if it's a stuck intake valve, the dome in that cylinder may not have survived, since not much room.

In response to panic, do these engines have clearance. or will the piston in fact hit the valves ? Is it just the intake that would it hit or both ? The push rods are all straight, all the rockers look OK. None bent or broken. Would a stuck open valve cause the gear to strip ? Thanks for the replys thus far !!

Old age alone could have been the cause of the failure of the fiber gear. Doesn't hurt to check everything else while there, but if that fiber gear was over 30 years old, it was time. Maybe even past time.

My bet is when you get the new gears installed, it will fire up and run fine.

Check all the pushrods making sure they are all straight. If the pushrods are all good more then likely the valves are ok as well. Most of the original timing gears "upper one at least" were made of bake a lite. That stuff gets very brittle with age and it is common to hear the knocking before they go south. Im with Roy its probabaly going to live with new gears.

I don't think it's possible to get piston/valve interference on these engines, regardless of where the cam stops. The last time I had a cam gear failure on a stovebolt engine was in 1968, althought I've changed quite a few of them during engine rebuilds.
Jerry

When mine went in a 235 years ago, it just died as I was driving. There were no other noises and no other damage occurred.

bethel, where are you located in PA at?

51 ashton, I'm in Delaware County.

check your pm

I had the cam gear go away on my 235 and it sounded just like what happened to you. My engine was as stock 235 and the valves were clear of the pistons. The engine was stuck and I dropped the pan to see what the problem was. With the cam out of time the crankshaft will rotate around and the crank throws will hit the cam shaft. If you look at the cam shaft you will see flat spots on the cam shaft so when the cam is in time with the crankshaft the throws will just miss the cam shaft while the engine is turning. When the cam gear looses a tooth the cam will be out of time and the crank shaft will start to strike the camshaft as high end of the crank rotates past the camshaft. That noise or banging you hear is the crank shaft hitting the camshaft as it rotates around. On my engine the crank shaft was jammed against the camshaft and would not turn. I had to turn the crank shaft backwards to free up the chrank. I also checked the cam for straightness before reinstallation.

John

John was right on. The Crank WAS hitting the cam. (just nicking it) Minor scuff mark on crank, and no damage to cam. Not quite all the way back together yet, putting new cab mount parts on now. Thanks for all the input.
Paul

Very common thing on the old bolts.They usually go when you are slowing down and the vac wipers will jump up a ways on the wind sheild. These are not an interference engine so there will be no valve train damage.I could change one in 4 hours without removing the cam from the engine.

When I was putting together my 216, one of the rod bolts had an ear missing. The bolt turned a little and when I turned the engine over with a wrench, it stopped with a clunk. The other rod bolt ear was sticking out a little and it was hitting the camshaft. Some things are pretty close in there!

I have a 62 that had the 6 in it. I lost the teeth on the cam gear on the freeway, no noise, no banging, nothing. Engine still turned over fine, but no fire. It wasn't until after I towed it home I found the bad gear.

@retired Wrench - How do you get the old gear off the cam? Mine is stuck on like it's been welded. I gave up and decided to put the 327 V8 I had sitting in the garage into my truck.

I wouldn't mind getting the engine running again. It would be nice to either have a spare, or have an engine I could sell for more than $5.00.

62stick

You break off the fiber till you can get a chisel aimed at one corner of the keyway,a few raps and the hub will split. When driving the new one on you MUST hold the camshaft so it wont go back and knock out the welch plug at the back of the cam. Snap on made a tool for this at one time but you can do it with a bar. DO NOT try this with other engines some have cast shafts and will break. No I didnt but I saw it happen to a Studebaker.This is for 235 and older engines

Heat the gear hub a little with a Propane torch, but don't overdo it to the point you damage the new fiber gear. Make sure the timing marks will line up properly as the teeth roll into place. If you have an air chisel, it taps the new gear on much quicker and more efficiently than hand hammering. Use a 1/2" drive socket the size of the gear hub and an air chisel bit that fits the square drive hole to hammer it on. Pull the fuel pump, and have someone hold the cam forward with a pry bar through the pump hole while you're driving the new gear into place.
Jerry

Thanks guys,

I'll give those tricks a shot.

On the engines I have worked on that have had cam gear failure the oil supply path was plugged. This is common on 216s and 235s.

There is a slot/groove cut in the back side of the timing plate that picks up oil that leaks out the front of the front main bearing. This slot carries oil to the nozzle. This slot is almost always plugged. The timing plate will need to be removed to clean this out.