[nanl2053]

Hi Guys,

I have a 69 RoadRunner with a 383. I set the timing and took it out for a drive around the block and it stalled / died under light acceleration and wouldn't start. After being towed home I turned the motor over with the distributor cap off and the distributor doesn't rotate. Shining a flashlight down the shaft I can see the cam is not turning when I crank the engine over.

I'm thinking the next step is to tear down to the timing chain. If the timing chain did break, what kind of damage am I looking at? I can't recall if the 383 is an interference engine. Do I need to pull off the heads and inspect them?

 

[dana44]

Welcome to the forum.

Remember all those engine build-ups where they put clay on the top of the piston and crank the engine over to make sure the piston and valves have clearance? Good chance this same thing was happening in the clearance department when you were at the stop sign. With that, yes, might be time to pull the timing cover. To save just a little bit of diagnosing, grab the bottom pulley and rock it back and forth to see if the cam will move at all, or if you can hear the chain ratting when you turn the crank, which would be quite an indicator or a broken chain. Some of the possibilities you have going for you are a simple woodruff key broke, the cam bolt came loose and sheared the pin on the camshaft nose itself, or the camshaft itself broke, all things that have happened in the past to others.

Once the actual problem is identified, need to figure out why it happened (a primary reason it occured ), then we can talk repairs, and lastly, do a compression test at the end just to verify nothing bent in the heads. Just because there is supposed to be clearance doesn't mean there always is clearance.

 

[nanl2053]

Thank you dana44. That makes me feel a little better. I'll poke around some and report back with what I find. The only thing that changed right before this happened was timing, could that be the root cause?

 

[dana44]

No, don't think just changing the timing did it. It's one thing when the distributor itself isn't turning, another thing when the camshaft itself isn't moving. Has to be a break of the woodruff key, pin on the camshaft nose, chain breaking, doubt it was teeth on the cam breaking (they usually just skip a tooth and are rarely nylon teeth on a Mopar), or break of the camshaft nose at the first cam bearing for the cam not so be showing no movement. If the cam were moving but not the distributor, it would most likely be the intermediate shaft to the oil pump, but you said the cam was not moving.

 

[nanl2053]

A mere 9 months later I finally got around to pulling off the timing chain cover. The problem is obvious but I'm baffled by the cause. The timing gear was hanging loosely around the bolt that threads into the end of the camshaft. I assume there is supposed to be a washer that holds it tight? If so, there's no sign of it, although it could have fallen down into the oil pan. Any idea how this could have happened?

http://imgur.com/ZkfDrQE

 

[KOG]

Take the bolt and and look to see what happened.

 

[nanl2053]

I didn't even need to take the bolt out because the gear easily comes off over it. There is no sign of damage but it almost looks like the came shaft isn't sticking out far enough? If I put a washer on it and bolted the gear back in place it would be touching the block. Is there supposed to be a spacer or something?

More pics: http://imgur.com/a/Q0G9O

 

[GLHS60]

No spacer between the block and cam gear. The notch in the block is there so oil can lubricate the surfaces.

Thanks
Randy

 

[tazdevil]

A good friend had a somewhat similar incident. His engine builder found that the cam journals were out of spec in diameter on the oversized side Ugly results! The cam seized in it's bearings.

 

[Tweety Bird]

Lots of people here who are far more expert than me, but here's how I understand it: The back of the timing gear is supposed to run against the block. The flat tappets run against tapered lobes which provides a thrust to the rear when the cam is turning, so the cam doesn't work back and forth while running.

If the cam seized, the dowel would be sheared or severely damaged, as would the timing gear. I don't see anything catastrophic in the photos to indicate that.

When the bolt came loose, I think the cam simply walked to the rear because of the thrust on the lobes. Put the bolt back into the cam and I bet you can pull the camshaft forward a bit.

Edit: I just noticed the link to your first picture. There should have been a thick flat washer between the bolt head and the cam sprocket. I'm amazed it ran for any length of time at all without it.

 

[nanl2053]

Thanks guys. If I put the bolt in the nose of the cam it rotates fine and the valve train seems to work smoothly so I don't think it seized. There is no way it could have run without the washer because the hole in the timing gear is bigger than the head of the bolt. Is it possible the bolt came loose and the washer broke or wore through? I don't see any signs of damage or scraping and that washer looks pretty thick in the pictures I've found.

 

[Tweety Bird]

The bolt doesn't take any torque when the engine is running; that is, the cam isn't relying on the bolt to make it turn.

The bolt and washer simply hold the cam sprocket in place against the front face of the camshaft. The locating dowel and the friction between the sprocket and cam are what provide the torque to the cam. And since the bolt head is smaller than the hole in the sprocket, you had nothing securing the sprocket to the camshaft.

The engine would run without the washer as long as the sprocket remained engaged to the face of the cam and the locating dowel. But I can't see how it would run long before the cam worked its way rearward and disengaged from the sprocket. In fact, it seems to me that this would occur the first time you tried to even crank the engine.

How long has the engine been assembled? Was it a fresh rebuild? I'm guessing that washer was never installed but it's a mystery to me how the engine ran at all without it.

I can't see how that thick washer could crumble, break up or just disappear. I suppose it could have been fractured and the pieces are in your oil pan. If possible, you might see if you can fish around inside the oil pan with a magnet on a stick to see if you can catch anything.

This is a weird one.

 

[nanl2053]

The bolt doesn't take any torque when the engine is running; that is, the cam isn't relying on the bolt to make it turn.

The bolt and washer simply hold the cam sprocket in place against the front face of the camshaft. The locating dowel and the friction between the sprocket and cam are what provide the torque to the cam. And since the bolt head is smaller than the hole in the sprocket, you had nothing securing the sprocket to the camshaft.

The engine would run without the washer as long as the sprocket remained engaged to the face of the cam and the locating dowel. But I can't see how it would run long before the cam worked its way rearward and disengaged from the sprocket. In fact, it seems to me that this would occur the first time you tried to even crank the engine.

How long has the engine been assembled? Was it a fresh rebuild? I'm guessing that washer was never installed but it's a mystery to me how the engine ran at all without it.

I can't see how that thick washer could crumble, break up or just disappear. I suppose it could have been fractured and the pieces are in your oil pan. If possible, you might see if you can fish around inside the oil pan with a magnet on a stick to see if you can catch anything.

This is a weird one.

We bought this car from a friend over 10 years ago and haven't done anything but change the oil. It's driven occasionally probably

 

[Tweety Bird]

No, without the bolt and washer the cam should simply walk backwards (like it did) and disengage itself from the sprocket. If it was mine, I'd thank my lucky stars that it happened at idle rather than 4500 rpm. That might have been "interesting".

Can you get the pan off easily? I'm betting you won't find the washer in there but I also don't know how it could run without it unless somebody put a roller cam in there (which doesn't have any lobe taper). Any sign of damage to the inside of the timing cover?

 

[chuzz]

Seems to me that the oil pan is the only place that washer could be, if indeed it was ever on there to start with. I haven't worked on a big block Mopar engine since 1975, though, so I am most likely very fuzzy in my recollection of the way the opening to the oil pan sits in relation to the timing gears. I seem to recall and opening that could be large enough to allow that washer to fall into the oil pan. Oh well, let us know what you find.

 

[68RT]

Opening is large enough to swallow more than the washer but the bolt would have to come totally out for the washer to come off unless it split and then it would drop harmlessly into the pan. Since you will have some access you might be able to fish it out with a magnet.

 

[Tweety Bird]

Did you ever find the washer in the pan? I sure would like to know what was going on with your motor.

 

[Rick Anderson]

The bolt doesn't take any torque when the engine is running; that is, the cam isn't relying on the bolt to make it turn.

The bolt and washer simply hold the cam sprocket in place against the front face of the camshaft. The locating dowel and the friction between the sprocket and cam are what provide the torque to the cam. And since the bolt head is smaller than the hole in the sprocket, you had nothing securing the sprocket to the camshaft.

I "thought", but I could be wrong, its the opposite. The locating dowel is just that, locate the cam sprocket on the cam face with the correct timing. The clamping force from the nut and washer clamping the two together, actually bears the torque load of turning the cam, that the dowel itself would shear off at any higher rpm or stress.

I know for a fact that is true for some later engines, I might be total wrong for the earlier B/RB engines. Regardless, I think everyone agrees that its a miracle that dowel didn't shear off, and the correct thing to fix it is to get a "proper washer" and torque it to spec.

I would NOT use any old bolt and washer from the hardware store, I would get the specific bolt and washer for the engine, in fact this is what a google search turned up.
http://store.440source.com/Bolt-kit-Timing-Chain-to-Camshaft-Single-bolt/productinfo/109-1510/

These have been long discontinued by Chrysler, and we couldn't find them anywhere, so we reproduced the unique washer and sourced the bolt in a super strong grade 8 version. These fit all years and all engines with single bolt sprocket. Will not work with 3 bolt cams.

Hmmmm, so is it possible the original rebuilder couldn't find the specific washer and used some generic washer from the hardware store to cause this?

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On a related note, the latest API/SAE spec (SN) for motor oil, has dropped EP zinc additives for high impact wear resistance. This is because all the motors of last 20 years all have roller cams in them and the zinc in the oil shortens the life of O2 sensors and Catalytic Converters. Tappet/Lifter Cams need the EP Zinc additive for the metal to metal impact and wear.

What I've read, if the cam is already broken in, the lack of zinc won't increase the wear to much to cause problems. But if the cam is brand new, using the latest API/SAE spec oil will result in the cam wiping tappet/lifter and cam lobe faces right off.

Some of the "High Mileage" versions of popular brands of oil have the API/SAE (SM) standard, (you want to look it up, I'm pulling the standard designations from memory, so I could be wrong), and thus have the zinc for tappet/lifter cams. You can also buy zinc additives to pure into the engine after an oil change as well.

BUT, this is just info for the future, you've already stated the cam is moving fine and the problem was NOT the cam seizing up, but the bolt washer coming apart, so it wasn't the oil that caused your problem.

 

[Tweety Bird]

Yeah, you're right about the locating pin. I was focused on - and trying to say - that the bolt itself doesn't take the torque load. Sometimes my fingers and my alleged brain don't remain fully engaged.

I wish he'd come back and tell us more on what he found in there. It's a weird one, indeed.