Woohoo! Finally jumped my timing chain!

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MopaR&D

MopaR&D

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I was driving my '70 Duster 318 out of my school parking lot today and it all of a sudden made a small weird sound from the engine and promptly stalled. When I tried to restart it it sounded as though it had no compression and would pop through the carb. Is my timing chain broken/skipped? If it did, is it possible that I smashed up any of my valves? It's a totally stock (internally) 318 2-bbl. with about 120,000 miles. I towed it home with the help of my buddies and am about to start gathering resources. I know I'll need a damper puller, a degree wheel, and a dial indicator. Is there anything else I might need?
 
A degree wheel,:happy8: I have never used one on a stock motor.
I just put the new timing set in and align the dots.:cheers:

I wonder if you have a nylon gear in there.:sign7:
 
If this is a stock engine and you are not replacing the cam you don't need the degree wheel or dial indicator. A sharp razor blade scraper, a small amount of good silicone seal, maybe some copper coat spray for your gaskets. This is a good time to install a new water pump and belts as well.
 
I don't need a degree wheel even if the cam timing is now off? Also, about how long might this take me (hour-wise) to complete with the engine in the car?
 
MOPEkidD-3 said:
I don't need a degree wheel even if the cam timing is now off? Also, about how long might this take me (hour-wise) to complete with the engine in the car?
Click to expand...

No you don't need a degree wheel or dial indicator with stock stuff. Just do like Mike said and slap a new chain and geaars on it and align the dots and yoru good to go.

Estimating time to repair is hard to nail down cause every working condition is different. I can do one in 2-1/2 to 3 hrs but I have air tools. If you do it with regular hand tools figure about 4 hrs.

I doubt you hurt any valves. I've had a couple jump on me and not hit anything. SB Mopes have a ton of clearance. Just to be safe though I allways put on the new chain and spin it over and see it there's compression on all 8.
 
check for bent valves anyway. a number of years ago my '71 Charger with a stock 318 pulled a few teeth off the cam gear and it bent an intake valve. its cheap insurance so you don't damage anything else.
 
Before ya go tearing down the engine only to find it's not the timing chain try this. Remove the mechanical fuel pump then turn the engine over, in normal rotation, using a socket and rachet on the end of the crank, 1/2 turn should do the trick. Disconnect the battery then reach in the hole in the side of the chain case, that the fuel pump occupied, and in around the corner you'll feel the timing chain. It should be fairly snug and not flop back and forth more than a 1/4". This will be the slack side of the chain as long as you turned the crank over in normal rotation.

Terry
 
Or another one is to pull the number 1 plug and crank the motor till you feel compression, then line up the timing mark on the balancer and pull the cap and see if the rotor is pointing to the number one tower. Even if its off only a couple teeth the rotor will be sitting between the towers or on the wrong one.
 
If the timing chain broke couldn't he just pop the valve cover and bump the starter to see if any valves are moving?
 
the problem is usually the chain doesnt break. most times it is the stock cam gear is made of a phenolic material that breaks or chips off over time. this causes the chain to slack and it can slip off by a few teeth or break a large section then if it drops to the pan then the oil pump can pick it up. if that has happened you might have a really big problem.
 
Easiest and quickest way I know of to check for bent valves is to pull the pushrods and chuck them in a drill. If one is bent you'll know it. No bent pushrods, no bent valves.
 
camd64 said:
the problem is usually the chain doesnt break. most times it is the stock cam gear is made of a phenolic material that breaks or chips off over time. this causes the chain to slack and it can slip off by a few teeth or break a large section then if it drops to the pan then the oil pump can pick it up. if that has happened you might have a really big problem.
Click to expand...

That's true and something I'd forgotten. The 383 I had as a kid did this and the oil pump pickup was nearly plugged shut cause of the nylon crap.
 
Another way to check the pushrods is to roll them across a flat surface, if they wobble then they are bent. Check the cam gear carefully to see how much of the nylon blew off. If its not too much of it missing (a tooth or two), I wouldnt worry about it getting into the oil pickup.
 
I am sure that you are already aware of this, but if you hadnt done so already, I would install a double roller setup with steel gears to prevent this issue again, or at least for a very long time.

They actually wont cost too much more than an OE replacement link type chain.

-Justin
 
Well, I finally got to my chain, and to my dismay I found the entire cam sprocket to be SHREDDED. All the teeth were basically gone. I'm guessing now I'll have to do an oil + filter change before I start my engine again if I don't want my oil pickup sucking up pieces of aluminum and nylon (WHY did they use this!??).

P.S. I got a nice COMP Cams Magnum double roller timing set to put back in.

EDIT: And another thing, would I get any benefit out of advancing/retarding my stock cam? I wanted to swap my cam when I did this repair but don't have enough money right now.

Here's pics:
2d38bded49fc.jpeg


a4c3f8b910b9.jpeg
 
you need to drop the pan ,to clean out the trash .....a oil filter change will not catch the trash....it will go threw the pump first...........you also need to check for bent valves ....try the above.....pull the valve covers and look for bent push rods ...good luck..
 
MOPEkidD-3 said:
Well, I finally got to my chain, and to my dismay I found the entire cam sprocket to be SHREDDED. All the teeth were basically gone. I'm guessing now I'll have to do an oil + filter change before I start my engine again if I don't want my oil pickup sucking up pieces of aluminum and nylon (WHY did they use this!??).

P.S. I got a nice COMP Cams Magnum double roller timing set to put back in.

EDIT: And another thing, would I get any benefit out of advancing/retarding my stock cam? I wanted to swap my cam when I did this repair but don't have enough money right now.

Here's pics:
Click to expand...

Wow!! I've seen bad ones but that's the worst. The post above by kennmadruga is correct about needing to drop the pan and clean out the trash. An oil and filter change won't help one bit cause the oil pump screen won't allow it through and it's a good thing it won't cause it'd trash the pump if it did. I guarantee all that nylon crap that came off the gear is sucked up against the oil pickup and partly closing it off. Try breathing through a straw and that's the effect it causes with the oil pump. It'll starve the system for oil if you don't clean it out and you know what that means. Say bye bye to the motor in no time.

Advancing it 4 degrees might help torque some but it'll make it top out at a lower rpm. I did that on a 350 chevy when I was a kid and it did help it allot. Might be worth trying since you can get the 3 way gear sets cheap.
 
Damnit! Is dropping the pan a big chore? Now I'll have to spend even more money on an oil pan gasket. And with my luck, it'll probably leak like a sieve when I'm finished putting it back on (like my tranny pan that I've dropped 3 times to try to stop from leaking). I was hoping I could just empty the oil through the drain plug and wash down the debris by pouring oil down the front of the pan (although I doubted that would work because most of those chunks probably wouldn't fit through the oil drain plug).
 
those pictures are exactly why no matter many miles are on those timing chains you need to get thos plasice things out of your motor. my 360 had 48,000 miles and the gear was cracked.
 
1. It is possible you bent valves, without bending the pushrods. In fact it is highly likely. I've been there myself. I'd do a compression check as soon as you get the chain back on (before you put the cover on, fill the radiator, etc...).

2. It is possible you also bent pushrods. Been there myself.

3. The teeth on that cam sprocket have been coming apart for a long time, they are quite possibly all sucked up onto the oil pump pickup screen, along with your original valve guide seals. Been there myself.

4. If you've bent a valve, you will probably need to do a full valve job. Guides, seat resurface and multiple new valves. No real point in pulling the heads and doing a half-assed patch job.

5. If you have the heads, intake and timing cover off, a cam swap is easy. At minimum I'd take a look at your lifter faces for wear. I bet they are starting to dish.

6. If it sounds like it would be easier to pull the motor to do this, it is. You'll be able to CLEAN parts and will stand a better chance of getting a good seal.

7. If your compression is still good, just run it. Your engine isn't quite worn out yet. Save up for a rebuild in the near future.
 
Since you have the front cover off to swap the chain already, you have a start on dropping the oil pan. I think you can drop the oil pan with the engine in the car if you drop the center steering link first. You may also need to disconnect the motor mounts to jack up the front of the engine.

Make sure the bottom end of the engine is VERY CLEAN before starting. You sure don't want to knock a piece of grit into the oil pan as you button things back up.

Concur that you have the most messed up cam timing gear I have ever seen.
 
This sucks. I honestly want to just give up right now. I don't understand how my valves could possibly bend with big open chambers, pistons deep in the holes at TDC, and a max valve lift of .400". When the timing chain jumped the engine shut off in a split second but now that I think about it I did hear a very light weird noise, not necessarily a "grind" but not really a "bang" either. I don't know what the HELL I'm going to do, I definitely don't have the time or resources to pull my engine and go through the top end. I wish somebody in my family could help me and I had some freakin' tools besides a socket set and jack.

UPDATE: I turned my engine over by hand with the timing set put in and I definitely felt compression at (for the most part) normal intervals. I suppose I'll have to hook my battery back up and do a full compression test on all 8 cylinders (****.).
 
Yeah, you might have gotten lucky. I didn't. Mine let go at speed, so everything spun for a few revolutions out of timing.
 
I was pulling out of my school parking lot doing about 1600 RPM in first gear and I was accelerating at a leisurely pace, if that means anything. I would be much more worried if I was doing 80 MPH down I-25 pulling 2700 RPM in third gear or making a "heated" getaway (before now that's all my 318 could muster).
 
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