I am replacing the timing chain on my 69 440 because I was pretty sure it had jumped time. I was driving it and had just punched the gas on the highway while going up a hill to downshift and pass somebody, and I felt some kind of a jerk from the engine. After that it ran bad, as though some of the spark plug wires had become unplugged or switched places. It didn't die, but it was running so bad I pulled it over. It continued to run, but badly, until I switched off the ignition.

Now, I've got everything off and I can examine the timing chain and gears. The chain is definitely stretched, but by turning the crankshaft with a breaker bar, I can get the timing marks to line up (cam sprocket mark at 6 o'clock, crank sprocket mark at 12 o'clock), with the rotor pointing toward the #6 spark plug wire. This is with the chain tight on one side and slack on the other. I expected to not be able to line up the timing marks if it had jumped time.

My question is, if the chain stretches enough, can the chain jump but you can still make the timing marks line up? I played with my new timing set on the bench and it seems like with a little stretch in the chain it might be possible. With a new chain, there won't be much slack, so to see how far off it is now should I rotate the crank gear so there is equal slack on both sides, then look at where the timing marks are?

I had a Ford V8 at work that didnt want to run.Called the Tchain and when I got it apart it almost lined up.It ran like you are saying your did.The dots almost lined up.Changed the set and it ran fine.Id also check your push rods to make sure you didnt pop one.Rocky

well you already have it apart, might as well toss a new chain in. Did you pop the cap and look at your cap and rotor?

To answer your question, no, IF the chain had jumped, the marks would no longer align.

I would try cranking engine over with ignition disabled, and see if there is a dead-low compression sound during cranking cycle. If it sounds odd, like an intermittant freewheeling sound to it, it could be low on compression on one or more cyls. Not very scientific, but is a quick check I've used for years.

put in the new chain/gears, button it up (exc for valve covers), pull the plugs and have a helper hand turn the crank w a breaker bar/1&1/4" socket as you watch the valvetrain assy on each side to see what went wrong. EDIT When you pull the cap check the reluctor vanes. W that audible of a noise something/somwhere collided & we need to find out what

The timing chain can jump if there is exessive stretch. Its even more possible in the case of nylon coated cam gears.
I once had a 74 Duster that ran smoothe but lacked power . The timing chain was a little loose, but was 3 TEETH OFF ! What the heck? The instant rough running condition sounds scary. What if a few valves hit the pistons?

check for bent pushrods

hope no valve are bent

run a compresion check first thing

rule out mech problems,move on to tune problems

look at the plugs when removed for the comp check and make sure they are gaped and not knocked closed

I started out looking for easy fixes, so one of the first things I did was pull the distributor and check it out. The reluctor vanes looked good and the gap was right.

Another thing I did before I posted was pull the valve covers and inspect the rocker assembly. The shaft and arms looked okay.

After I read these posts, I got my son to turn the motor with a socket (there are some good things about teenagers!) and looked at the movement of the valve train. Nothing looked strange, but I didn't really track it around 1-8-4-3-6-5-7-2 or anything. I did spin all the pushrods to see if they were bent and they didn't seem to be.

I didn't think to check the spark plug gap - I will do that next.

As far as anything colliding with anything else, I thought the 440 was not an "interference design," where the pistons and the valves occupy the same space at different times. Do I really have to be worried that a piston-valve collision may have happened if the timing chain jumped? It's a completely stock engine.

Just to be clear, when the problem appeared there really wasn't a noise so much as a feeling, it was more of a jerk.

I had a problem with my wife's 96 Villager van that might be relevant. Oh hell, I guess I can admit it, it's actually my car, I drove it every day until I bought my New Yorker last year; she drives something nicer. It died on me one night and I didn't have any tools to fix it, so I had AAA tow it to a shop that I buy tires from and who I let do some work on my cars. It turns out that my rotor came loose, but they were trying to tell me that in addition to that, the spark plugs were totally fouled out, so they went ahead without my permission and replaced the plugs (at 10 bucks a pop or something). I told them to put the old plugs back and I would come pick it up. It ran terrible all the way home, similar to my 300. When I got it home, I opened the hood and several of the spark plug cables were switched. I fixed that and it still ran bad. I pulled the plugs and they were not fouled at all but the gaps were closed almost all the way. I regapped them and it ran okay after that. Then I bought new spark plug cables and it ran great.

I went back to the shop to give them some honest feedback because I like those guys. I concluded that they must have either tried to close the gaps to get it to run before they figured out it was the rotor, or that they threw the plugs across the room into the garbage can. Either way, they must have changed the gaps. The shop claimed that they had not messed with the gaps. I knew they had to be lying. It got ugly. Needless to say, I will be buying my tires somewhere else from now on.

I suppose it is remotely possible that those guys were not incompetent and/or lying, but I can't imagine how spark plug gaps would close by themselves. But if that happened on my 300, combined with the fact that I had very cheap spark plug cables (which I did), that might explain this.

So go ahead and insult me for not checking that before I let the car sit for over a year and ripped open the front of the engine, I deserve it, but I will be checking those gaps tonight. And maybe I will do a resistance check on my spark plug cables.

did you float the valves when you got down on the throttle passing???

dont think there would be any interferance,but when lifters pump up and hang the valevs open when they should not be...you never know

I have pulled heads to find eyebrows in the top of pistons that were way down the hole

real sloppy chains and over revs/valve float could do it IMO

seen the plug gaps knocked shut also

how?? IDK.but it happens

run a comp check first thing to rule out mech failure

then tune ups