Do "jumped timing chains" really happen?

[Dave Young]

I'm chasing a problem on my 28 Chandler.  After finally getting it running beautifully, an abrupt change occurred while driving and now I'm getting backfires thru the carb, hard starting, low power and heat.  This is a straight 8, dual point ignition engine.  It ran poorly when I got it a year ago.  Better carb, manifold fixes, vacuum tank, relined brakes, and other external improvements made her purr right along.  I'd say that I've put maybe 1500 miles on it lately.  After exhausting the usual diagnostics such as fuel and ignition, I'm left with the conclusion that the valve timing may be off as the result of the Morse chain being too loose and jumping a tooth on the cam.  Does this occur?  It seems so unlikely given the diameter of the cam sprocket.    It looks like quite a task to get at it on this car.  Luckily, I do have a new chain on the shelf for my other Chandler which I am I the process of rebuilding.  I'm not looking forward to this one.  I've got my Model T engine almost done, my T Pickup was next on the list for rebuild, and the Chandler "all done".   Funny how my 29 Model A just never seems to have ANY problems!  The dependability of the Model A is simply uncanny.  Too many cars for a guy who isn't retired!

[Owen_Dyneto]

Yes, it can and does happen.  However, for every 100 times that someone has a problem and suspects that the chain has jumped, I'd guess that 99 of those times the problem was elsewhere.

[Dave Young]

Great odds!  My first plan of attack is going to be to pull the manifolds and head.  Then pull the  valve cover plates and check that the valves are in fact closing at the correct relationship to piston travel.  It's a bitch that I just put those manifolds on there with brand new, very difficult to find, copper clad gaskets.  The head is held on with studs... a million of them, and we know how difficult it can be to get that head to move upward when those studs have a death grip on the cast iron.  Luckily, I was able to get a few head gaskets last year from Then and Now Automotive and have them sitting on the shelf.

[39BuickEight]

"jumped time" is a word I hear many people use to describe virtually any reason a vehicle isn't running correctly

[billorn]

I havent seen it happen but I did have a 69 Caddy where the cam gear had teeth worn down to points and there was so much play in the chain that it acted like it jumped a tooth or 2. If you didnt have another gear to compare it to you might not see how worn it was because it was so even but when I got a new one it had square teeth not pointy and the wear was very visible.

[edinmass]

Possible? Yes.  Do a compression check. You sure you don't have any sticking a valves.  If you have no stuck valves,  and then low compression ,  consider the chain.  I agree with the above.  It's very unlikely but possible.  A blown head gasket between two cylinders would cause the same backfiring symptoms.  We also explain overheating.  Take your time and be methodical. 

[Guest]

If you have to pull the head, leave everything else on the engine, start it and run it for a minute, then loosen all the head nuts and start the engine again.  Usually juts firing once or twice will pop the head  loose. 

[capngrog]

I know nothing about a '28 Chandler, so take my advice "with a grain of salt".  I learned the hard ($) way that a bad vacuum leak or a severely lean carburetor can cause an engine to act like it's off time, dropped a valve etc.  I would check that out thoroughly before tearing into the engine.  As another thought, is it possible that something has gone amiss with your distributor?  Is it possible to perform all the usual checks, such as compression, on a '28 Chandler?  I would think that if the cam timing is off that the compression would be affected.

 

Just my guess.

 

Cheers,

Grog 

[keiser31]

Happened to my 1974 Plymouth Duster. I was going along, minding my own business when a guy ran into my quarter panel from a freeway offramp. The car was jolted so hard that the timing chain jumped.

[padgett]

Well GM from 1969 to 1972 used in some engines (SBC was one) a fiber timing gear that broke. I made sure when I ordered my 72 Wagon that it had a steel timing gear (400-2bbl didn't, 400-4 bbl did). Had to pull the front cover to see but was obvious if had jumped time.

[PFitz]

If the chain was loose enough to jump, you'd likely here is "hissing" as it rattles.

 

Does your 28 have a potmetal carb, or at least a potmetal venturi ?  With heat cycling and engine vibration a well running potmetal carb can go down hill quickly.  And they can fail either rich, or lean depending on where they develop internal cracks.  28 is right in the middle of the bad die cast era.

 

Paul

Edited May 17, 2017 by PFitz (see edit history)

[oily rag]

I have had it happen with worn timing chains. 

I also the gear on the bottom of the distributor split on a 1970 Plymouth 225 six cylinder. that really threw the timing off.

[Bhigdog]

Yup. 62 Pontiac. Jumped for no apparent reason....................Bob

[Guest]

Back in '74, I had a '72 Ranchero GT with a 351C. It had been running fine, and I was getting ready to go on a trip. Threw my bags in the back, and cranked it over - nothing but popping back through the carb occasionally - would not start although it had both spark and fuel. Confirmation of it having jumped time was that when number 1 cylinder was brought up to TDC, the distributor rotor was nowhere near to pointing at the number 1 position on the cap. Teardown revealed nylon ( or whatever the plastic like material was on the cam gear) broken off leaving small nubby teeth which the chain had jumped. I had shut it off not 30 minutes before. I suppose the torque of cranking it to start caused it to jump at that moment.

Edited May 17, 2017 by Guest (see edit history)

[Dave Young]

She did have the dreaded Schebler S-3 pot metal nightmare on it.   Now, she sports a 10 pound monster Zenith, all cast iron updraft and it made a world of difference in the drivability.  Lean on fuel was my first suspicion, as was the blown head gasket. Oddly, one plug is oil fouled.  The others are all very nicely colored.  The oil foul is a brand new change.  It's on number four.  One set of points in this distributed fires 4 of the cylinders and the other set of points fire the other 4.  I only did a compression check on the fouled hole, and got a respectable 50 lbs.  70 would be ideal.  I will test the remaining 7 before doing anything else at this point.  Thank you for the tip on popping the head.

[sfair]

Many times you can hear this problem when cranking with the starter.

It will have a different lope/cadence/crank faster than it did before.

[Dave Young]

Fitz,   The flex discs that you made for the driveshaft on this car are superb.  It totally eliminated the driveline vibration that seemed to be be shaking her apart.  Many thanks for a job well done! 

[PFitz]

12 minutes ago, wilbur said:

Fitz,   The flex discs that you made for the driveshaft on this car are superb.  It totally eliminated the driveline vibration that seemed to be be shaking her apart.  Many thanks for a job well done! 

 

Your very welcome, Dave. Glad to hear that's all it took to get rid of that vibration. 

 

 Like many other car and truck manufacturers, Chandler  knew that those flexible discs can absorb and dampen vibration and drive train sounds better than all-metal u-joints can.  Because of that natural dampening ability they are much more forgiving of less than perfect drive shaft balance. That's why many inboard engine boat builders and high-end European cars are still using flexible u-joints for propeller and drive shaft couplings.  

 

Paul 

[PFitz]

45 minutes ago, wilbur said:

She did have the dreaded Schebler S-3 pot metal nightmare on it.   Now, she sports a 10 pound monster Zenith, all cast iron updraft and it made a world of difference in the drivability.  Lean on fuel was my first suspicion, as was the blown head gasket. Oddly, one plug is oil fouled.  The others are all very nicely colored.  The oil foul is a brand new change.  It's on number four.  One set of points in this distributed fires 4 of the cylinders and the other set of points fire the other 4.  I only did a compression check on the fouled hole, and got a respectable 50 lbs.  70 would be ideal.  I will test the remaining 7 before doing anything else at this point.  Thank you for the tip on popping the head.

 Ok, pot metal can be crossed off the list.

 

Oil fouled plug ?  As Edinmass suggested, I'd do a compression test before pulling anything apart.

 

 Is the spark healthy to that plug  ?  How old are the spark wires ? Are they in a metal loom, as was common practice then ? Do you have a  timing light (poor man's oscilloscope) ? If so, even if it's only 12 volt timing light you can power it with a modern car and just use the pickup leads on the Chandler.

 

Clip the pickup on each plug wire in turn, point the light at a surface that will let it be easily seen and watch the flash sequence very carefully. Are the flashes steady and evenly spaced .... or does it skip a flash now and then ?

 

Are any of the wires showing a quick double flash ? If so that's cross-firing - either a short from the insulation breaking down (can happen with high heat not just a break in the insulation - topic for another thread), or inductive cross-firing caused by the magnetic field of the wires being so close inside the loom. If it happens at the right time it can cause some of what your experiencing.

 

Paul

 

 

Edited May 17, 2017 by PFitz (see edit history)

[Dave Young]

It does have the metal conduit that all 8 plug wires run thru and I did suspect a cross fire situation as a cause of the chuffing thru the carb.  So, rather than pull the wires out of the tube, I swapped out the entire assembly from my other Chandler, cap and all and she ran exactly the same.  I used one of those neon spark indicators to show fire, but I like the idea of the timing light as it would be much brighter and easier to see.  She definitely sounds different when cranking.  Very inconsistent.  In the moments before the change occurred I thought that the water pump was making a strange noise so I pulled over and cranked in on the pump's grease cup and motored on.  I barely made it home.

[JACK M]

Sometimes a coil going bad will cause those symptoms.

[benjamin j]

you said running hot was a symptom. firing at the wrong time like when exhaust vales are partially open will cause the heating up issue. loss of power means you have to give it more throttle than normal which in turn means more raw fuel into the exhaust. of course it could be the distributor moved of the timing chain jumped.  they are both fairly common issues.

[Dave Young]

I'll take a look at the coil too.  Thanks.

[Dave Young]

The first symptom was much more throttle needed to power the car.  Then came the cuffing out the carb.  This distributor drives off of the generator shaft, which is the only means of adjusting the timing chain tension.  It might be possible that the chain jumped a tooth on the generator and not on the cam, putting the ignition timing off and not affecting the valve timing.  The road ahead is getting pretty steep!

[benjamin j]

45 minutes ago, wilbur said:

The first symptom was much more throttle needed to power the car.  Then came the cuffing out the carb.  This distributor drives off of the generator shaft, which is the only means of adjusting the timing chain tension.  It might be possible that the chain jumped a tooth on the generator and not on the cam, putting the ignition timing off and not affecting the valve timing.  The road ahead is getting pretty steep!

ignition timing being off still means firing when valves are partial open.

[Dave Young]

Well, I just did the compression test.  Number 5 and number 8 are real low... and they are next to each other in firing order.  Most of the cylinders are making 80 pounds, but those two are down in the 30's.  I think I'm going to start loosening head bolts.  Once I get them all to move, I'll retighten them and run it a little bit.  Then remove the nuts from the studs and fire it up.  The fact that 5&8 are sequential in the firing order is pointing toward the "jumped chain" and away from the blown head gasket idea.  Damnit.  Chandlers were never meant to be worked on!  The removal of the timing cover entails removing the engine from the car.  Imagine if you needed to service the generator, which is part of the timing chain system, you need to pull the engine just to get the chain back onto the generator sprocket.

[edinmass]

It's not a timing chain, all of them would read the same if it were. Think burnt valve from running lean. If you put a probe in the cylinder of number one and bring it up to top dead center to be sure you are correct, pull the head without turning anything over. You will find burnt or stuck valves, or open valves when they should be closed. My bet is burnt exhaust valves. Good luck.

[PFitz]

I agree with Ed. Jumped timing would throw the compression off on all the cylinders, not just two out of eight and leave the other six cylinders right where they should be for a typical compression ratio of that era.

 

Paul

Edited May 17, 2017 by PFitz (see edit history)

[Dave Young]

I would be very happy to have to deal with valve problems and not have to mess with that chain.  The lean issue could certainly have come from me running a different carb than designed for this engine.  The plugs are lighter colored than I usually like to see.

[PFitz]

One way to further check is run compressed air into those two cylinders, (one at a time)while your certain that their valves are closed. Then listen at the carb and at the tail pipe for air hissing sounds.  If your compression gage hose won't hook up to air hose, take an old spark plug, knock the porcelain insulator out, thread the inside with pipe thread to thread a make quick disconnect fitting into it. Snap that onto a female quick disconnect on the air hose.

 

Try tapping the valve stem, or rocker arm end to get the valve to open then snap shut and listen again for change.  if the hissing stopped you have a sticking stem in it's guide. If it keeps hissing then a burned valve is most likely.

 

Paul

Edited May 17, 2017 by PFitz (see edit history)

[MikeC5]

You could see if a local mechanic has a good borescope to allow a peek in the combustion chambers (via spark plug hole) to look for signs of burnt valves.  Have you double checked valve adjustment?  Better to set them up a little loose so heat expansion won't keep a valve from closing completely.

[intimeold]

I just want to weigh in on the "Original Question",  Do "jumped timing chains really happen"?

 

When I worked as an automotive technician; we often heard about jumped chains.  I worked mostly on Ford, Mercury Lincoln products; but also all of the other makes.

 

Some engines use timing gears that mesh together; rather than a chain and a crankshaft sprocket and camshaft sprocket or camshaft sprockets, depending on how many camshafts.

 

Jumped timing happened almost always, in an engine that used gears rather that a chain and sprockets.  Mostly because the camshaft gear was made of some sort of reinforced fiber.  That fiber gear would have the teeth sheared off.  The reason for fiber cam gears is most for noise reduction.

 

I don't ever recall a camshaft chain slipping in the sprockets.  I did see very loose chains; that had to affect engine timing greatly.  The engine would still be in "time"; but very poor performance.

 

Jumped Time was one of those phrases that just stuck.

 

intimeold

[Marty Roth]

Agree with Edinmass -

 

but check for tracking on your distributor cap for arcing or crack (inside or out), or try your spare cap before opening the engine. 

The potential for Cross-Fire may begin there !

 

Yes, Timing Chains DO jump:

1954 Ford 6-Cylinder

1966 Pontiac (gift from friend in Richmond, VA - chain stretched so much that it "looped" over the upper gear and wore a hole in the front cover/water pump housing, allowing water into the oil.

1969 Tempest with the Pontiac (not Chevy) 350ci engine - chain "Jumped" at 80,xxx miles - Fiber Timing Gear was the cause.

 

Fiber gear was used as far back as the 'teens/'20s as a method of quieting the engine, compared to metal gear

[Dave Young]

Carbon tracking in the cap was one of my initial thoughts, but there were none.  Thank you, intimeold, for going back to my original question. It's something that I had always heard of, but never had anything of mine do it.  I manage about 50 pieces of heavy equipment such as cranes, forklifts and trucks everyday.  Granted those are modern iron and have timing gears, but still it makes one wonder.   Anyhow, I had checked the lifter clearance a few months ago while I had the manifolds off to address cracked flanges, bad gaskets and other issues.  They were all a respectable 10 thou, so I left them alone.  I later learned that Chandler liked them to be .007, so I just figured I'd do that next time I was in there.  Surprisingly, it has adjustable lifters.  

[Dave Young]

[JamesBulldogMiller55Buick]

12 hours ago, keiser31 said:

Happened to my 1974 Plymouth Duster. I was going along, minding my own business when a guy ran into my quarter panel from a freeway offramp. The car was jolted so hard that the timing chain jumped.

That happened to my Dad and his 1969 Grand Prix. the other guy was goiing the wrong way on a one way street. He T-boned dad's pontiac in an intersection

Edited May 18, 2017 by JamesBulldogMiller55Buick (see edit history)

[HuntzNSam]

The check I was taught – remove the distributor cap, grab the belts or put a breaker bar on the crank bolt, and rotate the engine backwards until the rotor just begins to move.  Rotate the engine forward until the rotor begins to move and roughly note the movement necessary.  Loose chain/blown gear jumps out like a wow!

 

3 times for me – 73 Chevy 400, 76 E250 351W, and 87 F150 300 (gears).  The first giveaway is running OK, shut it off, and won’t restart but is cranking really fast, like no compression.  

The Chevy, advancing the distributor got it running enough to get it a few blocks home to do the job in the garage.   Cam gear nylon wiped out, down to the metal core.

 

The father-in-laws E250 work van chose to die in my driveway, and no coaxing would get it to limp.  Too tall to fit in garage, and blocking my car inside, I did the job in the drive.  AC& PS bolted to the timing cover, and sub-zero temps, that job sucked.  I worked until my fingers froze, then warm up, and back out again, If you’ve ever done one, you know what I’m talking about.  Cam gear nylon wiped out, down to the metal core. (The AC never went back on).

 

The 300 six died in the drive (good truck!) and the rotor wasn’t rotating at all during the check.  Fiber cam gear wiped smooth.  Younger and optimistic, I assumed the cold oil change would drain all the shredded fiber.   Within a week, the oil pressure dropped ominously.  I just knew – dropped the pan and the oil pickup screen was jam packed with gear material.  Cleaned it out and all good.

[viv w]

A faulty ignition condensor can also cause the problems you are describing, I kept having the same faults on my Model A until I moved the condensor.

Viv.

[R Walling]

 I had a boat with a Gray marine engine in it and once it failed. It sounded like the timing was off so we took the dist. out and advanced it one tooth. It sounded like it would just start but no dice.

 

 We were floating down the river with 3 cases of beer so we weren't too concerned about getting the engine running.

 When the beer was gone. we checked the gear on the distributor and found that it had spun on the shaft.

 

By then we were close to the dock and were towed in. (but we enjoyed the ride though.

[Mike36]

3 cases of beer? How many guys were in that boat!?!?