Imperial Homepage -> Repair -> Engine -> Timing Chain
Question from Roger:
If a car is properly maintained "IMPERIAL" about how many miles should one drive before replacing timing chain?
Replies:
From Steve:
The only time I ever replaced a timing chain in a Chrysler product was my FIRST Chrysler product 15 years ago: A '69 NY'er when it got 165,000 miles on it. The 440 in it ran great but I felt like dumping $$$ in it. Good thing I did because the factory camshaft sprocket had half of it's nylon/plastic "teeth" missing. I installed a double-roller, steel timing chain/gear set. I replaced the cam and lifters too, but that was a waste because it showed NO wear at all. I guess MoPar figured the nylon/plastic "teeth"/aluminum sprocket would run quieter than a steel chain/gear set. Am I right??...anyone. It WAS quieter but I am not sure that was the reason why they went that route. Incidentally, the Holley carb/Edelbrock intake I used then is the same one that I use today on my '75 Imp....15 years later.
Reply from Pete:
Yes, you're right. The chain with an aluminum/nylon sprocket runs quieter than with a steel one. Toothed belts are even quieter, but have their own problems. Just ask somebody who doesn't replace the one in their F*rd Escort at the suggested 60k interval.
Reply from Mark:
Yep, nylon was used because it quieted down the timing gear noise. And, actually, the gear was aluminum, but with nylon bonded over the tooth area. I've never really cared for the double row chains, as they seem to stretch a fair amount. I understand you can get "pre-stretched" chains these days. I've found the best set-up to be the regular-style chain but with the full-steel gear. They come in various thickness (widths), the thickest (and longest-lasting) being the ones the factory used in the '63-'64 Max Wedges.
From Pete:
IMHO you're definitely pushing your luck after 100k. At 110k or so you're living on borrowed time. I'll email you a picture privately of the cam sprocket from a 69 440 with 110k on it (or what's left of the sprocket).
Question from Richard:
Having had enough of the way the thing was running and being fairly sure that the timing chain had so far outlived it's expected service life, I just spent the afternoon tearing down the front of my motor. With the front cover removed and the chain exposed, things looked better than I expected, aside from the lack of a front cover gasket. The chain is a double roller, not too badly stretched, and not showing a lot of wear on the gears. So on to the next step, rotate the engine around until the timing marks on the gear line up. Just for the hell of it I decided to pop the distributor cap off and guess what, the rotor is pointing at #6, not #1 !! Ok, check the books. Clean the crank gear until I'm sure I'm looking at the right mark. Check where the key ways on the crank and cam are. Pop the hood on one of the others and compare plug wire routing and distributor position. Everything was where it was supposed to be, except the rotor. With used cars, anything is possible, but why did this engine even run??? Ok, so it wasn't running that great, but it started easily, didn't backfire, and did a fairly good job of getting out of it's own way. I still say it shouldn't have run at all. Thoughts??
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From Jack:
Try 180 deg out assuming the firing order is 14836572, which it is for every American built engine except for Ford. Six would be the fifth cylinder fired or the first fired if the the distributor was installed 180 out. It will still run, but not that well. Done it on a Chevy. Ain't physics great!!
From Chris:
Sounds like an experience I once had (OK, caused), when I was 17 and working on my first car, a compact German sport coupe of a brand no longer sold in the US except to ducks... Anyway, I needed to rebuild my distributor to correct the excessive up-down play that was breaking my ignition points about once a week. (I bought points by the 10-pack from at the auto parts store where I worked, and before long I could replace them and static-time the car in less than two minutes on the side of any road.) Finally, I began the task, pulled the distributor, learned how to use an impact wrench (steel screws in an aluminum distributor casing), and re-built the distributor on a workbench. Easy enough so far. When I went to install it, however, I could not get the gear at the bottom of the distributor to sit into the mating gear in the engine (it also ran the oil pump in this car). Try as I might, it wouldn't go. I twisted, I pushed, I cursed and cried. I called my boss, a former mechanic who was patient with me more than he needed to be. Even he couldn't get the thing to seat. We ended up installing the distributor 180 degrees from normal and re-routing the wires. It caused no problem in drivability because as long as the cylinders fire at the right part of the crank's rotation, the car didn't care which way the vacuum advance pointed. It only needed to send spark in the right order to the right plug. I always set the timing by seat of pants anyway... I'd keep advancing it until I heard pinging, then backed it off a little more than I thought I should (since the earliest detonation can be inaudible). So I didn't care where the timing mark on the flywheel was, relative to the distributor. I'd bet that once upon a time someone had the distributor out and installed it 90 degrees off (if #6 and #1 are two cylinders apart in the firing order) or 180 degrees off (if they're four cylinders apart in the firing order... you'd think I'd have memorized my firing order by now, no?). Or, more likely since you say the outside of the distributor look the same, perhaps they reassembled the distributor with the cam out of orientation in the same way. But as long as they could get the timing close to correct and the plug wires sorted, there's no reason the car wouldn't run this way. You could leave it this way or set it right so you feel better, but the car will probably run about the same. Maybe if you feel like taking the distributor out it would be a good time to convert it to electronic ignition with a Mopar conversion kit...
From Kne:
I'm not sure if there were factory steel sets or not. Most of the ones I pull from old engines have steel chains (non-roller) and nylon teeth. Some replacement non-roller sets are steel sprockets, but steel non-roller chain. Yes Brand X is/was always notorious for nylon gears that self-destructed, as they were totally nylon I believe, the Mopar sprockets had a steel base or center, with nylon teeth, as you will see, which makes them a bit more reliable/stronger. Most likely when a Mopar set gets to the point of cracking and losing teeth is when the brand X unit would totally fail. It's amazing to me that they did this for a more "quiet" engine, as I cannot tell a nylon set from a steel set just by listening to the engine.
Question from Bruce (440):
Re: the mighty '78 NYB with it's 400 ci engine. I'm ready to re-install the timing chain cover, but have a question about the seal for anyone who has actually done this.
The timing chain cover is a stamped piece of steel. Where the seal goes there seems to be circular pressed piece of steel with a lip at the bottom, creating a (approx) 1/16" channel between the pressed-in piece and the stamped timing chain cover. This pressed-in piece appears the same metal and thickness as the timining chain cover itself, which made me think that it was a part of the cover. When I removed the old fossilized seal, the rubber part came out of this circular metal piece relatively easily, making me think the seal was just the rubber that came out. HOWEVER, the new seal from the kit (that the parts guy says goes on many other Mopars) has the same outside diamter as the outside diameter of the circular pressed-in piece. To use it , I would have to pull out the circular piece, which is in so snugly that I am afraid of distorting the timing chain cover. At least I will surely destroying the circular piece.
Does anyone know if this is what I need to do?
Reply from Steve:
The metal ring that is left in your timing cover is indeed part of the crankshaft seal and must be removed in order to replace the seal. I usually take an old screwdriver and drive the seal out from the front. It does fit tight and has the be driven back in place.
Question from Rich (440):
I have a '73 Imperial LeBaron, and when I had the timing set by specs the car ran bad. I took it to a good mechanic who set the timing by ear. He told me that he thinks the timing chain needs to be replaced. The car has 65,000 miles on it, and I thought timing chains should last until about 100,000 miles. Could this be possible that the chain needs replacement with only 65,000 miles?
Replies:
From Pete:
The real problem COULD be that the harmonic balancer outer ring has shifted on the inner hub. You can see if that happened by removing spark plug number 1, inserting a wire in the hole, and rotating the crankshaft to find the top of the stroke. Then look at the timing marks.
In my opinion, chain "stretch" is extremely unlikely to be a problem at only 65,000 miles. I've installed more than a few timing chains and they do stretch a bit after installation, but then they stabilize. You can verify that excessive chain stretch exists by following some simple procedures that your mechanic should already know. There's no guessing involved.
Much more common is deterioration/wear of the nylon teeth that are molded to the aluminum sprocket that drives the camshaft. Designed to reduce noise, the nylon/aluminum sprocket is the "Achilles heel" of the cam drive system.
While a newly manufactured timing set may last 100k miles, our cars are 30 years old and the nylon IS affected by exposure to oil and heat. It becomes brittle, cracks and then chunks of the nylon break off and fall into the engine sump. Check your drain oil for this, but it's much more likely that the chunks are sucked into the oil pickup (where they restrict oil flow). With part of the sprocket missing, the nylon shedding process accelerates rapidly and the chain becomes very loose. Then the chain rides on the aluminum nubs that are part of the sprocket casting. That lasts for a few days of operation and then the chain jumps, usually when you try to start the engine.
Here's a pic of the cam sprocket from a '69 440 having 110k miles. This car got to the "it won't start" stage.
From Steve:
Also you might want to check the vacume advance on your distributor and the lines running up to it.
Question from Richard (440):
I have a '73 Imperial LeBaron, and when I had the timing set by specs the car ran bad. I took it to a good mechanic who set the timing by ear. He told me that he thinks the timing chain needs to be replaced. The car has 65,000 miles on it, and I thought timing chains should last until about 100,000 miles. Could this be possible that the chain needs replacement with only 65,000 miles?
Replies:
From Peter:
As others have said, the real problem COULD be that the harmonic balancer outer ring has shifted on the inner hub. You can see if that happened by removing spark plug number 1, inserting a wire in the hole, and rotating the crankshaft to find the top of the stroke. Then look at the timing marks.
In my opinion, chain "stretch" is extremely unlikely to be a problem at only 65,000 miles. I've installed more than a few timing chains and they do stretch a bit after installation, but then they stabilize. You can verify that excessive chain stretch exists by following some simple procedures that your mechanic should already know. There's no guessing involved.
Much more common is deterioration/wear of the nylon teeth that are molded to the aluminum sprocket that drives the camshaft. Designed to reduce noise, the nylon/aluminum sprocket is the "Achilles heel" of the cam drive system.
While a newly manufactured timing set may last 100k miles, our cars are 30 years old and the nylon IS affected by exposure to oil and heat. It becomes brittle, cracks and then chunks of the nylon break off and fall into the engine sump. Check your drain oil for this, but it's much more likely that the chunks are sucked into the oil pickup (where they restrict oil flow). With part of the sprocket missing, the nylon shedding process accelerates rapidly and the chain becomes very loose. Then the chain rides on the aluminum nubs that are part of the sprocket casting. That lasts for a few days of operation and then the chain jumps, usually when you try to start the engine.
From Steve:
Also you might want to check the vacuum advance on your distributor and the lines running up to it.
Question from Rich (440):
I have a '73 Imperial LeBaron, and when I had the timing set by specs the car ran bad. I took it to a good mechanic who set the timing by ear. He told me that he thinks the timing chain needs to be replaced. The car has 65,000 miles on it, and I thought timing chains should last until about 100,000 miles. Could this be possible that the chain needs replacement with only 65,000 miles?
Replies:
From Ron:
I have seen Chrysler timing chains go before 50K and also last to 200K+ Many factors determine component life. There also exists another possible situation here, if after setting the timing "by ear" the engine runs/car drives normally, then most likely the timing chain set is fine, but the harmonic balancer has deteriorated and "slipped". Since the timing marks are on the outside dampener member, if the rubber cushion/joint between the inner and outer pieces fails then the outer member with the marks will become inaccurate as to TDC and ignition timing set.
From Rolland:
Timing chains should last 100,000 miles or more. without needing replacement. However, problems with the chain oiling system could cause premature failure but this is rare. If the mark jumps around and is unstable when the timing light is directed on the pulley it could indicate a loose chair. If it is steady and if the engine runs good after setting the ignition timing by ear I would suspect something else. The marks could have been placed wrong. Have you been successful in setting the timing to specs before? It could be the vibration damper has slipped a bit on the crankshaft pulley. I would check these things before replacing the chain. You can locate "Top dead center" by feeling the location of the top of the piston with a wire through the spark plug hole. It is difficult to get a 100% accurate reading this way but it should be close enough to tell you if the timing mark is off.
From Paul:
I don't know how much you plan on using your car, but if it runs fine, I wouldn't worry to much about the timing marks not being right. Since the gasoline that we now have is so inferior to what our cars are suppose to have, the timing almost has to be changed from the factory specs to run on our unleaded, low octane fuel anyway.
I have timed all of my Imperials by ear for several years now. That way I get the best performance with the least (if any) amount of spark knock. I always set the plug and point gap to spec, and then adjust the timing by ear. Some mechanics will tell you that is the best way to do it anyway.
The timing chain can get pretty loose before it will hurt anything. The worst thing it would do is rattle against the inside of the cover, wearing a hole through it and lose oil. Another thing it can do is skip if the engine runs backwards after you turn of the key from a condition known as "dieseling". Some American cars from the early 1980's did that from the factory.
From Elijah:
These symptoms sound more like a fuel delivery issue. Perhaps your carburetor needs attention, or there may be a vacuum leak somewhere.
From John:
Vacuum leaks is also something you should check for.
From Steve:
Have you done anything with the carb? My 72 would do this and I found out that the manifold to carb gasket was cracked. It was very pronounced when the engine was cold and would still do it although not as bad when the engine was warm.
From Matt:
I would try running the car on unleaded with no additive. I think Imperials began unleaded in 75 as I remember my grandparents neighbor getting a 74 NY'er as this was the last regular gas car according to him.
Question from Mark (440):
What is the life expectancy of a timing chain in a '68 440? I know it depends on a lot of factors, but roughly how many miles do you normally get? Are replacement timing chains for these cars hard to find? Are they metal? (I presume) What do you look for in order to determine if they need replacement? Reason I ask is, my car is running great - doesn't seem to have a timing problem - but I was going to replace the front seal because it's leaking and have been told I might as well go ahead and replace the timing chain at that point, since I'll have the front cover off. My feeling is, don't fix it if it ain't broke. I should be able to get several more years out of it, I would guess (67,000 miles on engine). ???
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From Richard:
My usual response is "replace it every 100,000 miles, whether it needs it or not" Replacements are generally metal, though the OEM nylon coated ones could be found. Avoid them.
> What do you look for in order to determine if they need replacement?
At idle, w/ the vacuum to the distributor disconnected, point a timing light at the timing marks. If you see the marks wonder around, the chain is generally toast. This assumes your engine is otherwise healthy and idles fairly steady. Another way to check for slop is to take the dist cap off and rotate the engine by hand. Removing the spark plugs makes this a lot easier. Spin the engine one way to take all the slack out, then spin it the opposite direction and not how far the crank rotates before the dist. rotor moves. Repeat as needed. With both methods, having another car or two handy for comparison helps.
> Reason I ask is, my car is running great - doesn't seem to have a timing problem - but I was going to replace the front seal because it's leaking and have been told I might as well go ahead and replace the timing chain at that point, since I'll have the front cover off.
It would really have to be a bad leak to warrant taking the front cover off just to fix it, and yes, as long as you've got the can of worms open, swap the timing chain.
Question from Terry (440):
Well this morning I started the project of replacing the timing chain on the 1974 Blue Imperial. I removed the usual suspects, water pump, folded back the A/C compressor, removed fan, radiator shroud, etc, etc... Now I am down to the Harmonic Balancer... The nicely sized 1 1/4 bolt seems pretty much planning on staying put in the balancer, and I don't know how to keep the balancer from turning so I can break the bolt loose. I have also removed the pulleys from the front of the balancer. Any ideas? BTW when I turn the engine one way and then the other, you can hear the timing chain clink and move in a way that I would think it should not. This only confirms my suspicion that the nylon gear has lost teeth.
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From Dick:
Easiest way is to borrow someone's 1/2 drive air Impact wrench, it will break the bolt loose easily, without moving anything else. Don't use it for tightening the bolt, however, use a manual torque wrench, and lots of muscle! (Look up the spec, probably at least 150 ft lbs.) You will have to clamp the flywheel with a Vise grip to keep it from turning when you reinstall the pulley.
From Richard:
Ah, yes, the joy of a timing chain-ectomy. You didn't mention the nasty little bolt on the water pump housing that hides behind a heater hose fitting, so I'll assume you dealt w/ that. As to the vibration damper, been there: Many will suggest using a tire iron or similar to jam the flywheel in place thereby keeping the crank from rotating while your trying to find enough torque to get that bolt off the front. My technique is to use a short ratchet extension placed in one of the holes along the edge of the damper. When you end up rotating the crank/damper w/ the socket, eventually the extension will wedge against something and hold the damper in place. You'll need to retighten the bolt and back off the damper to get the extension back, but it works. Remove the spark plugs to make spinning the engine easier! In an effort to make sure the timing marks on the new gear/chain set line up, I like to rotate the crank back to TDC before pulling the old chain off. After the damper and cover is off, the damper bolt works great for this, but make sure you thread a nut onto first or you'll have a hell of a time getting the bolt back off! Use the extension to jam the damper the other way when you put it back together.
From Kerry:
Mine came off with an impact wrench but it was out of the car. Short of wedging something to keep the crank from turning, I don't know any other way. You might try wedging a large screwdriver in the starter teeth on the converter but you might break one. I have also put a piece of 2X4 between the crank and the block but that requires you drop the pan first.
From Jorge:
When I replaced the timing chain on my 440 (and others ) what I did was to get a 1/2" ratchet with a socket on the big bolt (after all the others have been removed) slip a piece of pipe over the ratchet handle and put it in such a way that as the engine turns ( by cranking it with the starter motor) it loosens the bolt. No fuss no mess and quick.
From Ron:
If you don't have access to an Air Impact wrench or Air Compressor the job becomes quite tedious. As much as I don't like doing it, sometimes its the only way. In the past, I have left the belts and pulleys on so as to be able to wedge a 3/8" extension between the crankshaft pulleys and belts. As you try to loosen the center bolt, the belts tighten against the extension and keep the crankshaft from turning. Service books tell you to wedge against the flywheel teeth, but that is really difficult unless you have several pairs of hands.
Follow-up from Bob:
I had the same problem long ago trying to get the front pulley off an Alfa to replace a seal - vise grips broke the edge of the pulley! I rented/borrowed an electric impact wrench - it did the job.
From David:
Two options come to mind. The first is an impact wrench . If you don't have air then how about an electric impact (this is how I removed mine)? You might borrow, rent, ... The second thought is to put the pulley back on and use the belts to hold things still. That would have been more easily done before you removed all the accessories but I think it will still work.
From Kne:
I get out me old trusty vice grips, clamp them on the balancer and let them jam up against the water pump or whatever when I start turning the nut. I can hear someone shouting that that may shift the outer ring but it's never happened to me. Put a mark on it first if that does concern you. The other choice would be to pull the inspection cover off the bell-housing and jam up the torque converter/flywheel. Yes indeedie if you can hear the chain slopping around (and that is what you are hearing) it is way past time to replace it with real steel sprockets and a roller chain.
Follow-up from Terry:
Put large C clamp on harmonic balancer pulley. turned bolt till it hit, bolt came right out, no problem! Removed Harmonic balancer with Puller. Removed Timing chain cover BLECH, Timing gear was TERRIBLE almost ALL the nylon teeth where gone. how on EARTH could this car run AT ALL?? Answer: it didn't! :) Old chain had so much slop i took a picture for later posting on my website! New gear and chain went right in like a charm, tight and snug! Scraped off old gaskets and put new ones on. Closed timing cover put on Harmonic Balancer. QUIT... now it is 10:00 AM and 95 degrees and heading to 105! Next weekend, i will put the car back together and try to. start it.
Question from Bruce (440):
I am finally starting the much-delayed replacement of the timing chain on my '78 NYB. Brad Hogg graciously sent me the relevant service manual, which brought a new question. Is it necessary to be sure to NOT move the engine once the old chain is off? Also, the manual makes a big issue about using a strange tool to prevent the cam shaft from contacting the welch plug. Can anyone tell me what this is about, and what method I should use in place of the strange "C-3509" tool, which of course I don't have.
Replies:
From John:
You may be able to get that tool from Miller Special Tools. That is the company that originally made these for Chrysler. They are still in business & many of the widely used tools are still available from them. Not sure if their address in in the resources section or not.
From Frank:
It is not always necessary to have the special tools for some jobs. It is helpful but not always needed. If it is a camshaft holding tool and by the sound of your note, it would be to keep the cam from moving backward in the engine and knocking out the rear plug. This can be avoided by not banging on the cam gear with a hammer. Gears can be test fit without the chain to make sure they fit. You can turn the engine by hand if need be without doing any harm. By hand your not turning fast enough to bend valves. If your car has not jumped time you can take it apart then line it up, before you even remove the chain and gears.
Question from Kerry (440):
How much slack should there be in the timing chain on a 440. The one I'm rebuilding has a double roller chain on steel gears. I assume that someone had already changed it from the plastic gears everyone was talking about earlier. Or perhaps the truck engines came with steel gears. At any rate, how much slack should there be?
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From Richard:
The FSM is downstairs, but as I recall the factory recommendation: if you can move the cam gear more than 1/4 inch before taking up the slack, change it. My recommendation: check the gear teeth and chain for wear marks.
From Gary:
If your rebuilding the motor, why not spend a couple extra bucks and install a new timing chain and gears? I would recommend using a double roller again. No need to mess with it then
From Kne:
KNE's timing chain recommendation: For $30 or less, if it's already out of the engine........replace it! Even if it was within specs, what if it only had 1,000 miles left on it?
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