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Engine timing chain is broken


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Last weekend my engine went off after I was starting to go for a ride with my Mustang and was just about to leave my town. It sounded like backfire, but the engine went off and did not start again. Sound was normal when I turned the key, just the ignition seemed to be missing.

 

First finding from my garage was, the point set in the distributor was broken. So they replaced it, but called back the next day and told me crankshaft doesn't move and it seems the engine timing chain is broken. Now the engine needs to be disassembled to check what has been damaged inside

 

Since that would cost a fortune in that mustang specialized garage, I am planning to do that with a friend of mine who is a mechanic...

 

Now I thought if the engine (351C 2V) is anyway disassembled it makes sense to do a proper rebuild and replace some of the old parts before they break next spring as well. Any recommendations for a engine rebuild kit, specific spare parts or even nice and useful improvements?

 

So far I already changed the intake manifold and carburetor to Edelbrock parts (600cfm)

 

Thanks from Germany

Andreas

 

2n0srck.jpg

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A cam is always a good power adding option. If you keep it 'mild' you won't have to do a bunch of other upgrades.

 

But first let's find out what is wrong with the engine. It won't be hard to get to the timing chain. You pull off the front accessories, the water pump and the cover.

 

If you broke the timing chain you will want to remove the valve covers and take a look. It is possible some of the valves hit the pistions. The most likely scenario is it bent the push rods. But if you find the timing chain broken you will want to pull the heads to inspect for damage to the valves and the pistons. A worse case scenario is a piston twisted enough to break the block. Very unlikely. You will most likely find fluid in the cyl if this is the case.

 

These is something strang with the story. If the timing chain was broken how did they determine the points were broken? And you mentioned you were able to crank the engine but the shop now says the crank won't move.

 

As far as parts for a rebuild. What kind of performance are you looking to get from the engine? How much do you drive it? What kind of driving do you do? Also, what tranmission and rear end gears do you have? Do you have a budget in mind?

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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your engine does NOT have to come apart yet.

 

put a new chain on it then do a compression test . if it is good, the valves did not hit the pistons so you are good . if it bent a valve, you can probably just pull the head with the bent valve and fix it.

 

strange that this high end" shop didn't know this and tell you.

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I'm not sure why or how a broken timing chain also broke the points. One thing for sure, the broken points wouldn't function. I would verify that the engine does not turn over, and if it does watch the rotor while turning the engine over.

 

Start with the easy, external checks first. I would pull the distributor before I removed the water pump and cover plate, make sure the distributor gear isn't the problem.

 

If the engine won't turn it may be a valve head bent enough or broken and is stopping a piston. You'll have to a least pull the heads if it won't turn over (crankshaft doesn't rotate).

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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the first thing to remember is if the chain did break then turning the engine is not a good idea.. pull the rocker and push rods.. that way all valves hopefully are closed, unless one is bent.. turning an engine with broken chain changes the mechanical timing and u could be asking for trouble and more $$$$$$$$

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And, those chains are not an item that usually breaks as far as I know.

Broken/sheared teeth on the top gear, yes. Broken chain, not common.

 

Either way, like the others said, just diagnose the real problem first.

Pete - MotoArts Decals and Signs

'71 Sportsroof 351C-4V/4-speed - FINALLY under construction - no, wait, on hold again...

'90 Mustang 7-Up 5.0 ragtop, rolling beater - SOLD

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The attached picture is of a piston out of a Ford 302. My crazy sister borrowed the car from my dad. The timing chain had enough slack that it jumped time did not break chain. Her husband loosened the distributor and kept cranking the engine until it locked up from the valve breaking and sticking into the piston. It also destroyed the block & head. This was done while cranking not running. You will for sure have bent valves if it did jump time and if engine will not turn a broken valve and a piston similar to the one in the picture. There are a few Ford engines that are not interference engines the old inline 4 not the SVO version but the normal carb. would not hit the valves when it broke the belt on the OHC. I do believe they had to hit in your engine.

Hope the damage is minimal heads off first if engine will not turn before you damage it more.

When a man is in the woods and talks and no women are there is he still wrong??:P

David

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Because the timing chain broke, if it did, while driving down the road all of the internal damage has already taken place. Chances are there's more than one piston that looks like David's.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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I'm skeptical about the diagnosis. I'd get another opinion. I think that you would have some really rough engine operations prior to the failure. If anything would be turning, it would be the crankshaft. The cam and distributor would be still be if the chain was broken.

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I had a similar problem on the road w/ backfiring and dying and turned out to be a broken distributor gear which kept the engine from turning. pull the distributor and have it checked . you could turn the crank over by hand just a few degrees and if the dist rotor is not turning the chain ( or cam) is toast. If the rotor is turning when rotating crank by hand the chain should be good but maybe loose and jumped a tooth on the gear. turning crank by hand will not generate enough power to damage valves or pistons but cranking with the starter will cause damage.

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If you truly have a broken timing chain, the engine will have a very different sound when it cranks. It should sound like it's spinning much faster than usual...most of the time it will have the steady sound of gears meshing with 1 or 2 periods where it will slow down due to compression. This sort of pattern will repeat.

 

When we would get calls for, what turned out to be a broken timing belt, you could tell instantly by cranking the engine over.

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Hi all,

 

Thanks a lot for the great comments and hints. Will let you know what's wrong once we have time to look at the car in a couple of weeks. Will check the distributor and compression first...

 

Thanks

Andreas

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Hi all,

 

Thanks a lot for the great comments and hints. Will let you know what's wrong once we have time to look at the car in a couple of weeks. Will check the distributor and compression first...

 

Thanks

Andreas

 

Don't crank the engine over with the starter if it is jumped you might break a valve. Simple turn the crank with socket to TDC pull the valve cover and see where the valves are. If not in time you need to start pulling it down. Just cranking the engine over bends the valves at least. You hear the horror stories of the two piece factory valves breaking but that is only due to floating the valves or jumping timing. I have never seen one break without one or the other.

When a man is in the woods and talks and no women are there is he still wrong??:P

David

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Simple turn the crank with socket to TDC pull the valve cover and see where the valves are.

 

Agreed. First order of business is to verify what the "specialty shop" has claimed (and that the timing chain has indeed jumped).

 

Better yet, when you turn the crank by hand, simply pop the distributor cap and see if it's spinning on the cam. If it does spin, chances are your timing chain hasn't split in two (and you can breath just a teeny bit easier).

 

-Kurt

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How to buy a '71-73 Mustang:

Rule #1: Assume all classic car sellers are guilty until proven innocent.

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It doesn't spin, that's how they started to conclude the chain is broken once they replaced the damaged point set and wondered why it's not starting.. But I don't know if they pulled the distributor to check e.g if the distributor itself broke...

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If you're in luck, it will only be the cross pin that holds the drive gear in place....but if it is the cross pin, you need to look further to make sure you don't have another issue. I've seen where the oil pump locked up, broke the drive rod, and shattered the rotor. The owner replaced the rotor, fired it up and smoked the rod & main bearings because the oil pump was locked up.

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As others have said it is not uncommon for the distributor gear roll pin to shear stopping the engine dead.

 

Since you don't know what is going on, I would pop the distributor cap off and remove the passenger side valve cover. I would turn the crank with a socket and ratchet and verify that both the cam and distributor are both rotating with the crankshaft. You can also verify your timing now as it is possible for the timing chain to wear enough to 'jump' which is when it skips a tooth on either the cam or crank gear changing the relationship of the two. Jumping time could cause the engine to shut off as well.

Matt

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I have never seen a broken chain but gears worn and chain stretched to jump or the nylon gear that breaks on 302. I have fixed several with locked up oil pump caused by the rubber pieces from the valve stem guides. Can lock the bypass valve and blow the filters or lock up and break the drive shaft from distributor. There are all kind of gremlins out there.

When a man is in the woods and talks and no women are there is he still wrong??:P

David

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  • 3 weeks later...

so, finally we had the chance to take a first look at the engine. And in fact, the timing chain is broken. :(

 

will pull the engine out of the car in a couple of weeks and then looking further what happened to the pistons and valves.

 

Thought about replacing the cylinder heads with Edelbrock Performer RPM Complete Cylinder Heads as well the matching Edelbrock cam or a Comp Cams kit. Probably also getting a Federal Mogul rebuild kit with forged pistons etc. if the engine is anyway open.

 

Does anyone know if I have to swap my current Edelbrock Intake Manifold for the Performer RPM?

 

I don't want to make a race engine. just want to have a reliable, strong engine for the street...

 

But after today, it seems christmas won't have a lot of presents for rest of the family this year...

 

30ixjiw.jpg

 

9pxafo.jpg

 

2n0pie9.jpg

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so, finally we had the chance to take a first look at the engine. And in fact, the timing chain is broken. :(

 

will pull the engine out of the car in a couple of weeks and then looking further what happened to the pistons and valves.

 

Thought about replacing the cylinder heads with Edelbrock Performer RPM Complete Cylinder Heads as well the matching Edelbrock cam or a Comp Cams kit. Probably also getting a Federal Mogul rebuild kit with forged pistons etc. if the engine is anyway open.

 

Does anyone know if I have to swap my current Edelbrock Intake Manifold for the Performer RPM?

 

I don't want to make a race engine. just want to have a reliable, strong engine for the street...

 

But after today, it seems christmas won't have a lot of presents for rest of the family this year...

 

30ixjiw.jpg

 

9pxafo.jpg

 

2n0pie9.jpg

 

Now that's something you don't see every day.

 

Does the engine rotate?

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.

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Now that's something you don't see every day.

 

Does the engine rotate?

 

If you mean the crank shaft? Yes it was turning.

 

It looks like the harmonic balancer broke and took out the timing chain or is it the other way around?

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.

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Wow! I've seen broken balancers, but never a broken timing chain! Along those lines, I've seen the nylon teeth break off of the cam sprocket and jump teeth....many a timing belt stripped, but this is a new one.

 

I suspect you have more going on inside the engine (but I hope not). Please do keep us posted...I think there is some learning in this for us. Thanks for the update, by the way.

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All these members are spot on.. Seems the shop cannot pinpoint the issue due to a lack of experience with these 40+ year old engines. You stated the engine would crank over but not start, so that's an indication the crankshaft will rotate. Broken points don't make sense to me.. Never seen it happen..

An easy diagnosis is to crank the engine over by hand with a socket and ratchet on the harmonic balancer bolt with the distributor cap off.. If the rotor is turning, then the chain is still in place.. The cause of this problem might lay elsewhere..

The person who says it cannot be done should not interrupt the person doing it. 

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All these members are spot on.. Seems the shop cannot pinpoint the issue due to a lack of experience with these 40+ year old engines. You stated the engine would crank over but not start, so that's an indication the crankshaft will rotate. Broken points don't make sense to me.. Never seen it happen..

 

Hi piper62,

 

Actually the shop was right. The the chain is broken and the balancer got damaged as well. I've posted pics from the weekend when we opened the engine. Maybe the points got dmaged afterwards when I tried to start the engine a couple of times...

 

Thanks

Andreas

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