What would cause breaking a timing chain or timing gear?

murse

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Sorry wasn't sure where to put this, but figured road side has a lot of traffic.

Last fall I upgraded to a Vortech V7 JT (forged motor) we were seeing valve float so I decided to do cams/springs. (Local shop has done all my work) Had comp cams/springs/retainers installed and retuned (made 607 rwhp) a week later coming home form work it started making a metal on metal sound and shut down. Towed it to the shop and found a broken secondary gear.

sec.jpg


Of course it bent some valves, so i had some head work done and had the spark plug threads upgraded to a 8 thread. We replaced the secondary gears with L&M billet gears and Ford performance camshaft kit ( m-6004-a464) So all new chains/tensioners/guides and the billet secondary gears.

Fast forward to last weekend, driving home from work, passed a slow car (i was in boost, but not upper rpm's) and car made a weird noise and smoked/puffed and was running rough. I pulled over, shut it off and when i climbed out of the car I saw oil trail behind the car. I lifted the hood and saw the driver side valve cover with a hole and the primary timing gear with no chain.

So how the hell do you break either a secondary gear or primary timing chain???? could it be bad springs???? Is my car cursed???
oil.jpg
hole.jpg
 

RedVenom48

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4.6 4v I'm assuming?

Springs could be too heavy for the crank gear. I believe the crank gear is a powder metal, while the primary gears are traditional metal. You could have broken the crank gear due to the increased load from the heavy springs and it spit out the timing chain for that bank.
 

7998

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Detonation possibly. Chain guide or tensioners could be worn and given way causing slack.
 

SecondhandSnake

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Going the FTA route, you first have either insufficient strength (material, metallurgy issue possibly), or stress higher than designed for. The stress higher than intended could come from all sorts of factors, including the heavy springs, or maybe some sort of torsional/harmonic stress. I know any sort of engine speed instability, like misfire or anything of the sort, can cause some incredible stresses on rotating components due to the rapid acceleration/deceleration of engine speed.
 

Relaxed Chaos

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It appears you are engineering through trial and error testing. The stress on components is higher than the strength of components. This design work is usually determined through rigorous engineering analysis, component design, and material selection, and then verified through rigorous life testing. You skipped all the engineering work, and went to right to endurance testing and are experiencing infant or useful life failures.

This is the risk you take on when you modify without proper up front work.

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murse

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4.6 4v I'm assuming?

Springs could be too heavy for the crank gear. I believe the crank gear is a powder metal, while the primary gears are traditional metal. You could have broken the crank gear due to the increased load from the heavy springs and it spit out the timing chain for that bank.

Yes 4.6 How many people have broken gears after swapping in a cam??

Detonation possibly. Chain guide or tensioners could be worn and given way causing slack.

I put brand new guides/tensioners/chains after it broke the 1st time.


It appears you are engineering through trial and error testing. The stress on components is higher than the strength of components. This design work is usually determined through rigorous engineering analysis, component design, and material selection, and then verified through rigorous life testing. You skipped all the engineering work, and went to right to endurance testing and are experiencing infant or useful life failures.

This is the risk you take on when you modify without proper up front work.

Squeezed out with help from the svtperformance.com mobile app

Skipped the engineering work???? How many people install new cams and springs with off the shelf kits and have problems???? I think most people don't have a problem. I upgraded the secondary gears with billet figuring that was the weak link, obviously not.
 

DSG2003Mach1

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I know we've got a couple engine building gurus around but I'll be damned if I can remember their names, hopefully they'll be able to give some insight.
 

svtfocus2cobra

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I've seen it happen on a 2015 Jeep Cherokee. Oil passage to the camshaft got blocked by a metal shaving from the previous failing camshaft, and so the cam seized and it snapped 2 of the 4 new gears on it.
 

RedVenom48

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Yes 4.6 How many people have broken gears after swapping in a cam??



I put brand new guides/tensioners/chains after it broke the 1st time.




Skipped the engineering work???? How many people install new cams and springs with off the shelf kits and have problems???? I think most people don't have a problem. I upgraded the secondary gears with billet figuring that was the weak link, obviously not.
Typically, the oil pump gears, crank gear and secondary gears are all powder forged metal. By upgrading the secondary gears, you made the crank gear the weak point.

I'm definitely not an expert, but if you used the factory lower gear, it wasn't mean for higher spring pressures.

Gotta get the timing cover off and see what happened.
 

murse

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Typically, the oil pump gears, crank gear and secondary gears are all powder forged metal. By upgrading the secondary gears, you made the crank gear the weak point.

I'm definitely not an expert, but if you used the factory lower gear, it wasn't mean for higher spring pressures.

Gotta get the timing cover off and see what happened.

That's next, and I agree the lower was left as a "stock" piece... my question is, Does everybody that does a cam, install all billet pieces??? how many people are breaking stuff????? I'll reach out to Todd Warren and see what he says.
 

01yellercobra

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What do the cams and cam journals look like? The only time I've seen breaks like that were either because the cam bolt wasn't sufficiently torqued and the gear worked loose or the cams were starved of oil and they siezed.
 

murse

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What do the cams and cam journals look like? The only time I've seen breaks like that were either because the cam bolt wasn't sufficiently torqued and the gear worked loose or the cams were starved of oil and they siezed.

I'll know in a few days when he gets a chance to pull it apart. My thoughts exactly the first time it broke.... like what the hell seized/locked up enough to snap a gear????

Does every one upgrade to all billet stuff when doing a cam/valve upgrade???
 

01yellercobra

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I'll know in a few days when he gets a chance to pull it apart. My thoughts exactly the first time it broke.... like what the hell seized/locked up enough to snap a gear????

Does every one upgrade to all billet stuff when doing a cam/valve upgrade???
Doesn't take much to snap something if the engine is already moving. Somethings gotta give.

I ran stock components in my old big bore set up. But then there weren't a lot of upgrades back then. Think about all the stock 03/04's making big power with stock stuff. I'm thinking you have an oiling issue and the cams and journals are going to show signs of that.
 
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Weather Man

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I had a built 3V with all new timing chains and guides. Decided to do a cam change shortly after and there was evidence the new guides had been deforming. Went with billet guides.
 

lOOKnGO

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This break is not uncommon. Take notice of the pic you provided. They seem to break at the keyway point on the gear. I purchased a lot of experimental 4.6 dohc testing hardware in Michigan in 05. Also left over racing hardware. I probably still have some perpritory cam designs that showed where the gear key broke and spun around the end of the cam. I questioned the race engine builder. He said the bolts are one time use only. Good luck.
 

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