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Old 02-14-2017, 02:57 PM   #1
wrldky
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Default Broken Cam Gear and Chain

Can anyone think of why the cam gear would break into 4 pieces and the chain would snap on a newly rebuilt engine? Camshaft and Crankshaft seem to be fine.
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Old 02-14-2017, 03:01 PM   #2
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Default Re: Broken Cam Gear and Chain

The non genuine 4.0 and 4.6 are piles of crap. Both the Bosch and GEMS had tons of run out that would surely do what you described. Got a picture of the upper gear? They look bad enough that it'll be easy to identify even in pieces


Unfortunately you now need valves and headgaskets along with a timing set
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Old 02-14-2017, 03:32 PM   #3
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Default Re: Broken Cam Gear and Chain

The chain and gear were less then a year old so I did not change them with the rebuild. I cannot recall where I bought them from but why would both break?
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Old 02-14-2017, 03:42 PM   #4
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Default Re: Broken Cam Gear and Chain

I was able to go back and search and I bought the parts from a very reputable guy in Virginia who does a lot of work on his own Rovers. I doubt very much that it was the parts and that would be too much of a coincidence.
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Old 02-14-2017, 03:43 PM   #5
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Default Re: Broken Cam Gear and Chain

Because the upper cam gear is eccentric in the crappy ones
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Old 02-14-2017, 03:46 PM   #6
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Default Re: Broken Cam Gear and Chain

Quote:
Originally Posted by wrldky View Post
I was able to go back and search and I bought the parts from a very reputable guy in Virginia who does a lot of work on his own Rovers. I doubt very much that it was the parts and that would be too much of a coincidence.
What brand?
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Old 02-14-2017, 05:06 PM   #7
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Default Re: Broken Cam Gear and Chain

Went and spoke with the guy who rebuilt the engine. He seemed to know immediately. He said that the engine back fired. He said it has happened to him only one but that was exactly what happened.
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Old 02-14-2017, 05:27 PM   #8
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Default Re: Broken Cam Gear and Chain

That guy is full of shit

It backfired after it failed and bent the valves. It was the reaction, not the cause

Since he's seen this before, that's a good indication that he doesn't know what he's doing
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Old 02-14-2017, 05:35 PM   #9
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Default Re: Broken Cam Gear and Chain

One likely led to the other, such as failing cam gear took out the chain.

That backfire explanation seems questionable. No matter how the engine is firing, there should not be significant torque on the camshaft - it just spins, bumps, does its thing. No real way to bind things up unless it's lacking lubrication. I'd put my bet on latent failure of the cam gear leading to desctruction of the timing chain. If you really wanted to be a detective, you could look for signs of old fractures on the cam gear pieces.
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Old 02-14-2017, 07:29 PM   #10
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Default Re: Broken Cam Gear and Chain

As mentioned, non-OEM cam gears are massive piles of shit.
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Old 02-15-2017, 12:42 PM   #11
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Default Re: Broken Cam Gear and Chain

Non OEM cam gears are junk. Robert and I built my 4.6 motor two years ago and used a non OEM cam gear. during the build. Just spinning the motor by hand you could see the cam gear moving up and down as it rotated and feel the difference in the tension on the timing chain. It would be good and tight half way through and then sloppy the other half. That junk went in the trash and a OEM one went on. That took care of all the issues, luckily this was caught during the build.
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Old 02-15-2017, 03:06 PM   #12
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Default Re: Broken Cam Gear and Chain

If you look at the inside of your front cover there is probably a piece broke out where he put a long water pump bolt in a short hole the chunk fell between the gear and the chain, usually only breaks the chain and of course all the bent valves
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Old 02-15-2017, 03:23 PM   #13
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Default Re: Broken Cam Gear and Chain

"Range Rover,"

Your response to my posting was actually my first thought. It being a new timing cover we mounted the water pump prior to reinstalling the timing cover. I asked my mechanic if this was possible and he said he didn't believe so. What are your thoughts?
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Old 02-15-2017, 10:44 PM   #14
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Default Re: Broken Cam Gear and Chain

Quote:
Originally Posted by roverover View Post
If you look at the inside of your front cover there is probably a piece broke out where he put a long water pump bolt in a short hole the chunk fell between the gear and the chain, usually only breaks the chain and of course all the bent valves

ive seen dozens put in the wrong hole and only the bolt worn into by the chain, literally like 2/3 of the tip worn off. never seen a genuine chain or cam break. No experience with aftermarket because I was at the dealer but if anything like the other aftermarket stuff I dealt with probaboly could break the chain or pulley.
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