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Discussion Starter #1
If anyone out there has experienced a sheared distributor gear maybe you can answer this question? Does the rotor now spin freely or does it remain fixed? Since , when I turn my bottom end the rotor doesn't budge it would be good to know what the reaction of a broken distributor shaft to cam would be. I'm thinking that my chain must have somehow came away from the gears and that the rotor isnt turning because there is no connection between the crank and cam. I've also been told that corvette used plastic timing gears and that may be the reason for a chain that usually wouldn't come off to do just that. Any answers?
 

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A sheared dist gear can be caused by a few different things. But usually something has gotten sucked up into the oil pump and locked it up. This instantly shears the drive pin or ejects the distributor straight up! I have experienced both. My dragster oil pump once injested a tiny piece of wire brush hair and ejected the distributor from the car!!

Early GM motors had Nylon plastic coated timing gears that were famous for deteriorating, falling into the oil pan and getting into the pump. Instant shear pin in the dist gear.
 

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sheared gear

Unless your shaft is jammed, your distributor shaft wont turn with the camshaft and you should be able to turn it freely with your hand.

I dont recommend turning this engine over, as parts from the gear, or the lower distributor shaft, could cause further damage to the engine, not to mention your oil pump is driven by the distributor as well.
 

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Discussion Starter #4
So what you're saying is, if my distributor isn't jammed then the reason it isn't turning is because it's still geared to the cam and the problem has to be the cam to crank connection... the timing chain?
 

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sheared gear

The only way to know for sure is to tear it open, and inspect it. There are in truth many variables.
Your oil pump could be locked up, distributor gear broken and jammed. If it was your timing chain, you would probably have a difficult time turning the distributor anyway as you would also be fighting the springs in the valve train. One way to check for a broken timing chain is to take the top off the distributor and slowly turn your crank shaft. If the distributor doest turn, then its one of two things; timing chain or distributor gear/shaft.
 

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sheared gear

to eliminate the timing chain or gears from being the culprit, take off a rocker cover and see if the valves operate.
 

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I would pull distributor and check the pin .Also use a large screwdriver and try to turn oil pump drive.Sounds like oil pump locked up and sheared the pin .
 

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Discussion Starter #11
Okay, well, i'll take all this info and apply it tommorow. I'll come back to this thread and fill you guy's in on exactly what it was in case anyone is curious.
 

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Discussion Starter #13
:sweat: O.K. guys, here's the deal. I didn't have time to do much today because the car is at my work and it's hard to work on it while on the clock. Basically, i'm down to the a/c compressor. After that i'll be able to get to the water pump and then the timing cover. More important, i did have time to check the valve train while turning the crank and it doesn't move. I turned it over 4 complete times just to make sure. I can hear the chain dragging in the cover while i turn it over. (By hand only) I'm pretty sure that the plastic cam gear sheared some teeth and the chain fell off. Considering that my car has 170,000 miles on it, I wouldn't doubt it. Besides, I loved to launch the car hard and that probably helped it along. So as it stands I'm pretty happy that its only the chain. We'll see when i get the timing cover off how happy I am then. I'll keep you informed until the end. Thanks. Rick
 

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Discussion Starter #16
I will. It probably won't be until Saturday when i'm finished. Let me say that i'm very impressed that you guys go out of your way to come back to an old thread and continue to moniter and help. I intend to keep an eye open for your user names and offer any help i can. Rick:thumbup:
 

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Discussion Starter #17
Timing gears were stripped

Alright guys, heres what i found. The timing gears were stripped. Half the teeth were missing from each pulley. To make matters worse, when i pulled off the valve covers i found that 4 of my push rods were bent. They weren't bent very much as i could still pull them out. I'm pretty sure that they didn't bend when the car shut down because it went off quietly like i shut the key. I think they might have bent when i was cranking the engine over trying to start it. So, without going into removing the intake manifold and all that entails, ( it's a 350 tuned port injection) to check the lifters, what do you think the chances are the lifters weren't damaged ?
 

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Discussion Starter #19
your telling me that there's no way that the valves and lifters could be undamaged? Even if the engine was only cranked and not run? C,mon the odds are got to be 50/50 at least? I guess i'll do a compression check and see what i got and go from there.
 

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Something bent the push-rods and that is usually valves hitting piston tops. My guess is that is what killed the engine rotation so quickly when the gears initially stripped. When the pistons are going up and down and the cam stops, there are several valves, and 4 sounds like a right number, still open and those pistons still go clear to the top of their stroke. They hit the open valves and shove them closed. Since the cam is sitting there idle still wanting the valves open, something has to give and in your case the most obvious damage was bent push rods which relieved the interference and allowed the pistons to continue their stroke. However, that treats the valves and piston tops very badly so it is likely that those 4 valve are bent and there may be damage to the piston tops too. Too important not to at least do a tear down of the top end and check all that stuff for damage.
 
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