Gasser/Chevy Help... broken Distributor gear???

[BK]

Buddy of mine has a 67 Vette with a built up 350, new engine, very low miles. . maybe 5K by now. New aftermarket distributor.



He was driving at about 35mph on his local main street.

while cruising. . he heard two loud backfires. . motor dies and winds down. . he rolls off to the side of the road. . can't restart.



Towed it to his house.

Initially found no spark... while turing the engine over and trouble shooting, rotor was turning at one point. . double check, now theres spark.

Pull the distributor out. The driver gear on the distributor has a busted tooth. It's a metal gear.



???????



Guessing the back firing was from the loss of correct timing when the tooth broke.



I've never seen this happen before.

Are there any common OTHER failures that will eat the distributor gear?

Haven't tried to turn the oil pump yet.

Could a jammed oil pump cause this? I've seen oil pumps go away and loose pressure. . but I havent seen one bind up.

Engine sounds totally normal when driving it with the starter.



I'm sure he needs to pull the motor and drop the pan to make sure everything else is in order and pull any fod out.



Thoughts please?

 

[gitchesum]

I've had the oil pump freeze up and twist the pump shaft into a spiral but ever have had a dist gear break.



Could have just been a bad one??

Cam wasn't hurt was it?

 

[BK]

So far it seems the cam is ok... but he hasnt pulled the intake off or valve covers to see if all the valve train is moving.



No funny sounds out of the engine when turning, seems the compression is building evenly during cranking.





He's out of time this weekend. next weekend, it comes apart.

 

[dmurdock]

Yes, the cam gear drives the distributor, and the oil pump shaft plugs into the bottom of the distributor gear... so basically the cam gear drives everything.

 

[BK]

...

talking about it more...

using the rotor to turn the distributor, while the broken teeth are facing the cam's gear...

it seems the oil pump turns fine.



But he said whats strange is that the teeth are worn very uneven and very noticable. Alsmost as if it ran off center... the side of the gear with the broken teeth ran at the tips of the gear teeth. . opposite side looks much better, the teeth arent worn down. As you go around the gear to the broken teeth, the tips of the teeth become thinner.

The shaft turns true, the distributor fits tight in the manifold, the distributor's shaft bearing is tight and feels good.



Again, not being a chevy gear head...

Could there be an issue with getting the wrong gear from MSD (maker of the distributor) and or wrong gear on the cam. . so engagement wouldn't be correct. . like a badly shimmed ring/pinion.

Or missalignment due to - too thick of a intake manifold, or if the manifold sat to high due to the heads?





thanks. .

 

[E7mack96]

Is it a roller cam???

Most rollers need a bronze distributor gear. Could this be the case??

 

[Champane Flight]

Gear

If I am not mistaken the dist gear has a driven pin in it. To replace just drive the old pin out and replace the gear, replace the drift pin and voila. Now when putting it back in check for play in dist, if there is none, you are too tight. You will need to shim dist base. It sounds like you were a tad too tight, this happens a lot woth after market dist. Yes I would check oil pump drive and clean out pan. Also check cam gear for damage.

 

[BK]

"-E7mack96 Most rollers need a bronze distributor gear. Could this be the case?? "



Do you mean a roller valve train??

The gear was steel of some sort...

Not bronze. .





Champane Flight,

Yes there's a pin to replace it.

Ah. . very good info. . just what we were wondering. tnx







great info/questions. .

thanks

 

[tcourse]

Bronze gear

I believe the reason most use the bronze gear is to avoid camshaft damage.



TC

 

[dmurdock]

Before you get to deep in a repair, I'd put a new distributor gear on it, coat it in some really sticky grease (say white lithium), install the distributor and then crank the engine by hand. You can then pull the distributor and get a feel for how the gears are lining up. As mentioned earlier, there should be some play in it... . not a lot, but "some".

 

[jimk]

roller cam shaft

I had a 600 isky roller in my 302 chev and I had to run a bronze gear on the HEI. The camshaft is steel billet not cast. I am not sure what they run now a days but back when angle plug turbo head were they thing to run that is what you used. The heads were mostly devcon. My spelling is not great,

lol Jim K