Distributor cap and rotor - Team Camaro Tech
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post #1 of 39 (permalink) Old Feb 22nd, 10, 09:25 AM Thread Starter
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Mike
 
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Distributor cap and rotor

Hi,

I have a 468 running a MSD system on it. The distributor is an MSD 8360. Yesterday while driving, the distributor cap flew apart. It came completely off and the rotor left the scene. I coasted to a stop and after I could not find a part store around in the area with that cap and rotor, I had to tow it home.

Anyone ever have a distributor cap and rotor fly apart like that? I haven't.

The only other symptom was previously during the drive, I noticed when I was driving up a very steep hill, I noticed if I accelerated with some authority up the hill my oil pressure actually started to fall off. It would only happen under a load. It acted normally when driving but would actually drop when putting a load on the motor.

Please help me diagnose this,

M
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post #2 of 39 (permalink) Old Feb 22nd, 10, 11:26 AM
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Red face Re: distributor cap and rotor

Yes, I've blown a cap or two apart
The cause varied for most ...
Cap retainers not properly seated or vibrated loose - cap contacted the firewall or other area due to engine flex - cap had a crack and was weak to begin with (new cap installed just a few minutes before, you could see the old and fresk crack lines) - rotor tip came apart and took out cap when it wedged in - weight popped off at speed, took out rotor and cap - wires were pulling on cap during acceleration and caused it to ****-off to one side ...
Lots of different reasons for the failure.
Look over your install carefully to see if you can identify any interference and if not, install new cap and rotor making sure they are installed and setted properly.

Oh, and carry a 'spare' until you know for sure what caused it

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post #3 of 39 (permalink) Old Feb 22nd, 10, 12:41 PM
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Re: distributor cap and rotor

i would check the bushings in the distributor. i had a msd wear and cause several different problems.
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post #4 of 39 (permalink) Old Feb 22nd, 10, 01:17 PM
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Re: distributor cap and rotor

Have seen this several times and in each case the cap had contacted the firewall and the result was cap and rotor destroyed.
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post #5 of 39 (permalink) Old Feb 22nd, 10, 02:28 PM
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Re: Distributor cap and rotor

Possibly a wear mark on the firewall?

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post #6 of 39 (permalink) Old Feb 22nd, 10, 09:59 PM
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Re: Distributor cap and rotor

Since you were losing oil pressure, and since the distributor drives the oil pump, I'd pull the dist and have a look. Hopefully nothing, but worth looking at.


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post #7 of 39 (permalink) Old Feb 23rd, 10, 02:03 PM Thread Starter
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Re: Distributor cap and rotor

I installed a bronze gear 2 years ago, could this be the problem? Need a new gear?
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post #8 of 39 (permalink) Old Feb 23rd, 10, 04:33 PM
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Re: Distributor cap and rotor

The gear could seldom cause a broken cap - unless the end play became (or was) so great from the load(s) of the gear and pump and somehow it pushed the shaft up into the cap.
Besides, the shaft is loaded downward during operation ... so I wouldn't suspect it to be the cause of a lost cap.

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post #9 of 39 (permalink) Old Feb 23rd, 10, 06:22 PM Thread Starter
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Re: Distributor cap and rotor

I wonder if the oil pressure drop during acceleration and the cap/rotor destruction are not related?


The shaft of the distributor, can that travel up and down if there is something wrong with the distributor? Like a defect or something?
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post #10 of 39 (permalink) Old Feb 23rd, 10, 06:34 PM
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Re: Distributor cap and rotor

Yes, the shaft will move up & down some normally, but not enough to disengage from the pump drive tang - unless the tang or gear are really worn, the shaft was to short for the assembly stack-up or there's something really wrong with the distributor.

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post #11 of 39 (permalink) Old Feb 23rd, 10, 06:35 PM
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Re: Distributor cap and rotor

Last time I had a cap explode it was caused by a broken engine mount. Engine hopped up and the cap hit the firewall.

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post #12 of 39 (permalink) Old Feb 23rd, 10, 07:13 PM
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Re: Distributor cap and rotor

sounds like cap hit the fire wall due to a broken motor mount
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post #13 of 39 (permalink) Old Feb 23rd, 10, 07:19 PM Thread Starter
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Re: Distributor cap and rotor

I should be able to check the motor mount problem by putting some wood under the oil pan and then a floor jack against that and lifting it a bit right?
Then it should let off tension from the front coil springs relatively evenly if all is good. If a motor mount is allowing the motor to move, the jack should lift the motor on one side right?

Or is there a better way?
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post #14 of 39 (permalink) Old Feb 23rd, 10, 07:59 PM
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Re: Distributor cap and rotor

Quote:
Originally Posted by Vintage 68 View Post
Besides, the shaft is loaded downward during operation ... so I wouldn't suspect it to be the cause of a lost cap.
I think if you look again, you'll note that the distributor mainshaft is loaded upward during operation; that's why there are hardened shims between the top of the gear and the bottom of the housing and why that's the only part of the mainshaft that gets engine oil. The Delco distributor assembly drawings clearly show that the thrust of the gear is upward, against the housing.

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post #15 of 39 (permalink) Old Feb 23rd, 10, 08:40 PM Thread Starter
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Re: Distributor cap and rotor

Quote:
Originally Posted by JohnZ View Post
I think if you look again, you'll note that the distributor mainshaft is loaded upward during operation; that's why there are hardened shims between the top of the gear and the bottom of the housing and why that's the only part of the mainshaft that gets engine oil. The Delco distributor assembly drawings clearly show that the thrust of the gear is upward, against the housing.
So what does that mean in this situation?
Does that mean the shaft or something on the dist could have rode upwards causing the rotor to contact the cap and destroy it?

Incidently, I have about 10 WOT passes and about 4 combined hours of cruising on that car since I installed the bronze gear in it. (I was told that a roller cam should have one so I put one on)
How long do they last? Should I replace it?

Just wondering if my oil pressure dipping during hard throttle acceleration and then the distributor cap blowing apart could be related.
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