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Old 09-14-2002, 11:27 AM
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Post Can anyone explain this??

I just replaced the timing chain and gears, and the vibration damper in a 69 350 engine with the stock distributor and pertronix module, Holly 4 barrel carb. I set the timing at the recomended spec of 4 degrees BTDC. I ran it fast, slow, let it idle, applied the brakes and gave it some gas to check it under a load and the car ran perfectly, under any test I put it thru in the driveway.

When I drove the car slowly down the street, accelerating slowly to 20 miles per hour, the car started stumbling and stopped running completely. I pulled over to the side of the road, and the car started back up with no problem. I did this several times and had the same problem each time.

I moved the timing up from 4 degrees BTDC to 10 degrees BTDC and the problem disappeared! Can anyone explain this???

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Old 09-14-2002, 12:41 PM
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sounds like a fuel flow problem, not much info, but since the pump had to be off, that's where I'd start. Most of the time when something is a miss after some type of work it can usually be traced to something in the work, even for professionals. Since the engine wasn't under load in the drive it wasn't drawing as much fuel as it does moving the car. Might check the soft line to the pump from the tank, maybe kinked or cracked and drawing air.
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Old 09-14-2002, 08:59 PM
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It's interesting to me that moving the timing solved the problem. I wonder if your balancer and or timing tab is out of whack. Did you reference your TDC mark with actual TDC on the engine? It could be an entire myriad of things causing this, but if the timing really did solve it, you have to look at your chain installation or your balancer, and timing tab and verify that everything is on the money. Did you remove the fuel pump during this work? You wouldn't have to remove the fuel pump to change the timing chain and balancer. Did you upgrade your distributor during this operation or was it left alone?
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Old 09-15-2002, 02:34 AM
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[quote]...accelerating slowly to 20 miles per hour, the car started stumbling and stopped running completely. I pulled over to the side of the road, and the car started back up with no problem. I did this several times and had the same problem each time.<hr></blockquote>

That's what I am thinking...something amiss in the distributor. Check the advance weights for freedom of movement and operation of vacuum advance connected to ported vacuum source.

As has been ably suggested before...connect a dwell meter and see if the dwell remains fairly constant. Might be an out of calibration dist. and the chain replacement has it confused...
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Old 09-15-2002, 02:41 AM
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I have read that a lot of installers have had problems with the PERTRONIX due to confusing installation instructions. While the following -URL-(click here) is mainly FORD related, maybe one of the problems carried over to your installation.

Maybe it will help...
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Old 09-15-2002, 03:36 AM
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I've also had trouble with the Petronix ( on a Mustang that came into the shop) when it was removed and returned to points it worked great. The wrong coil had been put on the car (one off a transistorized ignition 427) and that may hve triggered the failure, I came in after the install and just know that the removal of the Petronix cured his miss/hesitation problem.
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Old 09-15-2002, 08:29 PM
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This is one of the strangest things that has ever happened tome working on a car. Before I put the new timing chain in, the car ran ok with no problems. The chain had alot of slack in it so I wanted to replace it. I had the pertronix module in there for a year prior to this. I did not touch the distributor or the fuel pump. I double checked the timing marks on the cam and crank gears and installed a new aftermarket damper. I checked the fuel pump hoses, and distributor advance and it all looked good. I am still completely bafeled by this.
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Old 10-05-2002, 06:59 PM
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Just wanted to let everyone know I found the problem with the original post. It turned out that the wires that come out of the pertronix modulule had worked there way up into the advance mechanism and eventually the insulation was worn off, causing an intermitant ground. I used liquid electrical tape on the bare part of the wire and wrapped electrical tape around the wires just as they came out of the distributor to keep them from getting back up into the advance mechanism. Car runs great now.
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Old 10-05-2002, 07:06 PM
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Isn't it always the simplest of things?
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Old 10-05-2002, 07:32 PM
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Not to change the subject, but I just installed a Pertronix on a Ford 390, and the box said they have sold over 2,000,000 units. Take that times eighty bucks and do the math. Wish I would have thought of it. Cha-Ching!
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