1967 won't run after 30 minutes

[Lee B.]

It's me again. I have my dad's 1967 Convertible. I had the car completely restored and it has never run right. It has consistently run great for 20 to 30 minutes. Then it starts to backfire and run like crap. Here is the deal: I just had the carb professionally rebuilt by Eric Jackson who does beautiful work, just replaced the rotor, distributor cap, condenser, points, checked the plugs and they are not fouled. Set the dwell to 30 degrees, and set the static timing to 12 degrees. Drove it for 20 minutes or so and it ran great. Stopped to get some gas, 89 ethanol free, and when I mashed the gas to the floor, if started to stumble. Made one more stop and the car and when i got back into the car, it would barely run. It would idle fine, and rev fine, but when it was put in gearn and had load on the engine it started popping and backfiring. Limped home without revving over 1500 or less. I am at my wits end. Been screwing around with this car for over 2 years and cannot get it to run for longer than 1/2 hour. Please help me out before I take a sledge hammer to this car.

[Donald O.]

Re: 1967 won't run after 30 minutes

Could be either the coil or the ballast resistor, but I'm betting on the coil.

Don

[Timothy B.]

Re: 1967 won't run after 30 minutes

Lee,

I agree with Donald, if it's got one of those reproduction coils try a NAPA IC-12. Also, make sure to check that the coil is installed in the bracket with the primary terminals parallel with the firewall.

[Frank T.]

Re: 1967 won't run after 30 minutes

I had the the same problem mine was ballest resister good luck

[Edward J.]

Re: 1967 won't run after 30 minutes

Lee, another item to look at is the wires inside the Dist. there is a ground on dist. plate, and the wire on the points will sometime get pulled on when the vacuum advance is operating , this can cause the kind of driveabilty problems you maybe having.

[Edward B.]

Re: 1967 won't run after 30 minutes

Symptoms are indicative of a bad coil - please report back to all of us well wishers.

[Joe C.]

Re: 1967 won't run after 30 minutes

One way to check for a weak coil is to keep it cool by keeping the rear of the hood open and removing the radio noise suppression shielding. A better way is to temporarily relocate it to a cooler spot. Generally a coil on its way out will fail as it gets hot. Using a wrong value ballast resistor (early 1964 and prior) will hasten coil failure as too low resistance in the ballast causes the coil to work harder than it should.

[Lee B.]

Re: 1967 won't run after 30 minutes

Thanks to all. I am in DC with my family for spring break. Stopped on the way up at Zip and picked up a new coil and ballast resistor. Will put on and try Thursday or Friday and report back.
Lee

[Donald O.]

Re: 1967 won't run after 30 minutes

Well, what are the results?

[Lee B.]

Re: 1967 won't run after 30 minutes

I apologize for not responding, but I have been building a new garage and have not had a chance to really test it. Need to quit my day job so I can get all the stuff done at the house, but then I don't know how i would pay for it. Hope to post by Wednesday at the latest.
Lee

[Duke W.]

Re: 1967 won't run after 30 minutes

Next time you drive the car bring a jumper wire with alligator clips on the ends and a golf tee. If the problem occurs pull over, shut off the engine, open the dist. window and connect the jumper between the breaker plate and any good ground. Disconnect the VAC and plug the signal line with the golf tee to prevent breaker plate rotation in response to VAC movement. You'll will need to set the idle up, and it might run a little hot in traffic.

Search for a thread stated by me in Dec. '12..."L-79 distributor blueprint/overhaul..." It explains the problem and an easy fix without having to remove/disassemble the distributor to crimp/solder on a new ground wire onto the bottom of the breaker plate.

Do the above before you install the coil or ballast. Maybe you don't need them. If the above doesn't find the problem swap in the coil and ballast in one at a time, not at the same time to help you isolate the problem. This is the "scientific method" - make only one change at a time. If the ground is okay, try the new coil first.

Checking all ignition electrical connectors including cowl electrical connectors and breaker plate ground wire should be done with these symptoms before you start swapping parts. Also carefully check primary and plug wires and make sure they are not worn and shorting out on the distributor shield.

I know of no source for new breaker plates. The ground wire is part of the assembly, and most guys don't know that on a 30-50 year old car, most of which probably have the original breaker plate, it is a failure just waiting to happen.

Duke

[Lee B.]

Re: 1967 won't run after 30 minutes

I checked the ground wire in the distributor and it is good. Wiggled it all around with ohm meter on it and it never lost continuity. I changed the ballast and everything seems to be working as it should. I had changed the ballast before so I didn't think that would have been it. I will continue to drive it this weekend and see what happens, but it drove great today. Thanks again,
Lee

[Ralph E.]

Re: 1967 won't run after 30 minutes

I checked the ground wire in the distributor and it is good. Wiggled it all around with ohm meter on it and it never lost continuity. I changed the ballast and everything seems to be working as it should. I had changed the ballast before so I didn't think that would have been it. I will continue to drive it this weekend and see what happens, but it drove great today. Thanks again,
Lee

Did you changed just the ballast or did you change both the coil and ballast?

[Douglas L.]

Re: 1967 won't run after 30 minutes

From my experience with similar engine performance gremlins, checking everything that has been mentioned are all good places to look. But also:

Double check your plugs. A couple of years ago, I changed the plugs in a ski boat with marina recommended replacement plugs. Ha - what a joke. The boat would not even get up on plane. The warmer the engine got, the worse it ran with more backfiring through the carb and loss of power. The recommended plugs were too hot. Changed the plugs back to the old plugs and off it went.

Rebuilt carbs are not always perfect. Had the carb rebuilt on my 427. It was beautiful looking. It ran OK at idle and also when the motor was cold. As the motor warmed, the worse it ran. At operating temperature, I could not get past 55 mph. So, I tried another carb(also rebuilt) and the difference was astonishing. So, if you can, try another carb.

I still have a gremlin in the 427. It runs beautiful. But, for some reason, you can be driving along at 55 or 60 and the engine will just quit. So, I turn the key off and then restart and amazingly it runs again. So, still trying to sort this one out.

[Lee B.]

Re: 1967 won't run after 30 minutes

I was trying one thing at a a time. Just changed the ballast, but what a difference it made. I had changed it out a year ago, but I guess that one was bad. Will drive some more this week, but fingers crossed, I have not been able to get it to act up again. Will check plugs again if things go south.