1967 427 400HP quits when hot

[Jeff C.]

Car has older electronic conversion kit brand unknown. runs like top until it quits. history: drove 16 miles car then car started to run rough and quit. let set for 45 min and it stated right up ran for several min then I shut it off. 4 hrs later started up and the engine and it quit in less than a min. had to tow car home. a week later the car started right away and well. I ran it for 15 min no problems.Today started again and ran for about 20 min with no problems. I am thinking it is a coil problem or conversion kit problem Any thoughts
Thanks,
Jeff

[Jim D.]

Re: 1967 427 400HP quits when hot

Definitely an ignition issue. Need more info. on your "conversion" but everything you've posted points to the coil.

[Edward D.]

Re: 1967 427 400HP quits when hot

As Jim says, for sure an ignition problem. Probably the coil, but may be your conversion module. Is your conversion a 2 wire (pertronix type) or a one wire (Breakerless SE), or an outside MSD (multi spark discharge) type add on box? Check how many wires coming out of under the distributor to coil to determine. Each of these have different coil and ballast requirements. Are you using a stock Delco coil? These require a ballast resistor (on firewall). Sure they will operate for a time without one, but will ultimately die due to over voltage (the ballast resistor reduces ignition voltage to appox 9 volts). Pertronix recommends an internal resistor coil and likes to do away away with the ballast resistor but you can use a stock coil with the resistor. The Lectric Limited breakerless SE (which has only one wire) uses the stock coil and ballast resistor. This is what I prefer since you cannot tell its there without removing distributor cap. However, I have seen failed ones in a couple of cars. If you don't want stock contact points & condenser, and don't mind an extra wire (for 12V to the module), then the Pertronix LS (Lobe Sensor) module is the way to go. If you have a driver car and are not concerned about appearance, the MSD type ignition box will give you a better longer spark event (for easier starting) but otherwise no real benefit. I generally remove them from cars that come into my shop with ignition problems.

[William H.]

Re: 1967 427 400HP quits when hot

Sounds like spark plug wires

[David M.]

Re: 1967 427 400HP quits when hot

Verify you do not have spark when this happens. If you do have spark then we need to go in a different troubleshooting direction.
Buy an inline spark tester, The type that installs between the plug tip and wire end and has the little light that flashes. You can actually hook it up when its cold and drive it.

I agree its likely the ignition system breaking down due to increased resistance from bad grounding, which increases more when hot. The high resistance will take out electronic ignition modules.

Look at the engine grounding.

If the ground strap from the engine block to frame, the negative cable from the battery to frame have a compromised connection this will take out distributor modules, MSD boxes, Mallory systems etc...and it will tax the charging system as well.

Replace any missing braided ground straps. Not sure if C2s have these?

Ohm the battery cables. If they are brittle or have high resistance replace as needed.

[Duke W.]

Re: 1967 427 400HP quits when hot

Next time it quits ground a loose plug with a test lead. Pull a plug wire and attach to the grounded loose plug and check for spark while cranking.

Another ground problem can be the breaker plate ground wire. It's constantly being flexed by VAC action. If you get a no start condition check for continuity between the breaker plate and ground. The last distributor I overhauled barely had two stands left and broke off the breaker plate as I removed it, and that car had only about 60K original miles. Napa sells a replacement that can be installed with the distributor in place.

Duke

[Jeff C.]

Re: 1967 427 400HP quits when hot

Thanks everyone,
I will be checking everything you mentioned. It turns out that the electronic conversion kit is one made by Crane Cams. Also the previous owner installed an after market alarm and the car also has original AC. Lots of wires I don't recognize. Just a note this is part of a 15 car collection that I try to maintain for a good friend and I only go there 1 or 2 times week.
Jeff