The Stovebolt Site Forums The Shop Area Engine Shop Caddybolt problem

Last fall I purchased a 1969 Sedan Deville. 110k one owner. The only thing that is not original is the electronic ignition. It has a Napa "brain" that looks like the Chrysler one in my Dodge.

Here's what happens: It starts easily, and runs smoothly. For about 20 minutes, then it will cough,sputter and finally backfire so hard to litterally blows the seams apart on the muffler. The first time I thought it was just a fluke. So on goes a new muffler. I'm on my third muffler and getting very tired of this. :mad:

The timing is set correctly; new plugs,wires,cap and rotor, fuel filter and coil. Can the pick up module in the dist go bad? I wish it still had points! It came from the factory that way; good enough for me!

Also, it has 2 ballust resistors. One at the coil and one on the firewall. This too seems strange.

Any ideas? :confused:

Is it a 429, or a 472 engine? I think either one can be upgraded with a HEI ignition system for a 500 engine from about 75-up, and you can pitch that aftermarket setup. All that's required to make that one work is a heavy wire from the ignition switch to the distributor, (about a #10), to replace the resistor wire used on the point-distributor model. No ballast resistors, or oddball parts to worry about! It should be a drop-in fit, as the 429, 472, and 500 engines use the same basic block setup.
Jerry

As HRL said, if you're not worried about car-show snobs, convert to HEI. One consideration is the rotation of the distributor rotor. Unsure if caddy engines turn clockwise like a chevy, or counter-clockwise like a Pontiac. Figure out which way it turns and get the corresponding distributor. Not sure if you'd have to use a distributor out of a caddy, or if another GM unit would work. Compare shaft, gear and oil pump drive tang dimensions on your distributor to the candidate HEI unit. You'll then have to re-curve the HEI to get the optimum spark advance for your engine. Still not a big problem.

I've used 14 gauge wire to power HEI ign systems up to 5,000 RPM. Don't wanna turn a stock-rod caddy engine much past that anyway. HEIs only require one wire from a switched 12 volt source to run. Most important thing is to eliminate ballast resistors or resistance wire in stock distributor power circuit(s). Other slight wiring mods may be needed to get power from key to HEI unit during cranking and run positions of key. Or you could convert a stock points-style distributor with a Petronix kit for a stock appearance. Either way, we can talk you thru it.

good luck

HRB (aka CH)

Got a little firsthand experience with this one! The Caddy distributor has a different housing height than a Chevy, and I think it's a left-hand rotation, also. The shaft length is the same, but it has a different dimension from the block to the top of the distributor. You'll need a Cad distributor, probably from a 500 CID engine. If one isn't available from a wrecking yard, NAPA, or some other professional-level parts store probably has rebuilt units available by special order.
Jerry

i see cad heis on ebay sometimes.

T.Mott,

See no need to worry about HEI. Get one out of Caddy in the local junkyard, drop it in and live happy with it. I used it in a bunch of cars, both of mine and from some fellows, and all I can say is that it is just the more reliable sotck ignition system I've ever used. Just get one for the intended use and no problem.
But to be honest with You, I'm not sure about blaming your ignition system for the misfire. Some other problems may be going on. Are You definetively sure there is nothing else wring with it? Just imagine if it's not the lifters i.ex, weak valve springs, You say the engine runs smooth cold, then gets hot and starts misfiring. Is carb problems totally out of question? Guess it's a q-jet, huh?