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I intend too change my AMC dist to the update idea of TeamRush. My question is: How critical is the quality of the dist cap? There are several manufacturers and each has a different price. Is mo'spensive better? I also guess the Accel wires I have,can be converted to the new style dist cap?? There were a different set of ends in the package that I hopefully kept !!!!!

1979 CJ-7 401 T18

6,784 Posts
The distributor caps very wildly in price!
Just use one that has brass terminals. Try to find a rotor that has a brass blade or nose in it also.
Aluminum is a horrible conductor of electricity. The Higher the voltage, the more resistance the aluminum terminals are. Then the aluminum gets hot, and the electrical resistance goes up even more... It's a vicious cycle and the aluminum terminals can rob you of 15% of your total spark energy in high RPM usage.
Aluminum expands and contracts a bunch when it gets hot and cold. The high voltage will heat the terminals up even on the coldest days.
As the aluminum expands and contracts, the terminal loosens up in the cap.
As the terminals loosen up, they can turn a little bit, eating a chunk off of the rotor nose, and they leak high voltage past them to the outside of the cap.
Hopefully you have good plug wire boots, and you don't take the full spark energy from the coil when it leaks...
It has been my experience with the discount distributor caps that about half of them have one or more loose terminals when they are right out of the box.
It's not a very scientific test, I just grab the terminals, one at a time with my fingers, and try to twist & wiggle them. If they move, the cap is all ready shot before it even gets to the engine.
Mo 'spensive is NOT better in all cases.
Take MSD's CDI module compared to some of the others that are three times the price, and still Inductive ignitions...
Just look for a good cap. Most of the really good caps I have tested have the visible fibers in them. They are heavier made than the flimsy plastic things, and have fibers almost like fiber glass showing in them. Those caps are virtually dielectric, meaning almost no voltage leaks through them.
They have solid brass terminals also.
The cost of the cap & rotor shouldn't really be a concern. It's a $25 investment that will go 50,000 miles, and make the vehicle more drivable.
Your Accel Super Stock wires are just fine for the factory hardware upgrades, and for the MSD module upgrades if you decide to do that later. Just change the ends at the cap, and get new boots if you have to.
Discount stores usually have a 'Lifetime Warranty' type of wire that works with the stock types of ignition systems. You will need to keep the receipt, and get new wires every two to three years.
Spiral core aftermarket wires are just about perfect, just take pains to get them together correctly. (Accel, MSD, Taylor, Ect.)
The Factory Ford wires are a pretty good set, but for what Ford wants, you can buy a set of MSD wires and have the top of the line!

If you change from the canister coil to the TFI coil, you will be increasing usable spark energy about 2-1/2 times, so spark energy control is going to be something to think about.
Again, the cost of the coil shouldn't be much of a concern, the cap upgrade will work just fine with the old coil if you are tight on $$ and can't do it right now.
I do recommend spending the $5 to $10 extra dollars and getting the premium brand of coil when you do it.
The coil is a $25 to $30 upgrade that more than likely will last the life of the vehicle, and it's compatible, even recommended by MSD, if you decide to do the CDI module upgrade later.

The upgrade article was already so long it was going to put even the worst insomniacs to sleep. I didn't include this stuff to shorten it up some. Sorry about the confusion.
I've been getting about ten emails a day asking the same types of questions.
There must be a lot of you going to do the upgrade if everything checks out....

Later folks, any more questions, just ask. Aaron.

I'm desperately trying to figure out why kamikaze pilots wore helmets...
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