Max length on primary coil->cap wire?

[crazypete]

I searched the archives but I could not find a direct answer to this simple question so here it goes:

What is the longest that one could make the primary coil to cap wire?

I ask because after water splashed into my fender and took out my MSD, I decided to move EVERYTHING more complex than a simple wire inside the car and I have most of the wires moved back there already awaiting my summit order. I moved the starter relay, the future Hi-6 box and PS-92 coil up under the dash. Now....is there any real disadvantage to having like 8-9 feet of primary wire on a coil? Thats what I will need to reach the cap up front. These are the whimpy 70's 7mm wires since I have the cap with the recesses instead of the big cap with the nodes sticking out and these are the only ones that would work. I assemble longer wires by sticking the wire's snap fittings inside eachother and crimping and then sliding the boot over to insulate

Thanks in advance and happy motoring!

Crazy Pete

 

[jrichker]

Most high voltage spark plug wire has about 2000 ohms per foot resistance. Some of the Taylor & Accel wires have less, since they use a spiral wound metal conductor. I would not have more than 3 feet of regular high voltage wire, maybe 4 1/2 feet of the spiral wound metal conductor wire. The longer the wire, the greater the loss due to resistance and the greater the noise in the electrical system. That electrical noise can adversely affect the computer & radio, as well as play havoc with every radio and TV in a 50 foot area. All in all, a long high voltage wire from the coil to distributor is not the best plan.

I would build a waterproof box for the MSD, or put the MSD unit inside the car. Some guys mount them under the seat. Then run the coil in the standard mounting spot & run long wires from the MSD box to the coil. Safer, less loss & electrical noise. You could use regular 14 gauge stranded electrical wire and then put some tinned copper braid shielding over it to make it look neat and eliminate any electrical noise or RFI (radio frequency interference).

 

[crazypete]

Are you serious about that messing up tv's in a 50 foot area?!? That pimps.

I bet it would screw up the computers in policecars too! They would try to give chase but their rides would stall out and his radio wouldnt work so he couldnt call for help. EMP blast!

Even better, it would knock out all the cellphones around me!



Now on the serious side: I've seen people mount the tubelike shaped coils above the intakes on a bracket to the right of the distributor but my archive raking came across some folks complaining about oil leaking from their coils and the autopsy was heat frying the coil. I guess I could lash it to the side of the distributor. Is that going to cause all sorts of noise too or is that more ok? I would rather run the 2 small booster wires from the ignition across the car than run a live 60k volt wire.

I've touched a primary wire with the key on and engine off and that certainly woke me up after I peeled myself off the wall of the garage