dembo

Allow me to ask a stupid question. I just received my stock Delco external coil for a small cap HEI. Unlike other coils I have from Pertronix, DUI, the coil is loose in it's metal ring. You can move it back & forth about 1/4" near the red arrow.
Does this compromise it's function?

Is it required to ground the the metal ring? The in cap coil grounds through the distributor but what about the external one ?

Thanks,
Nick

Big2Bird

The winding loose on the core will not compromise function.

The ground return path should be in the supplied primary plug.

cardo0

Yes as B2B said the coil has its own connection to ground in the winding's - usually winding's are connected end to end and grounded in between where the break in the circuit comes from the dist. Like the hot wire stays hot and the ground wire is controlled by the dist hall effect, magnetic, points or other crank timing device and the output current flows out the secondary winding to the rotor to the plug.

The metal core concentrates the magnetic lines of flux and allows induced currents to flow inside. I would not ground the core as that would reference the coil to batt negative potential. U want the coil to be floating as it makes spark as a function of potential difference - not as a regulated or referenced source. And i dont think u want it to move as it will receive a torque movement every time the mag field collapses and returns. Where the best position is would be a guess without laboratory equipment to measure changes in position. What im saying is if it starts to make noise or rub the coil case/epoxy u may want to use some adhesive to keep it in place.

dembo

Thank you for the answers and the clear explanation Cardo. I searched the internet on how it functions but couldn't find anything usefull.
I was thinking of a ground strap as it's mounted to the fibreglass firewall. Usually the are mounted on a bracket to the intake manifold or metal firewall. Doesn't that make a ground path as well from the ring to engine/chassis to the - battery post?
Regards,
Nick

cardo0

Thats a good question but i think u would have to remove the black coating on the coil core to get any continuity. The HEI ive had were always cap mounted and my MSD coil for the MSD hall effect dist has no ground. So why then would u add a ground to the metal core? Now i see the coil in the cap HEI does have the the metal core "grounded" but i think that ground does not go directly to chassis ground - either through the HEI module or the dist itself: http://www.crankshaftcoalition.com/w...EI_distributor.
The HEI with stand alone coils do not ground that core: http://www.jeepforum.com/forum/f8/ig...jeeps-1302352/.
Well if u ground it and lose spark u will know where to look. Without instructions to ground the metal core i wouldnt ground it directly.

dembo

Thank you for the links Cardo, very informative.
I'll remove the ground strap and take it from there
Regards,
Nick

Big2Bird

If it needed a ground strap, it would have a provision for it. It does not require one.