Ignition coil differences

[gto78]

I'm wondering what the difference is between HEI ignition coils. My Pontiac had a stock coil which I think had red and white wires in it. I've seen the coils sold in stores and there were always two choices of red/white or yellow/white wires depending on what your car came with. What is the difference?

I was given a Hypertech coil and ignition module from my cousin who used them in his SBC. It was a different color wire than mine and I installed it anyway. It seems to work fine. Maybe one coil is made to work better with a larger or smaller spark gap, or one works better with higher compression. I'm not sure what the module differences are either except that it electronically controls the dwell time.

 

[shotgun]

Never have paid much attention to HEI coils, stock or aftermarket, never saw a difference.

Do like GM modules, number "990" is a fav having alot of dwell.

One big improvement is replacing the coil button with a low resistance aftermarket unit , coil stays much cooler and spark seems hotter.

If you listen to AM radio, you won't need at tach.

 

[gto78]

I'll remember that, 990 module and low resistance button. Your talkin about the spring loaded button that is held in underneath the coil right?

 

[shotgun]

Yup.

 

[gto78]

I found this while searching google, pretty good info. Also, the NAPA TP45 module is supposedly a direct replacement for the 990 modules with the same specs.

This comes from:
http://forums.performanceyears.com/foru ... p?t=408761
(Posted by fiedlerh)
I dug out my GM/Delco HEI book (publication SD-105) and found the following information. This is just a short summary pertaining to the polarity questions. I have more info which I will post later.

"There are three different ignition coils and three different pickup coils."

"Two of the pickup coils have opposite magnetic polarity and are to be used with the ignition coils of the same magnetic polarity."

"Opposite magnetic polarity pickup coils are needed because of the underhood relationship of the distributor location to the starter and battery cable. During starting, magnetic fields are created. The pickup coil can be affected by these magnetic fields and give false turn-on and fire signals to the module causing engine misfire. By using a pickup coil of proper magnetic polarity, the external magnetic fields will not affect the pickup coil in such a way as to give false turn-on or fire signal to the module."

"The third pickup coil has the same polarity as one of the other coils, but it has longer leads which are necessary in its application. Pickup coils can either be identified by the color of the plastic tie around the leads or by the color of the plastic connector at the end of the leads."

Blue Tie or black connector Body
1876210 (V-8) Olds (except Toronado), Buick
1891209 (V-6)
1880020 (L-4)

Yellow Tie or Yellow Connector Body
1875981 (V-8) Chevrolet, Cadillac, Olds Toronado
1880040 (L-6)
1892175 (L-4)

Clear Tie or Clear Connector Body
1876495 (V-8) Pontiac

Yellow connector
1894237 (V-6 200 CID)

Black Connector
1893894 (V-6 Even Fire 196 and 231 CID)

COIL IDENTIFICATION

"There are two types of coils that are integral with the distributors. They can be identified by the different color tach leads and the part number stamped on the coil.

The coil with the yellow tach lead (#1875894) is used on all Cadillac (except Seville), Chevrolet and Oldsmobile Toronado engines.

The coil with the white tach lead (#1876209) is used on all Buick, Oldsmobile (except Toronado), Pontiac and Cadillac Seville V-8 engines and all V-6 engines.

These two coils are very similar in appearance, perform identically, can be installed in any integral coil distributor, but are of opposite magnetic polarity. This was done to match the high tension coil to the magnetic pickup coil. The misapplication of these coils can cause hard or no starting and/or backfiring while cranking."
----------------------

 

[shotgun]

I have used the "wrong" coil before with no issues. Maybe I was lucky?

Looking at the coils the red wire goes to the same spot at the plug in the cap as do the yellow or white wires, the wires just twist before going into the coil.

I would say if you have to buy a new one, why not get the "right" one anyway?

 

[gto78]

Me too, I have the "wrong' one in there right now. I read on another site that the wrong coil can kill the lifespan of the ignition module too. To be safe I'll swap in the right coil and new module together, and verify my pickup coil too...

On a side note I'm still tryin to get my timing to reach full advance by around 3200 rpm. It pretty much stops advancing by 3200-3400, but then around 4K rpm it starts creeping higher and higher again. I've tried a few different springs and weights, still does the same thing. I found an article written by Jim Hand describing how he modified the center plate and used a certain part # weights to solve the issue instead of using aftermarket curve kit. That's the next experiment.

 

[shotgun]

How much play is in the shaft? The creep may be the gear riding up on the cam drive.

 

[gto78]

This distributor I'm messing with now doesn't really have any play at all. It doesn't have much up/down play (maybe a few thousandths?), no side to side play, and about 1/8th" rotational play. I figure inertia will hold the rotational play towards a lower timing position so that shouldn't be an issue right.

I compared it to two other distributors and the others have much more free play. However, this one with little free play has one problem. The center piece for the balance weights seems to be permanently made to the shaft, doesn't look like I can remove it and modify it.

 

[shotgun]

Sound like you got a good one.

Maybe time for some adjustable harware.

Go here: http://www.kendrick-auto.com/ignition.htm

Things get interesting when you scroll 1/2 the way down.