Prestolite dizzy question

ronmc1954

ronmc1954

Member
I pickup this dizzy on ebay and I had some questions.
Dizzy id:
IH 496004c91
prestolite
idn 4002h 8s9

is this the electronic ign. I need to worry about leaving the key on? Will it fry if I do?
Clarify, no gold box right?

Would "you" use it to replace your points?
Can you use a full voltage coil?

dscf1492.jpg


Thanks
ron
 
Nice find ron...if it's functional!

The IH p/n you posted is correct, but look again at the "idn" number which is waht matters in the prestolite world. That IH p/n should carry a presto number of idn-4002r.

That distributor is correct for a m/y 79 sii and will exhibit a dwell (non-adjustable) of 28*>34* as compared to an earlier version with a dwell setpoint of 26*>32*. The air gap on all idn-series distributors is 0.008" measured with a non-magnetic thickness gauge, so the difference indwell factor is a slight change in the electronics.

It also has more total advance spec'd into the mechanical advance unit and the initiation of mechanical advance occurs justa tad later.

This is no big deal, and in fact, that distributor would be a slightly better choice in a performance engine build

full service data is contained in the cts-2313 service manual set for the "later" Scout II platform.

This distributor/ignition system uses no "ballast" resistor or resistor wire in the primary circuit, it needs to see switched b+ only at the positive coil terminal.

The coil however can be the same coil as used in any IH sv application, either breaker point version or electronic ignition. Thus...any 12vdc-rated coil with a primary resistance value between 1.5ohms and 2.0ohms will work just fine.

All the ignition components are contained in the electronic module mounted under the trigger plate, there is no external control unit for this distributor needed. That "third" white wire with the female plug that comes off the harness is a feed to the dtm module which is an emissions device.

For installing this distributor in any sv app, all that's needed is to connect the red wire to the coil positive terminal, and the brown wire to the coil negative terminal...just like when installing a pertronix conversion. Of course, the coil must receive b+ from an ignition switched source with the switch in both the "start" and "run" position.

As for damaging the electronics if the ignition switch is left "hot" without the engine running...I don't know. But that is never a good idea on any ignition system. Some will say "no", some will say "I don't know"...why risk finding out...just don't do it!!

Do not attempt to use a Holley 1500/1510 distributor cap on this unit, it will not index correctly and the presto rotor tip will not phase correctly with Holley cap terminals. The presto cap terminals inside are "flat" and out of phase as compared to Holley. The presto cap uses male terminal studs, the Holley cap uses female terminal receptacles.
 
Thanks for the info michael; I actually bought 2 dizzys one functional and one not. Both out of a 79 Scout ($15 for the pair)

your right about the idn, it is a 4002r 8s9, the other is 7s9.
Neither came with rotor or cap, won't happen to know a part# would you?
If I am not mistaken the white wire can be used for a tach, correct?

Ron
 
No, an aftermarket tach connects to the coil. Without looking at the output on the white wire with a scope, who knows what kinda signal it is?

A typical cap p/n would be like an airtex 5d1176, anyone can do a lookup for that. Rotor typical would be: airtex ar1103 (standard al171).

I made contact with a regional prestolite warehouse distributor last week. I've forwarded a list of IH-related idn numbers to the sales rep so he can research availability on service parts and complete units for us.

The prestolite company that manufactured that distributor series is not the "same" company that currently manufactures electrical components, motors, etc. And not the same company that currently manufactures electrical apparatus/wire/etc. Under the "other" prestolite banner. Things have changed several times in the past thirty years!

The largest market for prestolite distributors was in the marine engine conversion bizz, they also did some joint venture stuff with autolite/Ford (as did Holley).

If the electronic module is punky, then those are easily converted to a pertronix unit. The prestolite wd checked stock on p-trons for the idn series for me and they got plenty on hand!
 
Well here it is sat and I went to put in the prestolite dizzy and found I don't have the dust cap for the 4002r and the cap won't fit without it. Does any one know where I might get one?

Ron
 
Hi, I thought I would give this post a little bump. I am still looking for a dust cover for this distributor. I did get it installed sun morning and it works great! I made a dust cover out of some plastic, like the heavier "bubble" package plasitc. I cut out a square about 5x5 and cut a hole in the middle for the rotor. I then took an empty 3/4 masking tape roll and trimmed it to fit inside the dizzy for a form. Layed the palstic on and used a heat gum to soften it and while it was still warm snapped the cap in place and let it cool. Trimmed it up, and it seem to be fine but I still want the oem cover.
But as I said it runs great, I have 30* dwell which I might try tweeking a little, 32* would be a little closer to michael's specs.

Later
ron
 
ronmc1954 said:
hi, I thought I would give this post a little bump. I am still looking for a dust cover for this distributor. I did get it installed sun morning and it works great! I made a dust cover out of some plastic, like the heavier "bubble" package plasitc. I cut out a square about 5x5 and cut a hole in the middle for the rotor. I then took an empty 3/4 masking tape roll and trimmed it to fit inside the dizzy for a form. Layed the palstic on and used a heat gum to soften it and while it was still warm snapped the cap in place and let it cool. Trimmed it up, and it seem to be fine but I still want the oem cover.
But as I said it runs great, I have 30* dwell which I might try tweeking a little, 32* would be a little closer to michael's specs.

Later
ron
Click to expand...

Good injinuity:yesnod:
 
ronmc1954 said:
hi, I thought I would give this post a little bump. I am still looking for a dust cover for this distributor. I did get it installed sun morning and it works great! I made a dust cover out of some plastic, like the heavier "bubble" package plasitc. I cut out a square about 5x5 and cut a hole in the middle for the rotor. I then took an empty 3/4 masking tape roll and trimmed it to fit inside the dizzy for a form. Layed the palstic on and used a heat gum to soften it and while it was still warm snapped the cap in place and let it cool. Trimmed it up, and it seem to be fine but I still want the oem cover.
But as I said it runs great, I have 30* dwell which I might try tweeking a little, 32* would be a little closer to michael's specs.

Later
ron
Click to expand...

Don't sweat the dwell reading you see ron...when using an analog meter it displays an "average " of individual dwell factors while the distributor is rotating. If you see the primary circuit display onna scope, you would see the individual dwell factor for each cylinder/relutor segment. The dwell varies a tad due to "runout" in a distributor that has miles on it.

Again, nothing to be concerned with, an inductive ignition system always needs a typical dwell factor of 28>32* to provide proper ignition coil saturation, whether breaker point trigger, hall effect trigger, or magnetic trigger.

I'm working now on obtaining those dust caps from a prestolite wholesale warehouse distributor along with some other prestolite service parts. But I won't be following up on this until we get home around the 22nd.
 
Thanks for the info michael, I have not went full voltage on the coil "yet" it runs great with the resistance wire. I want to pick up a new coil, I don't know if the coil I have says "resistor only" on it or not, so I thought I would play it safe for now. My 75 has the same set up only with a ballast resistor and I have never had a problem running with the resistor installed. I would imagine I will get a better spark with a full voltage coil. I think I have found a used dust cover up in yankton sd, I will find out next time I am up that way.

Looks like the ralley turn out great! Man we got snow here:shocked:

ron
 
ronmc1954 said:
thanks for the info michael, I have not went full voltage on the coil "yet" it runs great with the resistance wire. I want to pick up a new coil, I don't know if the coil I have says "resistor only" on it or not, so I thought I would play it safe for now. My 75 has the same set up only with a ballast resistor and I have never had a problem running with the resistor installed. I would imagine I will get a better spark with a full voltage coil. I think I have found a used dust cover up in yankton sd, I will find out next time I am up that way.

Looks like the ralley turn out great! Man we got snow here:shocked:

ron
Click to expand...

Pay no attention to any statement on any coil regarding "use with resistor only", "do not use with resistor", etc. All that statement does when printed on a coil is cause much confusion. In reality, what should be printed on the can is a statement regarding what the specific primary and secondary resistance values for that actual part number should be. Using that information, a correct coil for any engine application May be determined.

The only thing that matters is that the coil needed for any IH sv engine app, whether breaker point, gold box, prestolite, delco, whatever distributor, needs a coil with a primary resistance factor between 1.5 and 2.0 ohms. So that makes things real simple...the same coil is used with all oem ignition system apps!

And the "resistor wire" and a "ballast resistor" perform exactly the same function electrically-speaking, but are simply two different forms of a resistor or resistive element.

Yes...the prestolite system will "run" on a ballasted (reduced voltage) primary feed, but can't function at it's full potential.
 
Well here is what I found on the resistor wire. There is a braided (heat resistant insulation) running from the + side of the coil to the "ff" slot on the bulk head connector. Voltage on this wire is 12vdc in run and start. I measured the voltage at the bulk head connector and at the coil, both read the same. So evidently I do have b+ supplying the coil and the prestolite dizzy.
So I assume the po had all ready put a full voltage coil on the 74.
Anyway it runs great and I don't have to mess with the points anymore.

Ron
 
You must log in or register to reply here.
Back
Top