350 buck truck Mallory Unilite Thread

[Rusty Scout]

I found these used parts on craigslist in plumas county for a good price. This mallory unilite dist unit will replace the Holley ghost box dist with ignitor retrofit. The Holley seems ok but it is curved for egr/emissions and is difficult to recurve or find new vac advance units. My 1975 off road race truck has a 304 with an isky 256 supercam with the egr system "optimized" with a block off plate. The 2210c carb will be improved by removing it from the system and swapping in a new 2300 set up by mm but that's down the road after the tanks get finished.

The story was the dude went for a dui and that's why it was for sale. If I was smart I would have made him bench test it in front of me before I paid him but in the spirit of binderhood I was happy to hand over the cash for this:

 

[Rusty Scout]

So now after 6 months in a box stashed in my IH pile it's time to see how badly I got ripped off. I have heard of folks burning these unilites up by not following the proper installation directions. Judging by the character of the IH dude that I got this from and all the goodies that seem to be intact I think it will test out all right. Only one way to tell though.

 

[Rusty Scout]

I have been warned about end play and I am wondering if that issue is caused by these distributors requiring you the IH guy to supply and install your own distributor gears.

My endlpay seems to be .025" with a feeler gauge. To attain the .010-.015" spec I will be needing the proper spacer. What's the best way to go about this if the electronics check out ok?

 

[Rusty Scout]

Here are some other pics that just show the general condition of the distributor:

 

[Michael Mayben]

Anyone who would give up the mallory stuff for a dam hei sparker is crazy as hell...the mallory setup is far superior in my book.

So all ya need to do is remove the drive gear, install a steel 0.010" shim, and then stick the gear back in place, carefully seating the spring pin.

With a mallory, once the spring pin is driven out, the gears normally pull off with your hand as they are not a press fit. And since the gear is already in place, it's has to be a "centered" hole version so there is no orientation issues when reinstalling the gear, just slide it back on until the spring pin hole lines up.

Of course, check the vacuum can for serviceability.

The advance system on all the variations of the mallory distributor is fully adjustable as for "curve". Another major advantage to using these items as they are the only aftermarket replacement distributor manufactured for direct installation in an ihc-produced I-4/sv engine.

Download the mallory instructions/tech info if you haven't already done so. I've posted 'em in this thread which is required reading for mallory stuff:

http://www.forums.IHPartsAmerica.com/ignition-tech/4622-ignition.html

 

[Rusty Scout]

So in layman's terms if I interpolate the underhood unilite testing instructions correctly for a bench test .... I connect a 12v+ source to the input side of the mallory ballast resistor and the red unilite wire to the output side of the ballast. The brown wire on the unilite harness goes to ground. The green unilite wire which normally goes to coil negative will instead go to the positive red lead of my voltmeter and the negative black lead of my voltmeter will go to ground. Then with the rotor/shutterwheel out I should be measuring 12v with optical sensor not blocked. With optical sensor blocked with a credit card or whatever I should get 2v or less. Eh? Before I fry something thought I would run it by tech moderator.

 

[Dealbreaker74]

You don't want to power the distributor through the ballast resistor, just the coil. Red wire from dist goes to the the same terminal on the resistor (call it an input if you want, though resistors aren't directional) that the 12v source gets hooked to. Distributor now has a full 12v for power. The "output" of the resistor goes to the + side of the coil. Now the coil will be protected from over-voltage. The green wire from distributor goes to the - side of coil. Brown wire gets tied to a solid engine ground point. With the distributor installed take the rotor off to expose the led pickup. Put the coil wire near something to ground, and with the key on, use a piece of paper or business card to block the led. When you remove it, the coil should spark.
Here's a pdf of mallory's instructions:

 

[Rusty Scout]

So I guess my confusion stemmed from the statement that "failure
to use an ignition ballast resistor will eventually destroy the unilite ® ignition module." I took that to mean that the unilite was directly protected from the ballast resistor. But alas now the mallory wiring diagram makes sense. Rust between the ears.

So to bench test this thing to verify if the unilite module has not been burned up by the previous owner before I take the trouble to remove a good functioning ignition system do I even need to use the ballast resistor or the coil for a bench test? That is the only point I really still need to clarify.

Thanks maybe this thread will finally clear up any foggy notions for the other short bus IH folks out there.

 

[Michael Mayben]

If you are going to actually fire a coil of the proper matching primary resistance factor for the unilite unit, then yes, the test circuit must incorporate the ballast resistor. Just like it would be installed on any vehicle.

And a complete test of the "system" on the bench would replicate the actual install on the motor. The coil must have a spark plug installed in the secondary to "load" the system and it must be grounded back to a bench battery to do this. Spin the distributor with a variable speed drill motor.

That's called a redneck distributor machine.

 

[Erik VanRenselaar]

I know there's quite a bit of *info* out there on fried unilite modules... That's why I carry a spare, and installed the active power filter, but...

I've been running the 47 series unilite on my Scout since about 1998-ish, with nary a problem. Steve: I have the advance kit/keys if you really want to play around with it. The only mod I did to mine after installation, was to back off on the vacuum advance diaphragm a bit (small hex key through the vac nipple - I wrote the size on the vac can), to decrease the amount of total vac advance. This helped eliminate any pinging while pulling a load up a steep grade. Other than that, the standard *quick and steep* centrifugal advance really seems to perk up the sv engine from off-idle and up to the c. 2500 rpm cruising range.

 

[Rusty Scout]

What is the best shim material for correcting endplay by .010"? Are these shims to be obtained from mallory? Should I call on my buddy at the transmission shop for a proper shim? Thanks

 

[Dealbreaker74]

I don't think I'm violating any rules by suggesting mcmaster-carr. This is what I found in about 1 minute, so I'm sure there is something here that will work. Order one of their catalogs while you're at it. You'll wonder how you ever bee-bopped through life without it.

mcmaster-carr

 

[Michael Mayben]

what is the best shim material for correcting endplay by .010"? Are these shims to be obtained from mallory? Should I call on my buddy at the transmission shop for a proper shim? Thanks

The shims used for setting endplay should be a typical hardened item as used in many transmissions, electric motors, etc. Do not use the typical brass shim found in hardware assortments.

Msd sells distributor shims in sets of assorted values. Some "appear" to be brass but I assure you they are not. They have surface finish color to denote thickness when used on the assembly line.