[6567GTO]

I'm building a '65 GTO with a '73 455 & a pair of 670 heads, a close ratio M21 4 sp., and a 3.90 12 bolt posi rear. The motor has forged pistons (9.5 to 1 ) and stock reconditioned rods. It has an UltraDyne
( 288/296,110,.485"/.507",231/239 ) Hot Street/Bracket cam, a Torquer 1 Intake w/ Heat Crossover welded shut and a Holley 780 carb.
I've been piecing this car together for about 5 years now and have been buying parts throughout this time. I plan on using it as a Street/Occasional Strip, Cruise Night car. One of the parts I bought was a Mallory Mechanical Advance Unilite Distributor #3758001A. Is this a good distributor for my combination? Also I just installed a Power Disc Brake Conversion kit and plan on using a vacuum reserve canister. Will this be adequate for my brakes to operate properly? If there is anything wrong with my setup or something you think I should add? Your comments would be welcome. Thanks, Phil

[6567GTO]

I'm building a '65 GTO with a '73 455 & a pair of 670 heads, a close ratio M21 4 sp., and a 3.90 12 bolt posi rear. The motor has forged pistons (9.5 to 1 ) and stock reconditioned rods. It has an UltraDyne
( 288/296,110,.485"/.507",231/239 ) Hot Street/Bracket cam, a Torquer 1 Intake w/ Heat Crossover welded shut and a Holley 780 carb.
I've been piecing this car together for about 5 years now and have been buying parts throughout this time. I plan on using it as a Street/Occasional Strip, Cruise Night car. One of the parts I bought was a Mallory Mechanical Advance Unilite Distributor #3758001A. Is this a good distributor for my combination? Also I just installed a Power Disc Brake Conversion kit and plan on using a vacuum reserve canister. Will this be adequate for my brakes to operate properly? If there is anything wrong with my setup or something you think I should add? Your comments would be welcome. Thanks, Phil

[PROBRD]

That's a nice distributor. It should work well with your combo. With the vacuum canister you won't have a problem with the power brakes.

[KS circutguy]

When selling Speed parts at Auto Finishers Speed and Custom in the early 80's the only dist. that we had CONSTANT returns on was the Mallorys..

Save yer self some grief,buy an MSD its bullet proof and its extremely reliable in any street or racing application...

I also have lots of friends that race here in Wa. now and they too have made the switch to an MSD setup and Distributer.......

Thats my 2 cents....
KS out.

[This message has been edited by KS circutguy (edited 12-12-2000).]

[Black 65 GTO]

6567GTO,

I have been using a Mallory Unilite 4758001 (w/ Vac Advance) for about two years. No problems whatsoever. Just as a precaution: if working on your car (anything electrical, welding, etc.), ALWAYS unplug the three wire quick connect on the distributor. It will prevent any possible damage to the module. The Unilite has worked great for me.

[PONTIAC DUDE]

Be very careful of the voltage to the unit. I don't know why they recommend 9V. Maybe to sell the He** out of replacement photocells. I seem to sell more replacement parts for Mallory Unilites then all others combined. You take it from there. BTW: I did run a unilite for 5 years in a BBC Chevelle drag car with no problems. I now run MSD magnetic induction units.

[68Bird]

I have been using a Mallory Unilite in my Firebird for about 2 years. As mentioned above, the voltage fried the photocell. Mallory sells a kit to change it to magnetic. Since the change, no problems. Chris

[6567GTO]

I forgot to mention that I was using a MSD 6A
prior to the "restification" and I had what I think was a Ballast Resistor (a ceramic 2 terminal piece ) that was hooked up to the coil. Is this what knocks the voltage down to 9v ? Thanks for all the responses!

[PROBRD]

I've had several cars with the Unilites and have never lost a photocell. Just make sure you use good sound wiring practices. Good grounds. Use the ballast resistor. Follow the directions precisely and you won't have a problem. I'm currently using one that looked old 8 years ago when I bought the car. I would use it especially since you already have it. If you decide not to use it drop me an e-mail and let me know what you want for it. I won't hesitate to use it.

[This message has been edited by PROBRD (edited 12-12-2000).]

[68Bird]

PROBRD is right. I lost my photocell from not following good grounding practices as well as other things. Always in a hurry, never disconnecting my distributor or even my battery while working on the engine, etc... learned it the hard way. Good luck with the Mallory, I think you will like it. Chris

[GTO Karl]

Unilites seem to work well. My experience is that when my customers have problems, it is with the wiring.

Just to clarify, the ballast resistor is not used to drop the voltage to the coil or circuitry, that is an after affect of the true purpose. The ballast resistors job is to limit the current flowing through the electronics or points, to a safe level, for the components being used. Usually, about 2 amps is the max these circuits can handle.

The ballast resistor will get hot during times of high current load at low rpm. Causing a reduction in current flow and a voltage drop due to increased resistance. As the rpm increases, the current flows for less time for each firing of the coil, causing the resistor to cool, leading to higher voltage and current, and better spark without damaging anything. Although most consider dwell a constant, it is actually a measure in degrees of the time the points(or electronics) are permiting current to flow to the coil. If you look at this as a function of time, at low speeds, the time the current is flowing is large, which can lead to a number of problems. The coil can saturate, causing a very high current spike. Also, electronic circuits can often absorb extra current or voltage, but only for a period of time, before they overheat and fail. So, the ballast resistors job is to balance the current flow over time so that nothing does overheat and fail. It trades low current and low voltage at low rpm, for high current high voltage at high rpm, all the while allowing for good spark throughout the rpm range. This is because at low speeds, there is plenty of time for the coil to charge from a lower current and voltage source, and at high speeds, you don't have much time, so you up the current and voltage, all the while, staying within the safety limits of the parts on hand.

This is why you sometimes need two resistors with high output coils. The smaller number of primary windings in a hot coil, provide less resistance to current flow, and will destroy points or electronic circuits at low rpm.

The photo cells in the circuit of a unilite are not very sensitive to input voltage. They are very robust and operate at very low current. The circuit inside has current limiting resistors built in just for that part of the circuit and will not be affected by input voltage. They are not protected from accidental shorts and the like, however. Usually, when a unilite fails, it is not the photocells, it is the switching transitors that get burned out from too much current flowing through them, or hooking up the wires wrong, or leaving the key on with the engine not running, while a photocell just happens to be in the right spot to trigger the current to start flowing to the coil. This will quickly overheat the transistors that handle this job, and the unit will fail.

The only recomend I have, is make sure the heavy grease that mallory used during the original assembly of the advance mechanism, is cleaned off. Use a light machine oil on the parts. The stock grease, when cold, inhibits the mechanism from working properly and can cause problems for tuning your vehicle for hot and cold weather.

Hope that helps

Later

GTO Karl

[Gach]

That's all I used is Mallory Unilite's, never had a problem. I've had one on my car for 4 years. I also use a Ballast Resistor. I think allot of problems came from guys with voltage regulators, if you didn't put that little dyod on the regulator, it would feed juice back. I always unplug mine when ever I'm working on anything elec. They do say that the MSD Billet dose put out more juice, don't know if it's ture or not.

[PONTIAC DUDE]

Have tried them in Circle track cars with 180 headers, and they "WON'T" work. The heat kills them. Then they refire when cooled down. Even Mallory agreed. Seems like a lot of rules just to get spark to the plugs on a basic street engine. Magnetic induction or bust. LOL