Mallory 3838701 TachDrive Unilite Distributor & 312


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By elchromeo - 14 Years Ago
New to the Y Block world somewhat, I am just opening up a 56 312 in a 56 T-Bird that has had the the Carb and Dizzy plague for year with my inlaws, car is now my wife's and it was her mother from new so I need it to be dependable restoring to a driver car to USE. I thought I would go with the Mallory Tach drive unilite and change the intake to a 57 ECZ9245B and use a 4160 465Cfm Holley to hopefully make this engine come back to life along with just needing to be gone though anyway has two low holes and no rear main left.

Big part of my question is there is no vacuum advance on the new Mallory Unilite electronic Ign. with the mechanical Tach drive, not being from the electronic ignition world, how will this work with the stock 312 and Holley on the low end and actually in general for performance with this unit in a normal driver and interstate car, School me please on the install and operation of this Unlite.



Thanks guys
By GREENBIRD56 - 14 Years Ago
Free advice is what you make of it - and sometimes only worth what you paid for it!

I'm assuming you are using the Unilite to keep the tach drive - and giving up the vacuum advance for that reason. Having no vacuum advance will limit your gas mileage  - but the engine will be happy enough. Set up the spark advance before you start tuning the carb.

A stocker bird engine with original heads and a carb can use 36 -38 degrees of total advance. With no live vacuum advance - I'd set the initial at 14 degrees. So the dizzy must be set-up to provide 6-7 degrees distributor / 12-14 crank degrees. Get some directions for the distributor so you'll know how to set the internal advance stops - and learn how to change the advance springs to control the "curve". The springs should put all of the advance in by 3000 rpm at the very most - and I'd be trying some quicker springs if that will work without pinging. Finding someone with an old fashioned SUN distributor machine can take the pain out of this.

Get as "hot" a coil as the manufacturer recommends and decent low ohm spark plug wires.

You'll find a number of old threads on here about tuning the Holley carb, so look one up - be sure you get the idle transfer set-up right and you will like the results.

Good luck!

By Hoosier Hurricane - 14 Years Ago
Steve:

Please review your math.  14 initial and 14 crank degrees advance does not equal the desired 38.

By GREENBIRD56 - 14 Years Ago
I've been reading legal papers for three days and my brain is fried......as I said advice is cheap....Smile

Lets see..... 38°(total) - 14°(initial) ÷ 2 = 12°  yup! so the dizzy needs 11°-12° at the internal stops..... I don't know if info is available for that model of distributor online - but it would be worth looking for.

Thanks Hoosier - its nice to be working with a net! I am not paying the proper attention to the things that count.

When engineering tech terms get converted to "legalese" (ad infinitum) - and then wrangled around for use at the patent office - its like reading the King James version of the space shuttle landing manual............w00tw00tw00t 

By elchromeo - 14 Years Ago
Thank You for the info will follow and look up the holley treads,





Q Is there a need to use a Ballast on the hot side of the stock Resister or can one of the other be use as a singe before the coil.
By GREENBIRD56 - 14 Years Ago
You will only need one ballast resistor at the most - and which one you use (or none at all) will depend on how many amps the distributor manufacturer says it can switch.

The ballast resistor is used to protect the coil or the switching mechanism (points or transistor) or both.

Some of the newer outfits have temp resistant coils - and high amp switch mechanisms to go along with them. They will run on full battery voltage and 6 or 7 amps current. Its best to check out what the dizzy manufacturer recommends.  

By elchromeo - 14 Years Ago
Ok, I have done the research and of corse Mallory suggests their #700 ballast or the equal to there specs. I have no problem with that and putting in place of the 56 year old factory resister. Just double checking myself on leaving the old one and putting the new recommended one before it, so will run one new one

Plug wire Question, I have on now a fairly new set a 312 pre fit correct wires that are "high temp static suppression 7mm" wire. I not 100% sure of the core but I would think there are a copper/stainless twisted core, not a fiber core that is the best for Electronic Ing. In this stock engine I would think they will carry things just fine or at a high percentage of this engines performance ability?? what is your take on that!
By GREENBIRD56 - 14 Years Ago
If you already have the wire coil wrapped - "magnetic suppression" wire (sounds like you do) - use it. Its the best choice for this sort of system anyway.

The old graphite filled antique suppression stuff isn't going to work too well and the new electronic switching units hate straight solid core wire.

I believe the Mallory ballast resistor you mentioned is a "variable resistance" type - when it is cold, it lowers the resistance to give a hot starting spark - then warms up to its normal value after the engine runs awhile. Anyway - it usually bench tests at a low cold value. 

I checked out the Mallory web site - the #700 ballast resistor is .75 OHMs cold and 1.50 OHMs hot - so they are basically suggesting you not use anything less than a 1.50 OHM resistor.

The coil they suggest for the Unilite system is a # 29216 (or #29220) which are .7 OHMs primary resistance. So total with ballast is 1.45 OHMs cold and 2.2 OHMs hot.

The info also suggests that the Unilites with part numbers ending in "01" come with a total centrifugal advance of 24°. So I would set the initial at 12°-13° and see how that works. If the final advance point turns out to be way upstairs RPM wise - look into the Mallory advance modification kit #29015.