Mallory Distributor, Which one Options

[Teknon]

I called Mallory and they recommended the 4754101 but most of the threads here use the 4554101. What is the difference and why are the threads using the latter.

[Mueller]

what kind is the unit they recommended? vac, or mech. ??

[Teknon]

It's a unilite vac ad

[Teknon]

It's a unilite vac ad

[Mueller]

I have the mechanical one (uninstalled right now) since it was recommend by a few people I trust....others have installed the vac. unit and are happy with them.

the mech. unit seems pretty darn simple, the vac. unit will require more fine tuning to get it perfect

[Aaron Cox]

my mech. mallory arrived today. we'll see how it goes (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[Teknon]

This is what Mallory sent me in reply to the question.

Question: Brand: Mallory
What distributor would fit my application best between the 45,46 and 4754101 distributors and why one over the other. What are the differences between them?
Vehicle/Engine Specs:
Make: Porsche Model: 914 Year: 1975
Engine Type: 2.0L Transmission: 5sp
Modifications: Bored 2mm, stroked 7mm, dual 44mm Webers, Moderate cam and opened heads.
Discussion Topics: distributors
Solution:
45 series has centrifical advance only. 47 series has centrifical and vacuum advance. 46 series is the same as 45 series but with a mechanical tachometer drive for use with cable driven tachometers. Use the 46 series only if you have a cable driven tach. Use the 47 series if you do a lot of highway driving since vacuum advance can give you one or two miles to the gallon better highway mileage than centrifical advance alone. Otherwise, use the 45 series. RobbMc

[Jake Raby]

BUT, what they won't tell you is that if the vac unit is MUCH harder to tune AND if the vac canister dies, or the small rod that holds it pops pff it will cost you an engine as the timing absolutely dies.

I have had 3 vac units fail costing me two engines, one in a bus and one in a 914. The drivers did not notice the changes and it smoked all the exhaust valves in about 10 minutes of driving.

I live by the 4554101 and have one on every car I own, BUT the vac unit is a piece that needs more design and can cause you a failure, AND that awesome adjustability is thrown away.

In the future plan on being able to buy the Mallory 100% set up and fully optimized for the Type IV engine specifically! No one else can offer that.

I like something till it causes me a failure, then i question it. After it happens more than once I toss it from my line up. I have sent emails to all my customers that have engines outfitted with these distributors (vac advance) and have told them to replace it with the 4554101

[SGB]

I recently put the 4554 in my 2 liter, weberized car. You really need the "spring kit" to adjust the advance curve. The centrif ones (at least, maybe the vac ones too) use two springs to alter the rate of advance per rpm. The 4554 comes with an orange spring and a grey spring (actually just a little spray paint splotch on the spring), which provides a curved advance rate with advance coming on slowly and increasing continueously to the max rate allowable. The max is also adjustable. Using two grey springs proivides a straighter advance "curve", so spark is advanced earlier in the rpm range. I set mine up per Jake's advice, two grey springs, max advance at 20 degrees, and idle speed (950 to 1050) advance of 12 degrees. Judging by the curves provided with the spring kit, this achieves the fastest progreession to max advance, so that by 3000 rpm, the spark advance is at 20+12 = 32 degrees. My experience has been that, like Jake says, the power is much stronger from 3k up. I've lost a little of that first gear torque below 3k it seems, but the engine really gets eager to spin even faster as rpms increase. If you are used to Bosche behavior, you may think it is less responsive, because power is a lot more linear coming on. Jake's own dyno curves show little gain in power on his engines below 3k. The real improvement I think is not the increased power at 4 to 5 k, but the increased smoothness from the fairly low spark advance at those rpms (relative to a Bosche running over 40 degrees at these engine speeds). So you should do the spring thing before you plop it in the car. You will need a star-point screwdriver, too. I had sockets and they were not long enough to loosen the plate to adjust the max advance. It is a pretty simple set up, actually. I'm sure the optical sensor used to cost $, but that kinda stuff is cheap these days. Mallory really should have a lower cost optical one....

[Porsche Rescue]

I have heard/read gray springs and 12 and 16 for 28 degrees total advance. Which is best Jake?

[Jake Raby]

Its all dependant upon the combo. There are no standards or rules..

I can get more power below 3K, but I choose not too because if someone lugs the car below 3K and nails the throttle and leans it out it'll ping with a faster curve.

More power and more power safely for all the idiots in the world is a different thing..

You can go as high as 15 degrees initial, with 28 full with the grey springs, but I only do that with a longer rodded engine.....

[Teknon]

Looks like it's the 4554101 mech. distrib for me. Again, thank you for your expertise. Nothing outperforms true practice (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

[Porsche Rescue]

I have a stock 2.0 with webers (I believe the cam was changed to something better for carbs but I don't know the specs). I plan to order a Mallory with no vac. advance and gray springs.Where should I start? Car is used primarily for autocross.

[Jake Raby]

Wait a few weeks and you can order one already 100% set up (IMG:http://www.914world.com/bbs2/html/emoticons/boldblue.gif)

[Porsche Rescue]

Jake, will do. Let me know by PM or a post when you have one ready.

[Teknon]

How much Jake? (IMG:http://www.914world.com/bbs2/html/emoticons/lol2.gif)

[Jake Raby]

Trust me.....

Everyone will know when I am ready to sell them!

[Teknon]

How will everybody know? No price lists on your sites. Curious. (IMG:http://www.914world.com/bbs2/html/emoticons/blink.gif)