I have been considering different options for an ignition box and I believe I would be best served with a Mallory 685, in part because it also contains a built-in window switch.

Now please understand...
The last time I was into nitrous there WAS no fancy electronic stuff. You just turned your distributor to retard the timing. MAYBE, if you were fancy, you had your distributor recurved. Other than that, you just cranked open the bottle by hand, flipped up the arming switch that you probably hid in the ashtray and used a push-button momentary switch to control nitrous flow.

All this new-fnagled electronic stuff is new to me.

SO HERE'S WHAT I'M LOOKING FOR:

In choosing the Mallory 685, is there anything I am not taking into consideration, perhaps because I don't know any better?

Also, there seem to be multiple versions of the 685, but even Mallory's website isn't 100% clear on the differences.


If someone can offer me some guidance on this, I'd appreciate it.

 

I just ordered the Mallory 685 HyFire multistrike for $220 shipped. It is as you described. You don't want the 685xM series as these do not have the full length of features and are lower priced.

If you are wondering about how the window switch, rev limiter and timing retard works then I will let you know the specifics when the order arrives. It should be within days. I'm going to step out and tell you how I "think" these triggers work with a nitrous system. If I'm wrong, I will correct the information as it shakes out. Also, I'm hoping we will get some real answers by experienced users.

The window switch is a connection that can be used to run between the nitrous switch and a ground or power source with the mallory box in between. If we set the switch to open (break connection) below 3000 rpm then the nitrous solenoid will drop or stay closed even though the nitrous switch is in connect mode. Once the Mallory gets the arbitrary signal from the PCM, the connection is made within the mallory box and nitrous solenoid(s) can be powered to open and nitrous flows. The same thing occurs in reverse when the user programmed maximum rpm is detected from the PCM.

The rev limiter is different in that it inhibits spark on intervals when the Mallory detects that the user set rpm limit has been reached (boolean logic). There is internal intelligence in this as the Mallory knows the cycle of spark inhibiting it takes to drop one cylinder at a time from the spark supply.

Timing control is done in a similar fashion but of course no spark is withheld. In other words delayed (for timing retard) for the tiny increments it takes to satisfy the user's preset control. In order for this to work at the proper time, such as when the nitrous is flowing, the Mallory has to see that the nitrous switch is closed (in contact). Whether this is done in tandem with the window switch or there is other wiring involved to "see" connections is a matter to be discovered when I actually get the instruction manual or if someone with real experience tells us how it works.

You can take my inexperienced explanation with a grain of salt as I am just going by what is anticipated. If I'm wrong on any of these points, I hope someone will tactfully correct me. Once again, what I have written is merely how I think it all works. Sorry about the lengthy post.

 

There are options to the Mallory or MSD for nitrous control. If you go the Harris Speed Works for example, there are controls that do not incorporate an ignition box. The HEI supplied with the LT1 is a very effective ignition.

Go here to see what options there are to the Mallory or MSD etc.

http://www.harrisspeedworks.com/shop/home.php?cat=338