The Stovebolt Site Forums The Shop Area Engine Shop Pertronix again and again

So here I am still dickin with the TVS for supposedly protecting the Pertronix ignition.This darn diode ain't marked for polarity so....if I touch the positive lead of my Fluke meter on the left side as you see the diode in the photo and the negative on the right,the meter says 1.1 M ohms. If I reverse the leads, black on left, red on right,I get .4 M ohms.
Which end goes to the ground?
[img]http://img.villagephotos.com/p/2003-1/95040/TYOQE-tvs.jpg[/img]

Some TVS are unidirectional (one way), some are bi-directional (install either way). Get the data sheet for the part in question from mfg's website and see which it is.

Still don't know why you'd need the TVS or other protection circuitry. Doesn't the primary winding of a ign coil spike to a couple hundered volts when it fires?

I use a petronix ignitor in my 235, with a Bosch coil and ballast resistor. 12 volt conversion with the typical GM alternator and electric radiator fan and a small sunpro tach. Been running fine for about a year, including a 400 mile trip to Biloxi's Cruising the Coast last fall.

Your results may vary.....

chip

The left side is the cathode (bar part of the diode symbol), the right side is the anode (arrow part of the symbol.)

Not sure how it needs to be installed, but if the installation instructions show the symbol, install the banded end of the diode where the bar part of the symbol is.

With that said, I've never had to install a diode with a Pertronix. I've always just installed the module and the interrupter and fired it up.

Tony, the annode side goes to ground in a zener diode. The cathode end is usually identified by a band. The diode does not conduct until the zener voltage is exceeded. So at voltages less than the rated zener voltage, the device would have a high resistance to ground. I'm thinking the left side (in your photo) is the cathode.

Ah Chip, the description say "bi direct", that's why there's no marking that the other guys are talking about.The only markings on it is a logo trademark and a part number like you see in the photo.
I put a Pertronix in my 37 and 51 trucks about a month ago.A lot og guys were jabbering about voltage spikes frying the unit. I don't ,can't hurt to try these gizmos,got 20 of them for chump change,16 volt and 22 volt, 1500 watts.Anyone want one?, I'll mail it to on my stamp, but don't all line up at once.

Truckedup, you've done several hei conversions why mess with the pertronix? Anybody know what the current draw of the pertronix is; I may need one for a 24v app. I have read somewhere that the tvs are more necessary when using a generator which are apparently more apt to have voltage spikes.

The only reason you need to use them is that Pertronix cheaped out on their design and didn't adequately protect their product. The bidirectional ones can be connected either way, the closer to the unit the better. It goes in parallel, not in series.

Thanks 4 on de flo
Jason,the current draw must be very low,it's just a electronic switch.why try Pertronix? Why not I guess,lol.My 37 has has 3 different types of trannys,at least 7 carb sets ups on 2 different manifolds and a water pump conversion on it's 261 engine.All in the last 6 years since I built the truck.I enjoy trying out modifications,see what happens.
So far I'ver learned my 261 needs no more than a 390 Holley to run it's best,the water pump conversion from the low mounted 59 style pump to a 216 higher mounted pump is well worth the work. And on this engine, the HEI or the Pertronix runs exactly the same as the stock single points recurved advance distributer .On the somewhat stock 261 in my wife's 51, the Pertronix conversion is a little smoother than either the points or the HEI.All this probably depends on many variables,condition of the distributer,how well the points are adjusted, etc.I did a few HEI conversion for people, they loved em, I got tired of the big ugly cap,lol.And it's just more complication that doesn't add a thing to the performance,the simplier,the better.

Thanks for the info, truckedup. I am going to try the HEI after running the mallory for ~8 years. I have also thought about trying the pertronix in my reo 6x6 but it has a 24 volt system. Don't know if I can do it with a linear regulator mounted inside the dist or outside. Is the susceptibility to voltage spikes the main failure mode for pertronix?

Jason, yes the voltage spikes and leaving the ignition on without the engine running are the main causes of failure.I'm thinking the voltage spikes are from generators or alternators with mechanical regulators.Guys using later alternators with solid state regulation don't appear to have a problem from what I hear.
Don't take me wrong, the GM HEI is a good unit for inlines,especially if the ability to run a wide spark gap is benificial for certain siuations, like to fire off lean fuel mixtures at low speeds due to cam or carburetion tuning.
Have you checked the Petronix website? maybe they offer a 24 volt unit?

On that REO, is the 24 volts from two 12 volt batteries? Energize a 24 volt relay from the ignition switch. Connect one relay switch contact to the battery center-tap and the other relay switch contact to the Pertronix. You'll have to use a 12 volt coil.

Is that neg or pos ground?

It is two 12V batteries, negative ground. I have thought about that but most of the info on the internet frowns on center tapping to get 12V. It is said that it drains one battery more than the other preventing an even charge, etc. Hard to say if the small current draw from the ignition would matter. Pertronix doesn't list anything for 24V. But there is probably enough room inside the distributor for a TO-220 size linear regulator. And the aluminum housing will make a good heat sink. Just bought another REO this weekend. Lots of em on the surplus market.

While I was at the Milliman's this weekend,I accidently left the ignition on in my 51 for no less than 3 hours!!! When I discovered the it, i figured for sure the Pertronix was fried.That's a big NO NO, never leave the key on for more than 30 seconds without the engine running.500+ miles away from home, but I did have the points and parts in the glovebox.I sat there for a few minutes, finally I pumped the pedal,the engine started instantly, no problem at all. The battery was discharged, took an hour of running for the amp needle to settle on zero.OK, I got away with it,huh?