pertronics question...

[KAL7467]

ok I am installing a pertronics kit to replace the points in the distributor along with a flamethrower coil(the 3.0 ohm one) ...now in posts I have read some people say they leave the ballast resistor in place and others say it is best to take it out. I am aware the system may mess with my tach a bit but how accurate is a 40 year old tach anyway ...but what is the real deal on the resistor? In case it matters I replaced my alternator with a 60amp one that was supposed to go in a 280zx and made my own little plug with diode to go on the voltage regulator plug...other than that I have not changed anything else in my electrical system...any input would be greatly apreciated especially first hand knowledge...thanks in advance

[Arne]

The 3 ohm coil should be used without a ballast resistor.

[Inf]

... I am aware the system may mess with my tach a bit but how accurate is a 40 year old tach anyway ...

FWIW my tach became completely worthless after installing the Pertronix ignitor. It bounced back and forth and the position had no relation to the actual engine speed, it would just peg from left to right and sometimes float at some totally random value in between. Pretty sure I hooked it up right, followed the instructions (can't remember if it came with them, or if I read them in a thread here).

Obviously not many people have this problem. I suggest you just take a lot of good pictures before taking anything apart and make sure not to do anything permanent, so that if something does go wrong it's easier to troubleshoot.

Going back to the stock points put my tach back in order.

[soundmasterg]

FWIW my tach became completely worthless after installing the Pertronix ignitor. It bounced back and forth and the position had no relation to the actual engine speed, it would just peg from left to right and sometimes float at some totally random value in between. Pretty sure I hooked it up right, followed the instructions (can't remember if it came with them, or if I read them in a thread here).

Obviously not many people have this problem. I suggest you just take a lot of good pictures before taking anything apart and make sure not to do anything permanent, so that if something does go wrong it's easier to troubleshoot.

Going back to the stock points put my tach back in order.

I never had that problem myself. The only problems that I had were that the Pertronix burned itself out once because ti apparently ran too hot, and I blew it out myself once from hooking the wires up backwards. Other than that, it works perfectly and I get better running and better mileage.

Greg

[coop]

Sorry for sounding so lame on this subject in my older age but at one time I knew the answer to this problem. I addressed it in a technical blurb on the IZCC site. Here is my old disertation:

"Many years ago I found out that there are at least two types of tachs for the 240Z and 260Z. One type is a four wire positive trigger tach and another is a three wire negative trip tach.

The 4 wire type has one wire that sends positive voltage to the tach, one wire is for ground and the other two leads are the trigger loop, one coming and the other going. I can't say off hand exactly where these two feed to/from but they are shown in both my 72 and 73 factory manual wiring diagrams. They are also poorly pictured in these manuals. From past experience I have found that this type of tachometer is very unreliable. I have found this true in Mazdas and Datsuns.

I have found the 3 wire type of tachometer to be much more reliable and more adaptive to aftermarket modifications to the ignition system. The 3 wire type has a positive lead, a ground and a negative trip lead that runs directly from the negative terminal on the coil. Strangely, however, I have not found a Datsun wiring diagram or picture depicting this three wire tach. Has anyone out there seen one?

OK, here is what I have done with my 72 240Z. I removed my old 4 wire tach and replaced it with the three wire. I ran all new wires to the tach to assure proper circuitry. One wire from a trustworthy + supply, another to a nice ground, and the third directly to the negative lead on the coil. Here is where a problem crops up. Remember those two wires, on the 4 wire tach that formed the positive trip circuitry? Well that loop is needed to keep your car running. Apparently the primary ignition circuitry runs through this loop (weird). I had to just complete this loop and the car started right up.

I now always use a 3 wire tach. You can easily hook up a shift light to it as well as the Jacobs electronic ignition. "

Presently, my Pertronics works great with my 3 wire tach. I have no clue, however, how to run a Pertronics with a 4 wire tach which I suspect you have.

Check to see which type of tach you have before going any further. Maybe by then, you will get some other responses on this subject.

Edited November 29, 2010 by coop
clarity

[KAL7467]

Not sure which tach I have... I assume I will have to take the tach out of the dash to see

[KAL7467]

going ahead and replacing cap and rotor and plugs and wires while I am at it. What further adjustments will i need to make when this is all done such as timing and carbs? any good write ups on post tune up adjustments? thanks in advance...

Edited November 30, 2010 by KAL7467

[5thhorsemann]

FWIW my tach became completely worthless after installing the Pertronix ignitor. It bounced back and forth and the position had no relation to the actual engine speed, it would just peg from left to right and sometimes float at some totally random value in between. Pretty sure I hooked it up right, followed the instructions (can't remember if it came with them, or if I read them in a thread here).

Obviously not many people have this problem. I suggest you just take a lot of good pictures before taking anything apart and make sure not to do anything permanent, so that if something does go wrong it's easier to troubleshoot.

Going back to the stock points put my tach back in order.

Mine did that before the Pertronics install, think it might have been a coincidence?

[Inf]

Come to think of it, I do have the 4 wire tach. Back then, I read something to the effect of what coop posted, and I tracked down a 3 wire tach out of a 280Z (I think). If I remember right, that tach may have been DOA. I spent some time mucking around with the 3 wire tach insides trying to determine the problem before giving up and putting everything back to stock.

[wa5ngp]

I have the 4 wire tach on a 73 240z. These tachs are wired such that a one turn loop on the back of the tach acts like a one turn transformer. The current through the points runs up into the dash and thru that loop. So the spiking current going thru that loop inductively couples to the other side of the transformer inside the tach. This is a pretty bad design as it routes that huge noise current spike through your dash. I guess back then people didn't care about radio or other electronics interference.

I told a hot rod friend about this setup and he mentioned that the tach on the old Jags were also that way. A poor design copied apparently.

Previously I used an old capacitive discharge electronic ignition and of course the lower current through the points rendered the tach inoperative. I was able to make it work by replacing that one loop with many turns of wire to get the coupling increased. Since then I have gone to a ZX dizzy setup. I connected that same tach to the negative lead thru a 30 ohm resistor and .01 uf capacitor and grounded the other lead and it mostly works I suspect that I need to add more turns of wire since the current is even lower. If I find the right combination I will post the results.

Currently, my Z is down. I went on 60mile trip down IH35 and wouldn't you know it, the dizzy bushings gave out stranding me down there. I had it towed home, $230 ouch. I decided to do that when the mechanic I called asked me if the "check engine" light was on.

I see someone here on the thread is from Austin. I need to send you a PM as I'm in Georgetown.

I want to fix the tach but honestly, after driving this car so long I can tell when to shift from the engine noise.

have fun

Don

[Inf]

My AAA+ card has been worth its weight in gold in the years I've owned by Z. So many times I've had problems I just call them up and tell them I need a flatbed tow truck, and I am on my way for no charge out of pocket - just some cash for a tip to the driver. Gets me a discount at NAPA too (last I checked, anyway).

There's a place up in Jollyville that specializes in Z cars called the Z Clinic. I think It's changed ownership within the last few years. I couldn't tell you if that's a good or a bad thing since I've been doing all my own work since then. The previous owner knew his way around the S30 pretty well at least.