[beemergary]

HELP Put a mallory hyfire 6al in poncho. In dash tach doesn't work. MSD didital tach and shift light does. Bought 29074 tach adapter from mallory, now car doesn't run with it hooked up. Hard to understand instructions but I think I got it right. HELP HELP Thanks

[george kujanski]

If the Mallory Hyfire is the same type as the MSD 6al, the OEM tachs wonk work using the OEM connections. The MSD has a tach output that the OEM tach should be connected to. if the Mallory has a tach output also, you should use it with the OEM tach.

george

[beemergary]

It does have a tach wire, The tack trigger wire no longer comes from the negative side of coil but the box. My understanding is oem and other brands can't get enough power so the adapter does this. May have to call mallory and be on hold forever. Thanks

[johnta1]

I thought 6AL was a MSD product?

Is it a Mallory or MSD box?

[johnta1]

Never mind.
I looked up Mallory. It's VI AL

I would take the adapter off.

The only wires to the coil are orange and small black right?

Try connecting your tachometer trigger wire to the yellow wire of the
HYFIRE and see if that works.

[beemergary]

Got a hold of Mallory today. I hooked everthing up right. There's some oem style tachs that just won't work with there or msd, crane, jacobs, etc. boxes. You buy these things but they don't tell you this. Well I told them of one and the guy in tech tells me of others. I can live without there box but not my correct in dash tach. Found some tach repair and restoration places that know about the problem and can make a conversion for around $200.00 Another costly car related mistake. IF ITS GOT **** OR TIRES ITS GOIN TO GIVE YOU TROUBLE

[Peter Serio]

The original poster never does state what year or model Pontiac he is working on but keep in mind that the original "single terminal" one wire; factory tachometers from the 1960s were all designed to operate off of the stock points type ignition system only!

A vintage points type tachometer out of a 64, thru 71 GTO will not operate off of any modern, aftermarket electronic or transistor ignition distributor upgrade kit.


The circuit board to de-code a modern or transistor ignition RPM singal is completely different than the simple points type circuit board that 98% of the cars had if it came from the factory with a tach option. If you want to send me your tach I can build you the proper board & calibrate it for you. I will do it for less than $200.

Pete

[MARINA 66]

gREAT TOPIC AS i AM IN THE MIDDLE OF WIRINing my '66 Lemans with Ron Francis Wiring, 6AL Box and MSD Dist w/blaster coil. My question: My car didn't originally have a tach. I replaced the guages with rally guages. I cannot figure out from my diagrams, how the 2 big leads off the bottom of the tach should be wired. the tach came with a small wire mounted to a small stud near the top, which I assume is the original type feed that would have gone to the negative coil wire. Can I put that wire into the tach output on the 6AL, and how do I wire the bottom 2 large flat leads? The leads are set at an angle designed to take a factory type plug. your help greatly appreciated.

[Peter Serio]

The info I have on modern MSD boxes is that the white wire out of the Electronic amplifier box carries your engine's RPM signal. Wiring is as follows: The tach gets it's ground from the metal enclosure that it is mounted in. (The housing needs to be wired to chassis ground.) The yellow arrow calls out the location term. which you need to route your white wire to from your MSD Amp Box. The 2 long studs NEED to be isolated from the metal enclosure!!!!!, only reason I mention this is last week I bought some assorted sets of used rally gauges for parts. Damn good thing I decided to tear down the sets prior to testing the tachs. One set; the inner insulators were BOTH missing off of the long studs, BUT the outer ones where there; AND any test would have been an instant direct short to ground!!!!

[MARINA 66]

You'll see that I posted this message so that it would end up on front page. Don't bother responding to it, this is terrific info. The pictures are perfect. I bought the replacement Rally gauges from Ames. The back configuration looks different but it seems to be in the same general layout. I'll wire it as you suggest. It will be a few weeks before I know anything as I'm still waiting on the radiator and havent installed the intake and fuel lines. Thanks again for the help, much appreciated.

[racerboy]

Originally Posted by Peter Serio

The info I have on modern MSD boxes is that the white wire out of the Electronic amplifier box carries your engine's RPM signal. Wiring is as follows: The tach gets it's ground from the metal enclosure that it is mounted in. (The housing needs to be wired to chassis ground.) The yellow arrow calls out the location term. which you need to route your white wire to from your MSD Amp Box. The 2 long studs NEED to be isolated from the metal enclosure!!!!!, only reason I mention this is last week I bought some assorted sets of used rally gauges for parts. Damn good thing I decided to tear down the sets prior to testing the tachs. One set; the inner insulators were BOTH missing off of the long studs, BUT the outer ones where there; AND any test would have been an instant direct short to ground!!!!

Pete-
I'm trying to get my factory tach to work with my MSD-6AL. In your photo above, you show two spade terminals, one marked '12V' and the other marked 'coil'. My '67 tach only has one spade, the one you marked as '12V', where the wire ran to the negative side of coil. Does this still get connected to anything oonce the MSD white wire goes to the side you marked as 'coil'?

Also. it looks like mine only has an insulator on the '12V' terminal. Soes this mean I need one on the other?

[llucas]

Peter Serio, if you can change the circuit board and re-cal the tach why don't you just whip up an outboard wave shaping circuit that will take the modern coil waveform and put out an approximation of the points-type waveform?