MSheehy

Hi there,

I’m the relatively new owner of a 1970 L-46 convertible. I drove the car for about half an hour shut it down and restarted it an hour and a half later. I let it idle for a couple of minutes and just before I was about to get underway, it stalled. I was unable to restart it and, although I suspected a fuel issue as it was 95 degrees, I started investigating and figured out that there was no spark. Replaced the coil and nothing. The car is equipped with an MSD 6AL, PN: 6420, which appears to—after conducting the test recommended by MSD—have bitten the dust on me.

I loved the way the car was running and I’m wondering what my options are as MSD doesn’t appear to make the model I have anymore. Is there a new model that will hook right into the pre-existing wiring? The car is in my employer’s parking lot and although it’s secure, I’d really like to get it home.

Best regards,
Matt

Rescue Rogers

Can you contact MSD and ask them. I have the 6Al digital but I cont know what wiring harness you have.....

Big Block Dave

They [Edit MSD 6 series boxes] all wire the same way, as in where the wires go. The 6425 would be the "upgrade" replacement for that model, but you could also use the streetfire 5520. Personally I would use the 6425.

Unless the previous owner did some fancy plug in connectors to make the 6al box somewhat "quick disconnect", you will be splicing into the wiring. The 6425 has a plug in "harness" on its body, but its wiring will have to either be spliced into what you already have, or used to replace whats there.

7t9l82

The new digital box has a plug on the end of it that actually makes it easier to change boxes but you would have to splice into the wires you have there but it should work the same. I agree I would contact MSD and ask for their direction on it

71chimera

JMO
OE Points & coil ignition works very well without an additional CD / MSD box. And, as you now know, when a CD box pukes (& they do) most drivers are stuck.

Big Block Dave

No need to really make a call... Look up the instructions for each box online and compare. They will wire up the same and you’ll have the schematic for confirmation

resdoggie

Might be a good time to step up to a 6530 programmable box if you like doing your own timing curves.

c66vet

Check to see if your getting 12V to the box. They act up and will not run.

Big2Bird

Handy.

Jebbysan

True.....the MSD will shut off at 11.9 volts.....this is important.
Another thing about the new digital 6 AL is that it has a damn power light on it......took MSD 45 years to figure that one out.

Jebby

Mrvettenick

Contact MSD. They will repair your box. They've done it for me. The trade off is if you can be without the box for a couple of weeks, Other option is ebay.

71chimera

OP
another option is to disconnect the 6 box and take it out of your ignition loop; try running car without a 6 box and see if it still suits you.

Big2Bird

This thread could be titled "Myriad reasons a MSD box will leave you stranded."
Easy to change
Send it back
Dies under 12 volts
Does nothing over 2krpm
Left me stranded
Dyno showed no hp improvement.

resdoggie

From my MSD 6530 digital box manual: "The MSD Programmable 6AL-2 Ignition Control will operate on any negative ground, 12 volt electrical
system with a distributor. The MSD can be used with 16 volt batteries and can withstand a momentary
24 volts in case of jump starts. The Ignitions will deliver full voltage with a supply of 9-18 volts and
will operate with a supply voltage as low as five volts."

What are the HEI specs for comparison?

Mrvettenick

The big difference is spark duration and spark energy. HEI drops off at 4500. BTW, how many HEI modules take a dump each year? I guess all the people running MSD must be mistaken.

71chimera

Points ignition rarely fail outright; cheap & easy to troubleshoot & repair
points or condenser or coil under $20 each locally

HEI are rather reliable & robust and they'll light a CT car beyond 6K
module or coil under $20 each locally

what's inside a 6 box that avg joe can R&R and which parts store has it & how much is it ?

I have an HVC 6 box (black-ribbed) and matching HVC coil as well as a Marine 6 box; the HVC was on a cup car and was a spare for my late model CT car;
If the carb is setup & tuned right & does Not pull gas over/go rich, then most motors don't need ignition supplement.
But, if ya really like the bling of a red-ribbed box, you can leave it there & just bypass it; nobody'll know but you.

Mrvettenick

If it's that simple, then how could MSD be in business for 45 years?

Big2Bird

Let's start with Robert Bosch in the 1890's, He invented magneto ignition. This is still used in airplanes and race cars. Top fuel, etc.
It works perfectly. The faster you go, the more spark it gives out. BUT, since it works better at high rpm, not so much starting. Impulse units are used, blah blah.
You may have a Bosch Dishwasher or power tool at home. Their logo is a magneto.

Now Kettering. They wanted something lighter, cheaper, easier, blah blah for cars. He came up with electric induction.
For the time, much cheaper, adequate.
Starts DELCO (Also joint invented FREON).
The drawback is dwell time. It has it's limits. The coil is firing 300 times a second at 4500 rpm.
Solution, dual points.
Works better, but then another wall. Duty cycle, blah blah

Solid state. Using a trigger and amplifier, you can spin higher. Still that one coil, 8 cylinder thing gets in the way.
4 cylinders don't have this issue.

TI and HEI are not the same, but work the same way.

That dam one coil thing.
Enter crank trigger/coil pack.
Problem gone.
Dwell/heat cycle solved.

Mrvettenick

MSD with one coil isn't perfect, but it's a heck of a lot better with ir than without it. Sure, multiple coils are better, but if you want the original set up.......
All of my vehicles have MSD, and I know that they run better..

71chimera

most pro circletrack & roadrace cars w/ big V8 AND that ran carbs & MSD distributors w/ MSD Boxes also ran a redundant system. Crane similar.
One dual pickup aka dual trigger distributor
Two CD boxes that're "Single Action Only" & Selectable (b1 & b2: helps when one of em pukes)
Two Coils that're also "Single Action Only" but are Automatically Selected via One MSD 8210 https://www.holley.com/products/igni...ies/parts/8210