I bought a bunch of pefomance parts for my BB a few years ago. Project has taken a twist from a "Saturday Night" car to a semi daily driver for the wife.

Is there an advantage to installing and running the MSD 6AL with the Proform HEI? Engine is only going to spin 5600 RPM? I thing the HEI will cover it without the MSD??

 

hei good to 7k. why have 1 more headache?

 

If your stock ignition allows the engine to reach maximum RPM without misfire you don't need anything more.

 

I think someone even makes a decent hei module that fits in any hei housing with a rev limiter built in like the msd box has.

 

Real Multi spark boxes only cause additional sparking below 3000 - 3200 rpm

The 20 year old design 6AL were prone to heat failure and pretty much a POS. It's another bad product from MSD just made to make money.

 

And yet everyone has one

To the original poster NO

 

have a 6al for 6 years without 1 problem.

 

Is there an advantage? Notwithstanding other comments, yes, there can be. A piston engine will always suffer from cyclic variation. This means that conditions in the cylinder are not entirely consistent from combustion event to combustion event. One thing that does occur is sporadic and random misfire. This is usually due to a mixture vaporization anomaly. This isn't something you'd easily notice, like a consistent misfire. What a multi-sparker does is to keep hitting the plug in hopes of recovering a successful combustion event. It can give you a smoother idle.

But the 6AL is pretty dumb and the digital boxes are not much smarter. It hits the plug whether it has fired or not. And as noted above, it does this only below 3k rpm. There are other more sophisticated systems. Jacobs, before they went south of the border and started building less stellar products, did make a fairly expensive system that would send a follow up pulse to the plug to sense the ionization in the chamber and if it sensed combustion did not occur, would hit the plug again.

The other thing the 6AL (and other CD ignitions do) is instead of building the voltage rise in the coil through induction, the coil is just a transformer where the capacitor discharges into the coil where voltage is stepped up. This changes the ignition characteristics from the inductive's longer spark duration to the capactives higher rise and potential voltage. In most cases, this is really irrelevant. If you have a difficult to fire mixture, it can make a difference.

But if your engine seems to be running fine with what you have, there's not really anything to gain by going to MSD's or anyone elses box.

 

I say put it in or give it to me!

Again, wives like easy to start and evenly idling cars. Us guys don't mind a rough idle, and actually prefer it....

The MSD will idle smoother than a stock..........based on my personal experience.

 

Smoother idle may be worth the space and wiring...if not another part that's going to show up on the board for sale

 

The MSD 6AL stranded me many years ago is why I hate them. But i have a Crane digital unit and if I put a spark plug in a plug wire laying across the manifold and start my motor it almost looks like orange fuzz of a small MIG welder in action. You have to use the biggest wires on the market like 10+ mm taylor pro wires.

I did think that I had a problem with my Crane digital and I jumpered it out of the loop and I really could tell a difference in how it idled, started, or ran.

You might see something on a dyno, but not anything you can feel

 

I use the MSD 8360, HEI, no box required and it is much smaller that the GM HEI.
Works just fine

 

sounds like the msd was covering problems up on a engine that wasnt properly tuned or set up ?

 

Does that come with a tach drive? I am thinking of changing over to one of the DUI distributors since they tune it on a machine based on your engine specs.

 

I have the MSD digital 6 plus box and it isn't my imagination that it makes a huge improvement. I agree with the idle being smoother ('70 LS5,CC 280H cam, header, flowmasters, torque conv, now) as HvyMtl said, the other thing I noticed was the crispness of the motor and the launches are like a catapult. I like the timing retard at startup and the rev limiter feature it has too.

I believed that an MSD was a waste if you had a decent ignition in it beforehand, but I am a believer at this point.

To each his own.

 

I'd just use an HEI. I have the 6AL box and it has malfunctioned already and I had to send it back to MSD for $50 in repair diodes, resistors, etc. Not a costly fix but for a ZZ4 there was no reason for the previous owner to install it. If it goes bad again I'll go back to an HEI I would think- less prone to failure and good to about 7k rpm.

 

I might need that rev limiter...I see how she thrashes the C5

 

Have a 6AL for 16 years, no problem, but I only drive the car 1000 miles a year... :o

 

MSD has its place,I have had good and bad luck with them but back to your original question if your wife is not Shirley Muldowney she won't need the 6AL box.

 

I installed summits version a few weeks back. I do notice a quicker start, but I also notice that it miss fires in midrange real bad. It is to the point where it makes the car jerky, even at 55 at 3500 rpm. When I go wide open it is fine, and it don't seem to skip a beat.
The main reason I bought it was the rev limiter, I have issues with 2nd gear and don't want to scatter this new motor. I am thinking gkull was right and I now have too much juice for my 8mm accel wires. Running it in the dark tonight I could see the plugs glowing some and a pretty bright light out of my HEI where the + and- wires connect to the coil.
It also makes a racket inside the distriburtor, I heard the MSD boxes were loud, my box is quiet, but the distributor sounds like it has a mini gear drive in it!! It is a new distributor and I took it back apart and found nothing obviosly wrong.
I was impressed that it was made in the USA, I wonder if the MSD unit is.
Any other opinions on the mid range misfire?
Motor is a S/B 406 with a com 306s-10-.306--.555 solid flat tappet and has a grumpy idle anyway, but this mid range thing is new since installing the box.