1985 Corvette

I may have found a deal on a 6AL box and was wondering what those of you with more than stock output feel about using one. I'm just running a stock distributor now on a 383 roller motor. Wondering what all would be involved incorporating it into working with stock hei. I believe the model number on this one was 6420 and used rev limiter chips externally.

DanielRicany

I have a 6AL2. Mine doesn't have "chips" but it uses a dial that you can set the RPM that you want it to limit revs at. I have another MSD RPM Activated switch for nitrous that takes the "chips" and those can be pretty expensive for what they are. $35 for a set of them and it only has like 5 different RPMs with each set.

Aside from that, MSD ignition boxes can run wider spark plug gaps because it is a capacitive discharge ignition. I would not recommend using it with a high powered coil or another CDI ignition module. I ran mine with a D.U.I. Distributor and had problems with the center post melting in the distributor cap. I'd recommend purchasing an MSD low resistance bushing as well for your application.

Mine is a 1985 and I am using the stock distributor with my MSD 6AL2. Some say that the MSD 6 series will increase gas mileage by 1-2 mpg because it has "Multiple Spark Discharge" (hence the name MSD). I'm not sure how true that is. I don't think I noticed a difference in gas mileage.

If you are using a Miniram, Holley Stealth Ram, Accel Super Ram, or carb set up, I would seriously recommend a 6AL or 6AL2 so you do not over rev the engine. I have mine set at 6200 RPMs and my stock 1985 bottom end with 108k miles has held up fine so far. I could probably set it even higher if I wanted but I wouldn't go further than 6500. I also have the valve springs required to handle 6200 RPMs.

Good luck. It's really a great product.

vader86

Unless your engine is built to run and make power at high rpm, I do not see the need. My 398 SR engine doesn't need it, but if I were running a MR or HSR I would give it some more thought.

aklim

I ran it and didn't see any mileage improvement nor did my quarter mile times get any better. So unless we do a dyno and prove something, I would say it does nothing FOR ME. YMMV

On some forums, they call it "My Spark Died"

aklim

I'll bite. Why? I haven't tested it on my HSR. What can I look forward to?

DanielRicany

Funny. I didn't notice a difference either.

The selling point is the rev limiter.

856SPEED

Had one on my minirammed 85....lasted a couple of years....no change in fuel mileage or performance.

Did a good job making my wallet lighter ....especially when I had it towed when she quit right after the warranty expired....

Some love it; wasn't a good experience for me....

383vett

I've been running a 6AL for years. Started with the removable chip model and now have the digital model with the dials. The car has gone through so many changes I can't give you a before or after comparison. For a while I switched to an aftermarket distributor but the times seemed to fall off so I'm using my 36 year old distributor today. I shift at 6600 rpm, make 200 runs/year and am happy with the MSD.

1985 Corvette

A lot of good replies pretty quick on this one. Mileage increases weren't a concern. One thing I was interested in was reduced cranking time. The 383 is a miniram 11:1 combo, comp cams xfi shelf grind 230/236. Nothing too wild but figured I was in the ballpark for an ignition "upgrade".

383vett

I'm running a miniram with 12.5 compression. I just changed starters from my old 12 year old Hitachi model to a MSD starter. That thing spins at least twice as fast!

DanielRicany

I think youre cranking time is mostly going to come down to the amount of fuel being injected during cranking. You can change that in the tune. I have a pretty decent cranking table for my set up. In very cold weather it starts and idles low the first few seconds then idles normal because it's not 100%. But I figured as long as I can get it to turn on and not stall out that's all that matters. I can post it for you if you like.

856SPEED

It also has to do with timing ....is it advanced?

blackozvet

Im using the Mallory 6a which is exactly the same as the digital MSD 6A series.
(Mallory is owned by MSD)

some people will say "does it show a difference on the dyno ?" these units only give multiple spark up to 3000 rpm, then revert to single spark. They are not designed to make more power on the dyno at high rpm. They will 'ensure' a strong single spark at the higher rpm range. The main benefit is in the 500 - 3000 rpm range.

After fitting mine and making no other changes the car ran 3 tenths quicker consistently at the hillclimb, and that is getting on and off the throttle driving out of corners. So did it work for my application - yes.

Do they play up - yes, mine has a random cut out while cold, got no idea why but I just accept it. Doesnt do it when its warmed up. a bit annoying when your half way up the trailer ramps !

If anyone is going to fit one, my big recommendation would be to use the MSD adaptor loom which is specifically made for the GM HEI, it will save you a lot of grief !
http://www.summitracing.com/int/parts/msd-8875

BOOT77

If you car is running optimal a msd will make no diff, but it can allow for better tuning(gap & fuel) and has more room for error. Several conditions make it hard to fire a plug lean, rich, compression, heat, rpm, poor grounding. HEI can be made to work well with several changes but it does not have the features of multi spark, limiter or other add-ons like retard.

cv67

save your money HEI is just fine

1985 Corvette

Been a bit since I've fooled with the timing and even then I wasn't too pleased with my efforts but I believe it was advanced from the stock 6 to 11. Sounds like the verdict is save money and stick with the HEI. That works for me! Any particular parts I can purchase to beef up the HEI such as a specific coil or module? Thanks for the feedback. It sounds like the money would be better spent reinforcing the stock ignition.

vader86

Honestly I think bone stock HEI cap/coil/rotor is just fine, I only splurge on MSD wires. I have considered the MSD coil as something to test out on a dyno to see if it smoothes out the curves at all, but since I did not appear to need it, I have not tried it.

cv67

Tried the MSD coil and rotor on an 89 it burned that little button up quickly. Put stock stuff back in and never did it again. Noticed no gain or loss with msd parts just a lighter wallet fwiw

aklim

I changed to the small cap system. Every year I change cap and rotor

cardo0

High voltage and high power is for the high compression and high rpm motors, also the power adders.

For mild rpm, compression and power stay w/HEI. It has a nice long spark. Just use a smaller 0.030" gap if going above 5,000rpm. U will want a performance unit also as the stock HEI has some short comings.