MSD Decision

[PatricksDad]

Is there any reason not to upgrade to a digital 7 programmable box from a 6-AL?

I've a buddy that's finishing up a moderately stout big-inch Chevy and we have a chance to trade even up from the 6 to the programmable 7. No need for any of the advanced features (yet), just wondering if there's a downside.

[squirrel]

Cost is the big downside. If you don't have to deal with that....go for it.

[JeffMcKC]

Which dig 7 box, if it does not have launch retard I would not bother I dont think.

[PatricksDad]

It's the full-house digital programmable 7 plus.

The reason I ask this question at all is that is seems that the 7 will provide a hotter spark. If that's not the case, there's not much reason to switch for a NA carbureted mill.

[JeffMcKC]

I ask the same question a Dig 7 Plus can be bought without launch retard ( they dont allow it in some classes) just list the number like a 7520 has no launch retard but is a dig 7 plus.


Nascar can make 860 hp with a 6 just sayin

[squirrel]

get it and I'll trade you a 6A box for it, straight across.

[PatricksDad]

Both already live in the same garage. KISS principle says use the 6-AL.

[Barry Donovan]

programmable is to bridge vacuum to boost..never easy.
n/a has been mastered since points and centrifigual weights.

a large carb could use a few degrees beyond for starting...big engines could care less.

I was going 5520, it won't fit in my midget car anywhere safe. (I need to design as if 3 feet of water is over the hood).

when the ignition is really good, alt gets jumpy...play with engine grounds, check diagram for alternator (see where it gets "battery negative").

bam. instant nice.

I have not blamed a box yet for anything.

[JeffMcKC]

HUH?

[Caveman Tony]

apparently, Barry has been into the catnip again...

[Caveman Tony]

Lemme give it a whirl... this time I'll really concentrate:

programmable is to bridge vacuum to boost..never easy.
n/a has been mastered since points and centrifigual weights.
TRANSLATE: old ignition syatems weren't that bad, but new ones are great for boost, which can be challenging for weaker ignition systems

a large carb could use a few degrees beyond for starting...big engines could care less.
TRANSLATE: bigger carbs are helped by a little advance... but larger engines don't necessarily need it

I was going 5520, it won't fit in my midget car anywhere safe. (I need to design as if 3 feet of water is over the hood).
TRANSLATE: Subaru's are small. Puddles get deep up in Maine.

when the ignition is really good, alt gets jumpy...play with engine grounds, check diagram for alternator (see where it gets "battery negative").
TRANSLATE: High power ignitions cause alternator outputs to fluctuate (exacerbated if grounds are bad?)

bam. instant nice.
TRANSLATE: Fixed

I have not blamed a box yet for anything.
TRANSLATE: A Vagina is a common target to blame for Man's eternal woes, but not so for Barry. His box works.

or did he mean the MSD box?



How'd I do?

[CDMBill]

F*ck if I know? But on the issue of how much advance big motors need? My last largesse carbed engine, a 572", wanted 20* initial to be even kinda happy. I used an MSD Digital 6 witha start retard to spin it up. The EFI'd 588 likes 26* initial/ at idle as its distributor less and all those compromises mechanical advance systems have are no longer necessary. It spins on th start with 10* initial until it hits 700 rpm.

[nesabo]

Lemme give it a whirl... this time I'll really concentrate:



or did he mean the MSD box?



How'd I do?

I think you nailed it!! However I think either one is the correct answer for the last one.

[krusty]

"Nascar can make 860 hp with a 6 just sayin" Very true, but this is with a HVC (black) box and coil, not the regular (red) 6AL box and coil. When we underwent the change (upsell) to the HVC box in Cup, my MSD rep told me it provided better spark at high rpms (we were running engines then at 9400+ down the longer straights on the 1 1/2 mile tand up tracks) than the red box. If you run under these circumstances, the free upgrade might be worth it. The HVC box easily supports well over 900 hp in our LSR carrunning in high gear at 8200 to 9200 rpm for three miles. The red box will probably do as well, but maybe not for such prolonged time at high rpm. vic

[PatricksDad]

Thanks for the humor and thoughtful answers.

This will be for a 550-600hp (primarily) street driven '70 Chevelle. No PA of any kind envisioned.