Ignition systems help

[wicky88s1975]

Wanted to more about multiple spark ignition systems. I'm stupid here. So I wanted to know pluses and minuses. and mainly why Thanks in advance. been a while since Ive been to the forum with the holidays and all

The 75 is coming along Full VBP suspension upgrades going in as well as fixing some of bubba's fixes. One day I'll figure out how to download pics on the net.

Again thanks, Jim

[Eric]

Jim,

Glad to hear things are moving along. I'm reviving this thread to see if anyone has the experience you seek.

[wicky88s1975]

Thanks, Eric, I Appreciate the assistance

[Stingray6974]

Jim, below 3,000 rpm the spark plug will fire multiple times instead of just once. They are also easier to fine tune total advance and rate of advance. Plus you can add on toys such as boost timing retard, rev limiters, dash control of timing, and rpm controlled actuators. Disadvantages are if it breaks you are without a car until the company fixes yours or sends you another one.
Your car, being a '75, already has one of the best ignitions ever made. Self contained, high output, parts readily available, and easily repaired.

Mike

[WayneLBurnham]

A functioning HEI is a good system....

Unfortunately, too many I've owned did not function well by the late date I got them, so I went ahead and replaced them.

On a 4-Wheeler (what a real bubba calls what cute little soccer Mom's call "SUV's" in these "modren times") one of those aftermarket systems lets you move nearly all the important guts of the ignition into the cab and out of the vulnerable engine bay. This is not a concern on a sportscar.

The two practical advantages they really offer are that rev limiter and in-cab timing adjustability. That latter feature is usefull on higher end applications, but also seems to need a decent knock sensor display to hear over the racket of the engine under harsh conditions.

Of course they offer the ability to use like 1" gapped plugs, 2 trillion volt sparks, such perfect combustion only O2, N2 and rose scent comes out the tail pipe, etc., but I'm more skeptical on the practical advantages of those over a good HEI for most concerns. I do like getting the "brains" out of contact with the hot engine - where the HEI module sits in contact with the distributor body.

I guess overall, I like the adjustable rev limiters most of all. It lets you be a little irresponsible with your shifts and top end. You can pay more attention to the road without worrying about floating valves from a missed shift or just going too high.

I wouldn't expect monster performance gains over HEI though.

BTW, I am using a Mallory HyFire 6 "sorta digital" (transitional model - it was on sale) on my '75. I've used MSD's 6AL's and something else.... I bought one of the Pertronix (I) for a Ford BB but haven't used it yet. Jacabs is considered the "Cadillac". All I've used work about equally, were easy to install and never had any problems.

[Jack]

Originally posted by Stingray6974
Jim, below 3,000 rpm the spark plug will fire multiple times instead of just once. They are also easier to fine tune total advance and rate of advance. Plus you can add on toys such as boost timing retard, rev limiters, dash control of timing, and rpm controlled actuators. Disadvantages are if it breaks you are without a car until the company fixes yours or sends you another one. Your car, being a '75, already has one of the best ignitions ever made. Self contained, high output, parts readily available, and easily repaired. Mike

I agree w/Mike on all counts. For most street cars they are overkill ... that $150-up better spent elsewhere. A good condition, properly performing, coil-in-cap, vacuum advance HEI is ideal for nearly all carburated street sb/BB. That said, I'm running a msd 6 ... & it is overkill.

I have / have had many msd boxes. Over the next few days/nites I'm wiring up a dual/redundant system (2 boxes, 2 coils, dual pickup distributor) for a buddy's busch car he hopes to enter first rockingham or darlington race. There's alotta multi-strike CD boxes out there. I'm no expert but AFAIK, the ones routinely used in cup-busch-craftsman truck are either msd 6 analog or crane Hi-6. Don't get me wrong ... they're good boxes but they do fail occasionally. So Mike's comment about leaving you in the lurch is absolutely correct. Hence nascar's ubiquitous dual/redundant systems.
JACK

[wicky88s1975]

Thanks guys, I'll stick with the HEI and spend the money on more usful items. Again thanks Jim