MSD necessary with an HEI?
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 3,472
Likes: 18
From: Lake Ozark, MO
MSD necessary with an HEI?
I worded this question wrong in another post and really didn't get a consensus on what to do.......
If I'm using a new Pro Comp HEI distrubutor with 50K volt coil, is there any advantage to using a MSD 6AL or the Mallory Hy-fire VI AL with this distributor (other than the built in rev limiter)? The max revs I intend to turn with the 454 is 6000.
I already have the Hy-fire bought. But can be sold to purchase mods elsewhere if truly not needed.
If I'm using a new Pro Comp HEI distrubutor with 50K volt coil, is there any advantage to using a MSD 6AL or the Mallory Hy-fire VI AL with this distributor (other than the built in rev limiter)? The max revs I intend to turn with the 454 is 6000.
I already have the Hy-fire bought. But can be sold to purchase mods elsewhere if truly not needed.
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Capacitive Discharge (like the MSD etc) are better at firing at high cylinder pressures found in race motors. High pressures caused by high compression or forced induction or nitrous.
CD is also great at firing a really rich mixture which can happen in a race car with a carb. Better run it too rich than too lean so some err on the rich side and CD helps keeping the plugs clean.
CD is actually WORSE at firing a lean mixture that you would find at cruise. That is the real reason MSD et al fire multiple times. Each strike of a CD ignition is less likely to fire a lean mixture than an inductive ignition system (stock HEI is inductive).
For a naturally aspirated ~10:1 compression and max 6K rpm a HEI is all you need.
CD is also great at firing a really rich mixture which can happen in a race car with a carb. Better run it too rich than too lean so some err on the rich side and CD helps keeping the plugs clean.
CD is actually WORSE at firing a lean mixture that you would find at cruise. That is the real reason MSD et al fire multiple times. Each strike of a CD ignition is less likely to fire a lean mixture than an inductive ignition system (stock HEI is inductive).
For a naturally aspirated ~10:1 compression and max 6K rpm a HEI is all you need.
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 3,472
Likes: 18
From: Lake Ozark, MO
My question appears to be answered. There appears to be no significant perfomance advantage other than the built in rev limiter. I had heard that you get a smoothter idle AND since I already have it bought was just going to stick it on. I can sell it and use the $$ for some tranny stuff.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Originally Posted by Hvymtlc5
I worded this question wrong in another post and really didn't get a consensus on what to do.......If I'm using a new Pro Comp HEI distrubutor with 50K volt coil, is there any advantage to using a MSD 6AL or the Mallory Hy-fire VI AL with this distributor (other than the built in rev limiter)? The max revs I intend to turn with the 454 is 6000. I already have the Hy-fire bought. But can be sold to purchase mods elsewhere if truly not needed.
Last edited by jackson; Jan 24, 2006 at 10:38 AM.
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Originally Posted by Hvymtlc5
That MSD module is the ticket - thanks!!
And always ... always ... use plenty of heat sink grease between dist base & back of module mount.
-edit- Belleville IL ... seems like I passed through/near when I was in Bethalto IL to purchase a car last year ... I also recall a big Catsup bottle water tower in a town nearby.
Last edited by jackson; Jan 24, 2006 at 04:18 PM.
Melting Slicks
Joined: Jan 2003
Posts: 2,804
Likes: 1
From: OKC Oklahoma
Originally Posted by jackson
Sell the HyFire to someone who thinks they need it ... you won't. If you're really stuck on having a rev limiter ... you can add an inline one. OR ... MSD sells a Hi-Po HEI ignition module that replaces yours ... fits in place of existing HEI module AND IT HAS AN ONBOARD REV LIMITER ... MSD P/N 83645
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
I'd like to add that many aftermarket HEI distributors advertise that they're good to up to 7500 rpm now. Pretty sure that's what mine said. The stock HEI is 40k volt IIRC, while the aftermarket ones tend to be 50k volt.
How much does that MSD module run, any ways?
How much does that MSD module run, any ways?