The stock unit is easily good for 5000rpms. Get a good set of 8 or 8.8mm wires and you'll be ok.
Upgrading 86 HEI Distributor, Need advice
Thread Starter
Instructor
Joined: Mar 2005
Posts: 157
Likes: 2
From: Fayetteville Ga
Upgrading 86 HEI Distributor, Need advice
What would you guys recomend to upgrade the HEI coil, distributor guts, and wires on a stock 86? There are several "high output" (around 50k volt) coils and distributor upgrade kits from Mallory, MSD, Summit out there. What performs well and doesn't cause trouble with the rest of the car's electrics and sensors?
My engine is stock, just want a little more juice and it's time for a major ignition tuneup anyway.
My engine is stock, just want a little more juice and it's time for a major ignition tuneup anyway.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Large voltage numbers claimed for aftermarket coils are meaningless. What is important in ignition systems is the energy in the spark in joules. If no spark occurs, a coil can put out 50,000 or more volts, but it only takes about 5000 volts to jump a plug gap and as soon as the spark occurs, the gap voltage falls to under 100 volts and the spark is sustained until the stored energy in the magnetic field of the coil is consumed. The spark energy the coil produces is equal to 1/2 the primary current in Amps squared times the primary inductance in Henries. Increasing the current will shorten the life of the spark control module and increasing the primary inductance will cause falling energy with increasing rpm. GM made the right compromises in the HEI distributor for hot spark, long component life and no loss of spark to the limited rpm of GM engines . You can install an aftermarket ignition
system but I doubt you will see any difference.
system but I doubt you will see any difference.
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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My recommendation, just get new Delco coil and cap. I went with MSD 8.5mm wires and use Rapidfire plugs.
An L98 does not need all that juice, and with a stock intake or SR you dont really dont require the upgraded parts.
An L98 does not need all that juice, and with a stock intake or SR you dont really dont require the upgraded parts.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
I've seen it stated in several sources that the stock HEI begins to drop off in voltage above around 4,500rpm which, as mentioned, is not so bad for a stock TPI.
However, my modified TPI now pulls well to 5,800rpm so I went with the HyperTech unit that outputs 54kV and does not drop off before 5k RPM.
This also allowed me to open up the plug gap for a broader burn kernel.
However, my modified TPI now pulls well to 5,800rpm so I went with the HyperTech unit that outputs 54kV and does not drop off before 5k RPM.
This also allowed me to open up the plug gap for a broader burn kernel.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Your Hypertech coil never sees 54,000 volts because even your opened up gap plugs still only take about 5000-6000 volts to initiate a spark and when current flows across the gap the voltage drops to below 100 volts and stays there until it is extinguished. The voltage rating of a spark coil has no meaning, its only advertised to impress those who do not understand ignition systems!
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From: The Top of Utah
Originally Posted by 65Z01
However, my modified TPI now pulls well to 5,800rpm so I went with the HyperTech unit that outputs 54kV and does not drop off before 5k RPM.
RACE ON!!!
Last edited by CFI-EFI; Oct 8, 2005 at 10:44 PM. Reason: Typo
