Originally Posted by Pacfanweb
I know all about it. The Large Cap upgrade isn't an "upgrade" over an HEI. That was my point. The BEST you could ever hope for with the Large Cap upgrade (team rush, although it was around long before it was called this) is to get even with an HEI.
This would be patently FALSE.
The difference and limitations in the GM HEI, and the HEI style clones will limit the spark energy the unit can handle long before the HEI can catch up with an upgraded Jeep/Motorcraft distributor.
The Jeep/Motorcraft distributor is more tuneable from the factory,
The upgraded cap/rotor design allows the cap/rotor to handle spark energies well in excess of what would destroy or ground out in an HEI,
Not to mention the RPM limitations of the HEI and it's clones.
There simply isn't enough air gap between rotor and 'Ground' since the rotor sits right on top of the distributor shaft in an HEI, so the rotor can't handle the spark energy even close to what the upgraded Jeep/Motorcraft distributor will handle.
There is a reason places like MSD uses a 'Blow Proof' rotor and a Ford style cap instead of the HEI design rotor and cap, and that is because it simply can't handle the spark energies produced by the MSD modules, or any other well tuned maximum output electronic ignition system.
It basically makes the Duraspark system into what the HEI already is.
Again, not correct at all.
This allows you to SURPASS the HEI capabilities quite easily, And don't forget,
The Jeep/Motorcraft distributor is more tuneable from the factory, no special or replacement parts to buy to tune it,
And it is more durable and longer lasting because of it's design than the HEI and clones...
Larger cap, so you can increase your plug gap, better spark plug wire connections, etc. And if you take the "upgrade" all the way, it has you replacing the Duraspark module and wiring in an HEI module.
Again, misunderstood... and mis-informing people...
The larger cap is to space terminals apart for higher spark energies.
Ford did this with it's basic electronic ignition,
While Jeep decided to stay with the smaller cap used on breaker point ignitions.
This was a short coming from AMC/Jeep, not the Motorcraft distributor, which came with the taller/larger cap when introduced in 'Ford' vehicles...
Now, you simply apply basic common sense here...
The larger the gap between rotor and 'Ground' of the distributor shaft/base, the more spark energy you can pump through the rotor to the plugs...
HEI rotor sits right on top of the distributor shaft, so it blows through or goes around the rotor to the 'Ground' the shaft and advance weights present well before the spark energy will jump from the rotor to the 'Ground' inside the Jeep/Motorcraft with proper rotor/cap upgrade.
If you follow the 'Upgrade' all the way out, and understand WHY you are doing it,
You simply upgrade the cap, rotor & plug wires so they will handle the 600% to 1,000% more spark energy an MSD CDI module will produce!
You don't use a GM HEI module.
The GM HEI module replacement is a 'Scab In' for people that can't find a reliable 'DuraSpark' replacement anymore since 'Ford' (Motorcraft) doesn't make the DuraSpark module and you can't find one that doesn't come from 'China' or someplace like...
You could find a reasonable copy/replacement of the DuraSpark module, it would, like it always has, produce more spark energy than the HEI module does...
The HEI module replacement is simply a $25 replacement for a no longer available DuraSpark module that will live.
It's not an 'Upgrade' other than it's reasonably reliable, it's a move sideways for reliability,
But if you did the proper 'TeamRush Upgrade' all the way to the end, you would have an MSD CDI module making 600% to 1,000% more spark energy than the HEI or HEI clones...
And if you already had a Duraspark system, this might make sense, but since you need the whole mess replaced anyway, it doesn't.
This too is a misleading statment...
You want to MAXIMIZE the spark energy you can get to your spark plugs,
Then get with the program and use the distributor cap, rotor, plug wires, ect. that will produce and transmit that spark energy.
A GM HEI or HEI Clone simply WILL NOT do that because of the rotor on the shaft limitation alone.
Around 50,000 volts, the air around the rotor is going to ionize, and the spark is going to bypass or blast through the rotor to 'Ground' at the shaft, and there is NOTHING you can do about it...
So when you see the "50,000 VOLTS!" coils advertised, keep that in mind.
There is much more to spark energy than 'Voltage' and ANY FACTORY COIL CAN PRODUCE 50,000 volts with no problems...
The 'Trick' is getting that spark energy to the spark plugs, which GM HEI/HEI Clones simply can't do...
The HEI is of similar cost, and MUCH easier to do, and easier to tune once it's in there.
Similar cost, but not similar results.
If you want something that is 'EASY', as in you are simple and lazy, then HEI is your way to go.
If you want something that is MODULAR so it's UPGRADEABLE IN THE FUTURE, and you can use better parts as they become available, then the Modular Motorcraft ignition is the way to go.
Remember, there have been NUMEROUS upgrades for the 'Ford/Motorcraft' ignition since it was introduced in 1975,
But you are still stuck with the same parts, now made in 'China', for the GM HEI since 1974... And it still doesn't work particularly well, the only thing you can say for it is... It's better than breaker points, and it's 'Easy' to hook up...
You only tune the ignition ONCE to the tire size, final drive ratio, type of driving you do, ect.
So taking an extra 10 minutes to get the tune right for the next 50,000 or more miles isn't an issue...
Remember, the vacuum advance, centrifugal advance, ect are all tuneable from the factory with Jeep/Motorcraft distributor...
While you have to replace the GM HEI vacuum canister if you want an adjustable one (around $35), and you have to pull the distributor shaft, take it to a machine shop and have the centrifugal advance slots machined out or welded up if you want to change centrifugal advance...
Centrifugal TIMING can be changed the same way on both distributors, they even use the same spring sets, so the RATE can be changed, but only the Jeep/Motorcraft comes from the factory with adjustable centrifugal advance.
(and those advance weights aren't under the rotor acting like a huge 'Ground' attracting your spark energy!)
Plus the whole parts available anywhere is a nice benefit.
But to each his own.
Yup, to each his own, just give the correct and truthful information...
If you have a mild I-6 engine and for some reason the ignition is missing,
Or you want to switch from breaker points, Prestolite or some other failing system,
Then by all means, an HEI or HEI Clone is cheap, 'Easy', and you will probably not find the failings in that particular design.
You are never going to rev an I-6 to 5,000 RPM (or above) and hold it there,
So the HEI will not melt down or fail you at 2,500-3,500 RPM in an I-6 engine.
If you are trying for maximum fuel mileage,
Maximum ignition power,
Or have a V-8 engine that WILL see the 'Up' side of 4,000 RPM,
Then I would suggest an ignition that will support that V-8, or get that fuel lit for mileage, ect.
Like I've said for 40 years, the Motorcraft distributor is the best kept secret in racing!
Since you have one stock in most cases, no sense in NOT taking advantage of it,
And since the upgraded cap, rotor, plug wires don't cost you any more than the factory AMC/Jeep crap parts when you tune up,
The upgrade costs you ZERO DOLLARS over a proper tune up, which most of us need anyway...
While the HEI/Clone will cost you $300 for a 'Safe' version...