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Old 12-23-2006, 05:08 AM
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wickedwagon767 wickedwagon767 is offline
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Distributor tech 101, AMC options

I'm getting info together to tune my 360 in order to get it running as smooth as possible for a while until I rebuild/modify it, or a 401.

My current area of concern is ignition options. I like the simplicity of the HEI units I've seen and the high voltage coils I've seen advertised for them but it seems that HEI is all I hear about. I've heard the one-wire hookup isn't as simple as people are led to believe (something about the wire not being a thick enough gage for the extra voltage). I know there has to be other options out there, besides the obvious aftermarket distributor/coil/box upgrade systems like those offered by MSD and Mallory.

I've seen Junkyard Genius get into some fairly lengthy debates on ignition and other topics and am curious to hear his perspective, and any facts he may have in comparing/contrasting the GM HEI type ignition versus any and all competition from mild to wild setups for daily drivers to full-blown beasts.
Old 12-23-2006, 06:00 AM
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billyrb billyrb is offline
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when I installed my DUI HEI system a while back, I chose to run a new, heavier gauge wire to the HEI, based on the recommendations of the manufacturer. But, then again my wiring had been hacked by the previous owner. For the wiring, it's not a big deal. Some heavy gauge wire, two ends, some solder and some heat-shrink tubing. All of about 10-15 minutes.

For the upgrade, there are a few ways you can go. There is the TFI upgrade, for around $100 bucks. There is the HEI upgrade, for around $150 to $450 depending on brand. There is also the MSD-6A ignition box upgrade too. HEI is usually the final step most folks take after they've fiddled with all the other stuff. In my opinion (for whatever that is worth), I prefer to spend the money once and just go straight to HEI, rather than do the TFI first, then the 6-a, then HEI.
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Old 12-23-2006, 07:15 AM
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fulsizjeep fulsizjeep is offline
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JYG - Sure, links are OK. Information is valuable. It is the attitude that seems to stray off course though.
Ran when parked.
88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s with a few Evil Twin & TT's Fabworks mods
76 401 Wag, 77 401 Wag, 77 401 J20
Old 12-23-2006, 07:24 AM
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fulsizjeep fulsizjeep is offline
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Please, no need to be sorry. I have an attitude some days myself. We all float our boat a little different than the next guy. Like I prefer to use Jacobs ignitions, have 3 FSJs with them and have seen people bash them, but hey - they work for me.
Ran when parked.
88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s with a few Evil Twin & TT's Fabworks mods
76 401 Wag, 77 401 Wag, 77 401 J20
Old 12-23-2006, 07:27 AM
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jeepfan93 jeepfan93 is offline
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Well done JYG. I did the TFI on all of my vehicles, and on my 91 I did the HEI module upgrade, all outlined and I believe "engineered" by you. I now know that this the last upgrade to my ignition system I will have to do. I won't be needing to go to an aftermarket system, ie, MSD etc. My truck starts so fast it's scary. Faster than my 05 Explorer with 30K miles. Power does not fall off after 4000 rpm any more, just keeps pulling until the engine doesn't have any more in it. Spent less than $100 for all of it through Advanced Auto including Accel wires and wire seperators. And best of all took less than hour to do everything. Got the reliablity of HEI module, high output ignition system that will last until god knows when.
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Old 12-23-2006, 08:21 AM
GWChris GWChris is offline
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I'll vouch for JYG's info. I'm an Electrical Engineer with 20yrs experience designing products for use in tough industrial environments. One of my buddies (was my boss for many years) worked at Ford designing the Duraspark system. The HEI design shows all of the hallmarks of serious compromises to reduce cost of parts and cost of assembly. Inside the distributor is certainly not the environment to put the electronic parts, and there isn't enough room for the coil in the cap - even when you make the cap gigantic. Looks like it was dreamed up by some Industrial Engineer to make manufactuing easier - it can be bolted on as more of a self contained assembly - and the poor guys designing it were stuck with trying to make it work.

Anyway, I still haven't gotten around to upgrading the cap/rotor/wires - mostly because the wires are expensive and it's running great as-is, and of course it always needs something else (muffler, tires, etc.). But that's where I'd start. I don't know if I'd bother with the coil, but probably if I can remember to snag one the next time I'm at the junkyard.

If you put on the later Ford cap/rotor/wires and coil, what more could you want for a street ignition system?

The only question I'm still trying to settle is that of plug gap - I figure rafter the upgrades I'll go to 0.040", but I'd like to hear more of the pros and cons of that discussion.
Old 12-23-2006, 08:48 AM
Ristow Ristow is offline
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from a technical standpoint the motorcraft ignition may very well be a better ignition,but from a user standpoint i take an HEI every time.and not because of the "one wire hookup",but because it is a better performer. i've made 2 HEI's for AMC V8's,my 401 runs very noticeably better with it,the other one i made for a friend reports the same results.

i'm not saying the m/c's are garbage either-they can certainly be made to run well,i still have the m/c in my '83,and have gotton it to run rather well,and if a guy is on a budget,i say keep the m/c and get it whipped into shape.JYG has some of the best info on getting the most from the m/c a nutshell,put the mechanical advance on the smaller slot,and dial in your vacuum advance,which will un-doubtedly be set-up way too light.however,when i get the 3rd HEI done it'll be replaced as well.

i can say that i can't remember the last time i saw a fast ford using duraspark will see them with HEI's though.
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Old 12-23-2006, 06:05 PM
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jeff45mb jeff45mb is offline
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How hard is it to make those HEI's fit the 401?
Old 12-23-2006, 06:18 PM
grimgaunt grimgaunt is offline
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Jacobs ignitions

Flint said - "Like I prefer to use Jacobs ignitions, have 3 FSJs with them and have seen people bash them, but hey - they work for me."

- OK- except when they get wet or rained on !!!

to me thats unacceptable in an off-road setup. YMMV
Old 12-23-2006, 06:48 PM
mark32725 mark32725 is offline
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Location: Florida
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I run a Mallory Unilite with no vacum advance, easy 3 mire hookup, no external modules, led triggered, seems unaffected by water going over the motor at times, and it pulls up to my motors 6,300 rpm peak with no hicups... but the price is a little higher probably than other options... oh ya and when I got it it didnt have a gear on the end or even a hole for the press pin, you have to drill it yourself, unless they have changed that over the years....
84 Grand Wagoneer, 440/727/205, trimmed fenders, altered wheelbase, Dana 60HP Front, Dana 70 Rear, 37" Boggers, and Hydraulic winch
Old 12-23-2006, 08:17 PM
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nograin nograin is offline
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Great info there JYG and Billy.
FWIW, here's a thread I posted way back with some coil outout numbers I got from MSD.
not sure if my spelling was really that bad or something got mucked in the forum upgrades, anyway.....

As far as the initial question. My take is
Stock is almost always the Simplest answer.
That can certainly be true in this case. IF all the components are in good condition, and the engine and especially the cam are stock, it will run smooth. One thing that frequently happens during upgrades is that the components replaced were worn out. Of course it runs 100 times better! (On my website, I've posted measured resistances of a few brands of ignition wires which can give you a sense of what is out there)

Now if you don't mind doing a little modification, then go ahead and upgrade. There's nothing complicated about the TFI wiring, so I really don't see that as more complicated than the HEI single wire. In fact, it seems simpler to me since its only a change in the type of connector on the coil. The only slight but real challenge is mounting the TFI coil.

As far as opening up the spark plug gap, that seems to be the ultimate goal of upgrading an ignition system. If the system can produce enough voltage to make the initial jump in all conditions, then opening the gap will produce a better initial kernel and more thoroughly and smoothly ignite the mix. If this is really significant, then its possible timing will have to be reduced slightly.

This is what normally is recommended with an MSD 6 system. That is, open up the gap to 0.045 + and reduce the timing curve 2-3 degrees. Obviously any decent cap discharge system with good wires etc etc will have both the voltage to make the wider jump and the current to produce a good spark. Some say that the Autotronics system isn't that great at low rpm, and that is why they have multi-spark. It does seem like the Blaster 2 is optimized for higher rpm, but considering their target market, this all works out very well. The multi spark helps overcome misfires at low rpm due to high overlap cams, and then works more efficiently as the cam builds into its power band.
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Last edited by nograin : 12-23-2006 at 10:33 PM.
Old 12-23-2006, 09:48 PM
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rreed rreed is offline
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The HEI module you guys speak of, is that the TFI/HEI hybrid setup? Jeeps Unlimited CJ forum I frequent talks about it often, lots of writeups, everyone seems to indicate it is the best way to go. Same as here HEI vs. TFI is a religuious discussion but everyone agrees there that the hybrid is best. I forget the details but a four-connector HEI module is wired in, attached to a large heat sink via Radio Shack, bolted/thoroughly grounded to something, use 10 ga. wire for everything, and off you go.
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Old 12-24-2006, 11:04 AM
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DieselSJ DieselSJ is offline
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My experience with HEI...

I have been involved with cars my whole life, and have been directly involved in racing (land speed, IMSA, off-road, Pike's Peak and a couple others) since 1985. I can tell you that I have never seen a competitive team use HEI for anything - they are too unreliable. If HEI is so good, then why did GM kill it off in the late 80's? Because there are much better (and less expensive) options out there.

We have a '72 SS El Camino. Stock dizzy used points. Well, some parts guy told Dad that HEI was great so he bought one. Two years later, after burning up 2 coils and 3 ignition modules, I got tired of getting the emergency calls to tow him home and bought a MSD dizzy and 6A box and coil. The car has never run better, and we are pushing 6 years without an ignition problem.

Also had similar issues on my CJ. I used a HEI when I did the engine swap because the 4cyl that I pulled out had a HEI dizzy (which had killed a coil and 2 ign modules in about 40K miles) and someone gave me a brand new HEI dizzy. Again, failed coils, failed ignition modules, and performance issues over 3000rpm. I always carried an extra module and coil and the tools to change them, and on more than one occasion I was on the side of the trail changing parts. I finally got tired of all that and installed a MSD dizzy, but I went a slightly different route. I didn't want to use a 6A box, so I am using the pickup in the dizzy to trigger an external GM ign module (from early 90's Camaro) and I'm using an e-core style coil. That has performed flawlessly for about 5 years now.

The HEI module was designed around 1970's technology. They are old and outdated. Aftermarket replacements are built to slightly different specs and use cheaper components and do not give the same dwell time as the original units and coil output is lower, probably to try to keep the modules from burning up. There are only a couple mfgs of the units - everything you get, either stock replacement or something from one of the aftermarket ignition companies is built by these same mfgs.

I remember when the first HEI units were available for the AMC engines - that was back in the 80's, and I know the person that built the first AMC HEI distributors. Back then, it was a good option. No one had yet figured out that you could simply install the big Ford cap and rotor and use a Ford coil and get better performance and better reliability.

Is the HEI worth the $300 premium over "TFI" (TFI...that is another discussison altogether - TFI has nothing to do with the coil, so referring to it as a "TFI conversion" is incorrect), no it is not. Spend $50 on new parts and install the Ford cap and use a good e-core style coil. If you need to, spend another couple dollars on a recurve kit for your stock dizzy. If you want to improve your stock ignition module, then do what I did and use an external GM module and just trigger it with your stock dizzy. If you really want a high-output system, just use the stock dizzy to trigger a 6A, and you are still into it for less $$ than HEI.
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Old 12-24-2006, 04:04 PM
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The PIG Smith The PIG Smith is offline
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This conversation has been centered on HEI and TFI and the performance issues between the two, but what is the general opinion of a pure MSD solution?
MSD distributor, wires, MSD 6a box, etc...

I know this will cost more, but I would like to discuss this from a performance stand point.
Isn't that what been discussing, ultra fine details of performance of TFI and HEI and not about cost?
So, if cost is not an object, what distributor or ignition system would a person use for an AMC 360 V8?
Bryan Smith
2005 Grand Cherokee Limited - HEMI! Current Daily Driver
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...but if it works, I wouldn't touch it.
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Old 12-24-2006, 04:34 PM
Blown7 Blown7 is offline
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Originally Posted by The PIG Smith
This conversation has been centered on HEI and TFI and the performance issues between the two, but what is the general opinion of a pure MSD solution?
MSD distributor, wires, MSD 6a box, etc...

I know this will cost more, but I would like to discuss this from a performance stand point.
Isn't that what been discussing, ultra fine details of performance of TFI and HEI and not about cost?
So, if cost is not an object, what distributor or ignition system would a person use for an AMC 360 V8?

It has been proven on a dyno that the MSD 6 system will give between 10-15 HP more.

CJ7 401 AMC 6-71 Supercharger,8 psi boost, N2O, 16 fuel injectors, 16 N2O injectors, Bugcatcher, F.A.S.T ECU. Moldex crank, Carillo rods.JE Pistons, TH400 w/ trans lock, QT 1339,<br />Dana 44\'s, Eaton lockers, Toyo MT 35\'s
Old 12-25-2006, 11:03 AM
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Rogue Rogue is offline
360 AMC
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Posts: 3,439 - completely new AMC dizzy for $165 aint bad

now... I can't change what my personal life experience has been and I've been very fortunate with GM HEI

EVERYTHING on a car is a design compromise, whether it be the HVAC engineer trying to fit the unit behind the dash or the bean counter saying it costs too much sooo you really think the factory is gonna use the highest quality components? It doesn't take a very smart person to point out the obvious.

so on to the technical -

if you increase your distributor cap size you also increase the rate of speed the rotor tip travels and this reduces the amount of time you can discharge the spark without crossfiring this is compensated by using larger terminals and/or rotor tips which again is a compromise and every system has them. So... one in one hand one in the other: larger diameter cap with larger terminals and/or rotor tip vs. a smaller cap diameter with smaller terminals in effect produce the same results. my two cents - simply increasing your cap diameter does not net you any more HP or less chance of crossfire - the differences would be marginal at best. so to simply say the GM HEI design is crap because of the diameter of the cap does not fly in my airspace. I'll gladly wave the white flag to the holder of dyno evidence.

The factory HEI E-core is weaker however it was also designed as a total system and when you factor in that there is less total secondary resistance due to the lack of a coil wire then its pretty simple to see that is has only what it needs, again - compromise or bean counters, there are plenty of more powerful coils availble in the aftermarket again pretty obvious stuff - replace the cheap factory replacement parts with parts designed for higher perfomance. in short, ANY system can be optimized it all boils down to how much you wanna spend! and pretty much every argument I've heard about GM HEI boils down to inferior parts not design. high voltage is only needed to start the initial spark. I would be more concerned with how much amperage I could deliver to my plugs and you do that by reducing secondary resistance. The GM HEI is already one step closer to that by design because it eliminates the coil wire. so again one in one hand one in the other - with the same plugs, wires and coil specs the GM HEI will deliver more amperage to the plugs by design.

any inductive system is limited by the space requirements under the hood. they could make a million volt coil but it would take the place of your passenger seat. installing a capacitve discharge system would be a big improvement.

so take the inferior parts out the equation by buying the high performance parts you were gonna buy anyways and what do we have left.... drill a vent hole in the bottom of the dizzy, not too big a deal in my book.
Jeff - 74 Cherokee S 401/400/QT - basically stock
Old 12-25-2006, 03:27 PM
FSJ Guy FSJ Guy is offline
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Why don't some folks like the MSD-6? I have one and it's great. I've used it on 3 different trucks, now. (I keep moving it as I change 4 wheeling vehicles)

Semi OT, but did anyone notice that JYG's posts are gone? Did someone make HIM mad?
Ethan Brady
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Old 12-25-2006, 06:32 PM
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Rogue Rogue is offline
360 AMC
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MSD - 6 is an awesome system, it would be classified as a capacitive discharge syterm. I guess the biggest con I've heard is if it craps out the replacement parts are a whole new unit! at least HEI and Duraspark parts are relatively cheap and availble separately.

as far as JYG I had several earnest sincere technical questions for him that by his credentials he says he has shouldn't be a problem to answer, how that led to him deleting his posts? there are plenty of very sharp minds around here, however most of us have busy lives and I know I try to just come here and help the best I can ( how that is ever construed as wrong is beyond me!!! ) with the time I have and as such I sometimes give the short answer. I may not be an eloquently spoken English degree having type of dude and in my opinion a short answer is better anyways because getting too technical makes it easy to lose sight of your goal. If you spend too much money and time trying to build this perfect ignition system for your perfect engine build stuff like your transmission, engine, brakes and tires get neglected. At least that is the perspective I have after having spent waaaay too many hours and waaay too much money on stuff that in the end didn't really matter that much, but hey to each and all their own I guess.
Jeff - 74 Cherokee S 401/400/QT - basically stock

Last edited by Rogue : 12-25-2006 at 06:34 PM.
Old 12-26-2006, 01:05 PM
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crazydog crazydog is offline
350 Buick
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Originally Posted by FSJ Guy
Semi OT, but did anyone notice that JYG's posts are gone? Did someone make HIM mad?

Oh no! The guy may be technically correct on his information, but his delivery of said information is full of paranoid arrogance that too many people find quite distasteful.
1979 Cherokee - Built 401, NV4500, Dana 300, 6" BJ's Lift w/ Bilstein 5125 Shocks, Goodyear Wrangler MT/R 35X12.5R15, Front Brake Upgrade w/ GM 2500 Calipers & EBC Pads, Rear Disc Brake Conversion, Z&M Jeeps Dash Insert w/ VDO Series 1 Gauges, Tad Rack, Ramsey Hidden Winch w/ REP8000, Hydroboost, CS140

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Old 12-26-2006, 01:26 PM
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AMX factor AMX factor is offline
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I run the MSD Billet dizzy with internal module. Easy to wire in, low maintenance. Adding the MSD external module in a few months when I slide it all over to the race car.
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