If you are trying to make it pretty, go for the DUI.
But the DUI is only a "prettied up" HEI with aftermarket springs and weights you end up replacing anyway.

Sounds like your module is dying - Ford modules have that reputation. Replace it or upgrade to an HEI.

 

If you take your module off and take it to a parts store like NAPA or any brand name store most will check them free of charge. It also could be the pickup coil in the distributer. (I think maybe I spelled that wrong)If there is only 2 wires going to it take an ohm meter between the 2 terminals and see if there is continuity, pull and wiggle the wires to make sure one is not broke. The vacume (sp again) advance moves these wires constantly so they have a tendancy to break. If it's bad it's easy to change all you have to do is put a nickel on top of the shaft and use a battery cable puller and pull the fingers off then replace the coil and tap the fingers back on. But be carefull not to press /ubbthreads/images/graemlins/40BEER.gif it on to far. You don't want it to rest on the coil (they used to come with a guage to keep it from hitting). Also you could have an EGR valve sticking. To check it plug the vacume (sp again) line going to it and see if it runs OK then. If it does replce the EGR. Hope this helps Good Luck.

 

The problem with checking the module on a tester is it most likely will test good. Since it's intermittant, and probably only does it when warm, chances are it'll test good.

One way to test it - put a drop light right on the module to warm it up while the engine's running. If it quits running, replace module. That can prove it's bad, but cannot prove it's good.
The Ford modules are cheap. Unfortunatly they are so unreliable a new one could be worse than the one it replaces.

There are 3 wires from the pick-up coil. Orange and Purple are the PU coil wires. Black is ground - the only ground for the entire ignition system. That wire goes into the rubber grommet on the distributor, then to a ground tang just inside the distributor. Make sure the screw on the tang is clean and tight.

And, as suggested, ohm out the PU wires while wiggling them.

 

Re: 401 is dying at stops and low speeds occasiona

Nate....I would highly recommend a DUI distributor.I just installed one on my 304 in my Commando,and what a difference.And a set of live wires.Yes,they are pricey,but are more than just a "pretty" distributor.They are a good quality investment.You can go the pieced togather junk yard rebuild or another brand and save a few bucks,but you get what you pay for. You can ask Al about the "save a few bucks HEI".Of course he has a Chevy in his Jeepster,so the HEI's are a little less $$$. I can just imagine what a DUI would do for that big,bad 401! Good luck! /ubbthreads/images/graemlins/usflag.gif

 

Re: 401 is dying at stops and low speeds occasiona

He He -- Interesting how bead blasting an HEI housing and installing stock GM parts with a "performance" sticker can make it run so much better.

Just thought I'd explain why I called it "pretty."

They start with a GM HEI - for the AMC I think it only needs a different gear to make it fit.

Yes, as the DUI advertising says, it has a longer dwell -- longer than a stock Ford system, but the same as a stock GM because that's all it is. It's physically not possible to have a dwell time longer than a stock GM. If it was longer, it would shorten burn time. 8-10 degrees at idle, about 30 at 2000 with a current limiter.

The pick-up coil is the same stock GM too.

The coil - may have a higher turns ratio - increases AVAILABLE voltage, but reduces current. Makes for a thinner spark. They advertise 50 KV available output, yet the plug only needs 10-18 KV to fire.

Then the "smooth" curve they advertise -- if the old HEI is defective the curve isn't smooth, so it needs repair. The way they "curve" the DUI distributors is by installing MR. Gasket weights and springs -- the difference between their "racing" and "performance" curves is which weights and springs they use. The "racing" type uses a combination that brings in the advance real soon, all the way in at about 1800. They assume you launch at 3000.
The "street version" brings the mechanical in about 2300.

Re-installing the stock GM HEI weights and springs will give better low and mid-range performance. If you have a distributor machine you could even regrind the weights to come in even slower, better yet for torque.

DUI even uses the stock non-adjustable vacuum advance.
They say to set initial timing at about 12.
When the distributor is fully advanced the total timing gets to about 43-45 degrees. Way too much!
You don't want total timing much more than 35 degrees. More than that shortens engine life - the piston has to compress far more pressure than it was designed to do - breaks rings and causes inaudible detonation, and may even cause the engine to run hot.

So you end up installing a Crane Adjustable Vacuum advance and stock GM HEI springs anyway. Since the stock GM diaphram was designed for a different carb than the AMC carb, the curve will be wrong anyway. That's why using the adjustable, and setting it correctly, is needed anyway. About $25. (Be sure to set it at the "least sensitive" position and set the tiny limiter cam it comes with - to about 1/3 travel - 12 degrees to start.)

For off road use you want low end torque - requires a slow timing.

In the last month or so I've re-curved 4 DUI's - I've been getting them fairly frequently lately. Each time it's made a big difference in how they ran, especially at low to mid range. One Bullnose, one CJ-5?, and 2 Chevy pick-ups.

Another neat, and cheap way - use the stock distributor already in the AMC.
1. Convert to the bigger Ford cap. The adapter and cap clips right on.
2. Use the pick-up coil to drive a remote mounted HEI module. (Module must be mounted on a good heat sink.)
3. Use the HEI module to drive a Ford TFI coil, or a remotely mounted GM HEI coil.
4. Eliminate the ignition resistor.
5. Install silicone 8mm HEI wires.
6. Regap stock plugs about .010 wider.
Simple and extremely effective.
That way the original advance system is retained but the power of the ignition is greatly improved! And it's less than $100.

Give it a try!

 

Re: 401 is dying at stops and low speeds occasiona

If the distributor is from a '77, that should be the Prestolite distributor (if my memory serves me correctly, that system was used from '75-'77, transitioning from Delco w/points to the Motocraft in '78).
The easiest way to identify it is that the vacuum advance is made of plastic.
While I was an AMC/Jeep tech /ubbthreads/images/graemlins/codger.gif, there was a recall (actually, several), but this one was called the "Igwire" campaign (AMC had some real winners!!). What that involved was to cut out the plug-in connector on the distributor lead and solder the wires together, then put heat-shrink tubing on the wires for insulation. Your problem sounds suspiciously similar to the symptoms the recall was supposed to correct. Of course, it didn't, and those ignition systems were a real headache for both the owners and the technicians. You could end up replacing ALL of the ignition components, and still have problems. /ubbthreads/images/graemlins/wall.gif
The Prestolite was famous for the vacuum advance diaphragm failing. Then, like a lot of vehicles in that time period, if the engine idle was too high, it would run backwards when the switch was turned off, forcing intake gasses into the distributor through the vacuum line. Then, as soon as you cranked the engine and a spark hit the gases, BOOM!!!, the distributor cap was blown off. /ubbthreads/images/graemlins/AR15firing.gif
If you want a cheap, dependable upgrade, just stick in a '78 (or later) Motocraft system. Parts for those are cheap now, and there was a post on the board describing how to make it deliver better performance, using over-the-counter parts, for a reasonable price. /ubbthreads/images/graemlins/thumbsup.gif

 

Re: 401 is dying at stops and low speeds occasiona

OOOPSSSSS...
RRich posted the Motocraft system upgrade right above mine.
I guess I should read a little more closely!!! /ubbthreads/images/graemlins/bag.gif

 

Re: 401 is dying at stops and low speeds occasiona

Yup -- explosive!!! I nearly lost an eye when one blew up on me. Part of the cap hit me in the face knocking me silly.

The Prestolite was a very poor excuse for an ignition - or starting and charging systems. But they were cheap!

The Motorcraft really wasn't great either, but far better than the Prestojunk.

The Motorcraft (Duraspark) ignition has an output the same as a points type ignition, just no points to wear.
Upgrading to a HEI module greatly increases the output - a noticable difference.

The HEI module can operate with the Ford TFI coil (the square one,) or the round DuraSpark II coil, or preferably the GM HEI remote coil - more "snap", and the ignition resister is eliminated, so there's lots more power in the system.

Using the larger cap is not absolutely required, but it's a good mod. The larger cap has the terminals farther apart so it's a better High Voltage insulation, plus you can use the better insulated 8MM wires.
(The later Ford DuraSpark II and the TFI were much better, far more reliable and had the same ouput as the GM.)

For those wanting to retain the "stock look" you can hide the GM module somewhere and use the original cap.

GM first came out with the standard HEI in '75, by '77 I was already retrofitting the modules into Ford and Chrysler systems - even into a couple of Porches, some Fiats, Jags, Mercedes, all kinds of stuff. I even developed a points driven HEI conversion for purists -- but I was never happy with it.

He He -- Later on some of the Fiats, Subarus, and Jags had a big ugly looking heatsink they called the "module" - Fiat & Subaru was around $700, Jag was about $1200. Pry off the back cover and you found a stock $35 GM module!!!!

I recently suggested using the remote HEI on the Offroad.com Short Wheelbase board. Since then several guys have done it - a couple of great write-ups have resulted from it - pics and all. All of them have reported great improvements in starting and driveability. Do a search.

Specs:
Points type, Prestojunk, Motorcrap:
28-32 KV available voltage.
.75 MS spark burn time.

GM HEI:
35-40 KV
2.5 MS burn time
About 3 times faster rise time.

A faster rise time helps fire the plugs - can even blast crud off an electrode. The same principle that makes CD's work so well - like the MSD. Kinda like using an impact wrench on a stuck bolt.

The longer burn time helps get more particles of fuel burning at the right time -- like using a bigger match to light the BBQ. Problem with MSD is the burn time is extremely short - the nature of a CD. The MSD's "multiple firings" are only at low R's too, below about 2000 RPM. There's not enough time between the short firings to discharge then recharge the capacitor at the higher speeds. Even then, MSD's a definate improvement over any stock ignition except HEI.

Some aftermarket coils claim 50, 60, even 80 KV output. Of all the aftermarket coils I've seen, and that's a bunch, none have ever exceeded 40 KV - same as stock. Of course I didn't test the output like they must have by using 36 volts to drive it! Many take the stock GM coil and pot plastic around it to change the appearance. Crack it open and find a stock coil!
Since it runs on 12 volts, if you were to increase the turns ratio to increase the output voltage, the output current would proportionatly reduce. It would have the same energy.

The "performance modules" are the same way -- who would believe a company like Accel, DUI, or Bubba and Yahoo would spend the millions of dollars to develop a new chip and mount it on the same plate just to sell a few at Autozone?

The next step up from the HEI in performance is a Direct Ignition System. Since each individual cylinder, or pair of cylinders use a separate coil, charging time for the coil is longer - more energy can be packed into it - for a much better spark. There are a few being made now for racing -- but very very high $$$$. The increase in performance on those is at the very high R's, like 10,000+ RPM.

Something very important -- use the stock original plugs -- do not use the plugs from an engine that uses the HEI. The plugs are designed to match the combustion chamber, not the source of ignition. Avoid the aftermarket trash - "Made to sell, not to use." Things like reach, heat ranges (throughout the entire operating range) and indexing are all considered when the designers selected the plugs to use.
Simply open the gap a bit more to expose the mixture to more spark area -- because you can now!

Sorry for the long post and shotgunning info.

 

Re: 401 is dying at stops and low speeds occasiona

I really like the idea of the HEI but I don't really follow what parts to use for the module and matched coil. I've already upgraded the Motorcraft distributor with the spacer,wider cap and a good set of 8mm wires. Also I grounded the distributor black wire to the engine block too just to make sure it was grounded ok. I would love to get a little more life out of these components before I go DUI. Sounds like I'm pretty close to a full HEI conversion. It is not the prestojunk as you guys described. The vacuum module on the distributor is a metal housing. How would the nipple on the end of the vacuum module affect anything if it were tweaked a little when I transplanted the motor? Like I said the motor cuts out immediately when it does die randomly. Great ifo keep it coming guys. I have Monday and Tuesday off this week to try a few things. Thanks a TON!! Nate

 

Re: 401 is dying at stops and low speeds occasiona

I would really like the P/N's or years of vehicles that these HEI components come on. I'd rather do it all at one time and hopefully cure this issue.Can someone send me a diagram of how to interconnect all the HEI components. That would really help a ton. Nate

 

Re: 401 is dying at stops and low speeds occasiona

My 86 waggy did that with a bad egr valve.When you hit the brakes you push a shot of air into the intake with the master cylinder brake booster bladder.Mine would stall at every stop.Take off egr and make a gasket to block it off.Look for vacuum leak.Thats what mine was.Block off vacuum line for booster.If engine stumbles when you hit the brakes ,is that the problem?If it does your too lean at idle or have a vacuum leak.Been there done this got the hat.

 

Re: 401 is dying at stops and low speeds occasiona

I forget who, but someone did a great write-up on the short wheelbase board about 1.5 months ago, about the the Ford/HEI conversion. Pictures, part numbers, wiring diagram and all.
Anybody remember who?
The hardest part is fabbing a good heatsink, and that's easy.
Someone also put the HEI module in an old Ford module box - neat - seems like they called it Stealth HEI?
Since you've already installed the larger cap and wires, you are 1/2 way there!

Yes, a bad booster could make the symptom. Try it fully stopped - push on the brake pedal - if the engine speed changes appreciably, the booster's bad.
If the EGR's stuck open, it'll run bad all the time.
If the spring's too weak, or the wrong vacuum, it could cause the symptom. Disconnect the vacuum line to it to see if that helps.

 

Re: 401 is dying at stops and low speeds occasiona

It is actually a "new" billet aluminum housing with performance parts and a watch your fingers cuz your hair may stand on end pretty sticker.And a big difference it truely makes.My gas milage has gone up 3 mpg,starts much easier and a hell of a lot more poop! AMC V8's are cold blooded suckers.Not any more.Hot Rod mag had a write up a few years ago,as did Car Craft or one of those mags,and it was all good.I know three other people with DUIs,and all are very happy with them.And if you ever need to replace parts,stock GM works.That is the great thing verses a Mallory or some other aftermarket electronics.You can't stop at your local Kragen and buy parts,not that they would know what an HEI was anyway. /ubbthreads/images/graemlins/thumbsup.gif

 

Re: 401 is dying at stops and low speeds occasiona

I have to add a quick vote for the EGR system being the culprit. The first time an EGR went bad on me, in my 93 GMC K15oo, the symptoms were exactly what you describe. I did everything from HEI pieces, cap, rotor, plugs, wires, etc. I finally gave up and took it in for what I had about decided had to be a bad puter chip or failed EFI piece. Nope, faulty EGR.

So when the EGR in my wife's van went bad here a fews weeks ago, causing the same rough idle and die-off, I knew exactly what it was and how to fix it. One EGR valve and one solenoid, 45 minutes total, done.

Ain't it amazing how sharp we can convince ourselves we are when we do something right the second time, after being totally lost the first time?

The big headache to this is that it is intermittent...it's hard to diagnose because it keeps messing with your head by cutting in and out.

Good Luck

Robert

69 Rattle Can Camo Commando

 

Re: 401 is dying at stops and low speeds occasiona

If I remember correctly I believe someone recommended just pluging the vacuum port on the EGR and leaving it there as just a plug.This is the way I have it setup currently.Will leaving it plugged cause a stumble every now and again.I don't believe it would but you never know.

 

Re: 401 is dying at stops and low speeds occasiona

Is there a difference between an MSD 6 box and an OFF-ROAD version. I have a buddy with a used MSD 6 box for cheap. What about under hood vibes and such seems to me that it will be fine. What do you guys think.Someone has to have one on an occasional off road ride. Nate

 

Re: 401 is dying at stops and low speeds occasiona

There are two easy ways to check the EGR. With the engine running, either connect a live vacuum source to it, or reach underneath the top of it and, using your fingers, pull up on the diaphragm. Either one of these methods will open the EGR. Alternately, if you have access to a hand-held vacuum pump (Autozone, maybe...), you can use that to apply vacuum to the EGR.
If the idle changes, then you know the EGR is sealing. If not, then it's stuck open.
If it's stuck open, there are two easy ways to fix it. Either remove the valve and free it up so that it easily moves all the way to the closed position, or just cap-off the opening on the manifold (probably the best solution, as that's a permanent fix).
As far as plugging the vacuum port on the EGR, there's no need to do that, as the EGR valve is not a vacuum source.
If this doesn't help, my first recommendation would be to put a vacuum gauge on the engine and see if it's got good vacuum at idle(18-20 in.). If not, then you probably have a vacuum leak somewhere. The most likely sources are vacuum hoses, brake booster, or, since you probably have a 4-bbl carb, the insulator/spacer at the bottom of the carb. The worst-case scenario would be a leak around the intake gasket where it seals to the heads.
One other thing that I remember being a big problem on the 360's and 401's when I worked for AMC/Jeep, in the event that you have the original Motocraft carb, is that the secondary butterflies sometimes will stick open very slightly, causing the same symptoms. Take a pair of pliers and gently twist the linkage on the secondaries toward the closed position.
If none of these fixes help, my next step would be to replace the ignition module, as I've seen Motocraft modules with these exact symptoms many, many times. The problem is that the module is beginning to fail, but it's not completely gone.
I hope some of my babble helps you get this solved.

 

Re: 401 is dying at stops and low speeds occasiona

Ok so I have tested and tried all the things you guys recommended and have came up with a few other questions. I'm going to replace the module first to try. I put a halogen light on it and let it get up to temp at an idle.The motor wouldn't die all the way as it sometimes does but I did notice an erratic idle after a while.I'm also wondering if it is too much fuel at lower speeds and stops.Does having a fuel pressure regulator make that much difference at idle if say it is a consistent 7psi as Holley rates their pump.I tried swapping the fuel filter to a three outlet style to alleviate any excess fuel buildup and the engine ran real poor.I've also tried shutting the fuel pump off at the switch when it starts stumbling and it doesn't seem to help to much. Any other info would be great. Nate

 

Re: 401 is dying at stops and low speeds occasiona

Oh yeah, since I'm not running the points style ignition,do I still need to run power through the ballast resistor on the firewall? Thanks Nate

 

Re: 401 is dying at stops and low speeds occasiona

After some more research and few quick changes to the way I wired in the Duraspark ignition all seems to be running the way it should. I now have a smoother idle and it seems to accelerate maybe a little better due to a more consistent spark. For you guys wondering ,the ignition box needs constant 12v and the way I had wired it it was only getting 11v. Seems to be OK for now. Thanks for all the help. Nate