When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So about a year ago I decided to try the Dynamod HEI module that came with my DUI distributor. The Delco one that was in there was doing ok. But I read an article that said the some aftermarket "performance" ones were worth a little power at higher RPM. Didn't really notice anything (why am I not surprised... lol). So I just left it in.
Last few drives I started noticing power starting to fall off above ~4000 rpm. I knew the fueling was always right on the money, so I started back tracking what the latest things I did and realized the HEI module. Put the Delco one back in and voila... power came right back.
Even the start up is snappier (guess it was degrading). I use this Arctic Silver thermal compound under the module and it was still nice and fluid, so I know the heat transfer is good.
Must just be the same-ol' same ol' with these unreliable aftermarket stuff. Guess I'm glad it didn't fail outright and leave me stranded.
I don't think Dynomod is cheap- my Accel module wasn't cheap, doesn't mean they aren't a POS. Died on the hwy twice before I went back to GM modules- there is one module that is a little 'hotter' than the rest.
Thats is the one I have. I like using computer icm heat sink grease- very expensive but it works. Also have a little finned alum heat sink attached on the bottom of the hei.
Not sure who makes Napa’s ices or if there the same as years ago. But I bought one for my 92 k1500 with tbi.
still going strong after 20 years and used for a plow so operated 32f and below.
At one time, Dynamod, Accel and MSD were tested to be among the best at delivering high output to the coil. This also established the upper RPM. The GM stocker didn't fare so well.
Now that info is going on ten years old so there's no telling of what the current state of affairs is.
As is usual with these tests, nothing is said of longevity.
Must just be the same-ol' same ol' with these unreliable aftermarket stuff.
QFT.
It's a sad state of affairs, where we've come to in this country, where most such parts are now manufactured in some back-alley Chinese sweatshop with zero care given to even rudimentary quality control. Didn't used to be that way; back in the day, corporate greed wasn't quite so prevalent, and American companies prided themselves on making/building the best stuff in the world.
But times change, as have laws governing the ease with which manufacturing can be moved offshore, and along with quality goes jobs. These days, most repair parts for just about everything, not just for vehicles, are just ****-poor; if the s*** even fits at all, it's gonna let you down early-on.
So an update... looks like my Hypertech coil was on the way out as well. it's probably around 15 years old. I put a spare coil back in (I think it's an old stock one) and picked up about 1/2 - 3/4" inHg of vacuum at idle, and more dramatically my BLM fuel trims increased in value by 6-8 points (indicating I'm getting a more complete burn of the mixture). Seat of the pants, not so much "more power" per se, but definitely a snappier feel to the throttle, feels "peppier".
Not sure what was going out first, the coil or the module.
But I think at this point, I think I'm back to a bone stock ignition, so probably room for more improvement. I'm probably just going to get an Accel coil and module. My reading around online seems to indicate people are pretty happy with the results of that combination.
Haven't had a chance to do the >4000 rpm test (I'll usually have that "fun" early on a Sat or Sun morning when the freeways are empty). But just scooting around town running an errand just now, it was definitely the case that my whole freaking igntion system as on the way out! lol...
I can't remember- I would use Arctic Silver now. Point is GM modules have never given me an issue- trying to hot rod the ignition with Accel failed for me. I use the 369 GM module and also have a drawer full of various spares I have never used. Just disappointed in the experience with a name brand. Also better to learn off of others than to suffer the same expense as well. The GMT400 trucks have a interior/gauge rheostat that has a nice small sized alum heat sink that I modified to sit under the module attached to the hei body.
I always keep an extra module in the car with the tools to change it no matter what module I'm running anyway.
Its like the reviews on Amazon for any given product... for some people it's the greatest thing since sliced bread. For others its the worst piece of junk they ever bought.
I take reviews with a grain of salt- some times its incompetent install or shipping damage, not the items fault at all- other times they are pumped up positive. But when Rbob or someone of his experience says 'this' works I listen, modules are a subject I listened to- cheap at the breakers and at the time I was looking for a MSD module and I think MSD was using GM modules for my application (small cap) THAT said it all. I think most problems in this area barring voltage- would be controlling heat as best as you can and keeping it as cool as possible.
IMO, one issue often overlooked is matching the coil with the ICM for high RPM performance. At high RPM, the ICM has to do 2 things:
1. Provide maximum primary voltage to the coil so the coil can maximize secondary voltage to the plugs
2. Ensure adequate dwell at higher RPMs, which is simply an increased ON time of the primary current to the coil to avoid coil saturation
This is why there are high performance ICMs. Some may be good and some may be bad. That's why there's chocolate and vanilla ice cream. But if buying one, it's clear the manufacturer should be able to provide the above specs that make their product superior to the latest GM ICM (see below). And if not revving to 6500-7000 RPM, the latest GM ICM is likely adequate.
A good article that explains the above. Although written in 2001, still applies today. It addresses large cap HEI distributors, but concepts same for small caps. http://www.superchevy.com/how-to/674...-coils-modules
FWIW, here's some random ICM info collected over the years. Sorry, but attributions lost The ignition module is responsible for turning the ignition coil on and off and controlling the duration of current flow through the primary winding of the ignition coil. This allows the spark plugs to fire at a specific time according to the number of cylinders your vehicle has. It also controls dwell.
ICM stamped '048' (GM 10402827): Retarded the timing advance beginning at 3,500 RPM permitting the use of 83 octane gasoline and the module acted as a speed governor. It seems like the OE Code 048 Ignition Control Module acted like a rev-limiter and limited the ignition advance above 4,000 RPM.
ICM stamped '369' (AC Delco D1943A, GM 19179578): First used on the 1985-1993 Chevrolet Caprice with the 9C1 RPO Police option. This ICM does not retard timing starting at 3500 RPM, but provides 2 degrees additional advance from 4,000 to 5,000 RPM and a total of 6 degrees additional advance above 5000 RPM.
GM replaced the "048" ICM with the "369" ICM. The replacement may not have "369" printed on it. The "048" was discontinued so GM felt like there was no need to differentiate between the two. If the AC Delco D1943A module does not have "369" printed on it, look for the GM part number 19179578 burned on the edge of the module. The 19179578 8-pin ICM was originally for the 9C1 Police Option in a Caprice. In 1989 GM made the AC Delco D1943A ICM (19179578) as the service replacement for all V6/V8 models through 1995. That was because the TBI swirl port (fast burn) cylinder heads needed faster and more total advance. Engines with aftermarket performance camshafts need faster and more total advance.
I'm sure Accel, MSD etc were made much better when these things first came out 25 years ago. Most stuf today is expensive and fails quick. Msd boxes were always hit or miss even back then. Some lasted a few weeks/ months.
A little off topic- but something the OP should consider if the opinions are favorable.....I had a (tested OK) Crane HI6 I was looking forward to installing but ended up binning due to not being reparable (potted electronics). I've had mixed results with MSD and Mallory box's- but when they are working they work well. I had a MSD coil fail- and the MSD box kept the truck running. Just wondering whether to bother looking for a replacement or not, haven't run a CDI box in years.
I had an MSD CDI box years ago that failed. If I hadn't planned for it and wired in the ability to easily bypass with the jumpers I put in my glove box, I would have been stranded. Since then I hadn't had the desire to ever put one in again.
As an update to this thread, I took the car out again this morning to run an errand. It even sounds different... almost silly to say, but it "sounds" like it's running more efficiently (hard to describe).
Any rate, given this is a bone stock ignition now (save for the MSD wires), I'm hoping to get a little boost with the Accel stuff.
lol... Ok, I'm a believer now (even more generally, in hotter ignition systems).
I ran a back to back comparison... this time with some hard data to look at for comparison. My bone stock ignition vs the Accel coil and module.
Yesterday, got it up to temperature and then started taking TunerPro data on the stock module/coil. Then, came home, swapped them for my new Accel coil/module and took out for a drive this morning along with my laptop so I could adjust tuning with my emulator.
What I noticed... (some of it was subjective, but there was some good objective evidence)
1.) Cold start was definitely a little snappier and idled smoother. Even the exhaust note was a little different... a little less raspy.
2.) After getting up to temperature, it was clear the throttle response was also snappier. What I also noticed was there seemed to be less bouncing around of the AFR on the wide band. I was also able to actually lean out the off-idle throttle tip-in a little.
3.) As with the cold start idle, the exhaust note was a little different. Hard to describe... smoother, more melodious...
4.) The most telling thing was that I actually had to richen up moderate throttle to WOT fueling by about ~5% in order to get my AFR back to where it was (pretty much from 1500 rpm all the way up to 4500), and in doing that the power increase was very noticeable. Definitely not like 30 hp or anything like that, but it was noticeable. I played around with spark timing a little, but if there was any changes, it was to insignificant feel by seat-of-the-pants.
I guess I don't know what the biggest difference was, the coil or the module, or if it needed both to realize this improvement. I've never done a A-to-B run like this before. When I did my Hypertech coil so many years ago, I had the stock module. But I don't recall this kind of dramatic difference with the coil upgrade (I probably would have remembered). Then when I recently put in the Dynamod module, I didn't notice anything. And of course, either the module or the coil started to fail, at which point I went back to stock and regained power that I lost from the failing components. So yeah, never a super crisp configuration difference with which to compare.
Of course, this experiment assumes that the stock module and coil are in good working condition, but I think they were given the "improvement" I got over the failing components.
I think I'm going try an ignition box too (though maybe around Christmas time frame). For now, I'm very satisfied with this setup. I guess all that remains to be seen is the reliability of parts over time. I put the Arctic Silver thermal compound under the module, so it should have a very good conductive heat path.
I recall Grumpy at one point posting that he thought the CnP on the LS motors was worth 50hp. I remember he installed that in the GN and later flipped to multiple CD units.
lol... Ok, I'm a believer now (even more generally, in hotter ignition systems)..
I think you just proved: IMO, one issue often overlooked is matching the coil with the ICM for high RPM performance. At high RPM, the ICM has to do 2 things: 1. Provide maximum primary voltage to the coil so the coil can maximize secondary voltage to the plugs 2. Ensure adequate dwell at higher RPMs, which is simply an increased ON time of the primary current to the coil to avoid coil saturation
While not initially stated, #1 also applies to any RPM.
LMAO... I can't believe this ignition setup. I took the car into work today and surprised myself when I had to hit the gas to pass someone at about 3500 rpm. My head got thrown back a little as I wasn't expecting the kick this thing has. It was never like that before even when the old ignition was at its best. Usually you subconciously brace yourself to avoid that, but I braced myself according to what I remembered and it wasn't enough
It sounds ridiculous, but after the minor retuning to take advantage of the better igntion, I wouldn't be surprised if I picked up 10-15 hp over the previous ignition even when it was in good working order.
That and I picked up about another 1 mpg cruising along in 8th gear.. was 29-30... now 30-31.
That said, I'm not sure I'm going to do the ignition box at this point. Might be diminishing returns by now.
I may end up putting the money into some 1.6 rockers. Get a couple of more effective degrees of camshaft. Figure ~10-15 on those.
$170 for the ignition stuff and ~$200 for some decent rockers... ~$370... not bad for 20-30 hp.
LMAO... my whole ignition system is crumbling right before my very eyes!
out for a drive today and started losing power again... I'm like the WTF now?
Then it got to the point of a hard (but intermittent) misfire at idle, so I figured ok, probably a plug wire or something (my wires are probably 15 years old by now).
Got home and started to pull off a few wires... the #4, #6, and #5 spark boots literally started crumbling in my hands and the #6 and #8 wires were nearly severed completely right where they entered the boot from heat damage.
Hilarious.... coil, module, and wires all failing at nearly the same time! They were the MSD 8.5mm superconductor wires and they ran exceptionally well up to the point, so I just ordered another set. I also ordered some protective heat shields this time since the boots live pretty close to the headers.
Amazing that I saw such a huge improvement from the coil and module with wires nearly failing. Wonder what I might see with new wires?
Took the wires off this morning and did some resistance measurements....
Keep in mind these are supposed to be 50 ohm/ft...
1.) Intermittent open, bouncing between that and 1.1 k-ohms
2.) 160 ohm
3.) 525 ohm
4.) 2.9 k-ohm
5.) 143 ohm
6.) Completely open (probably finally broke completely during removal)
7.) 78 ohm
8.) Intermittent open (couldn't even get a stable reading when it would connect).
Lol... these really must have been on their last legs. I guess they did last ~15 years, so I definitely got my use out of them. Not bad for aftermarket, which is often not known for high-quality
I've had taylor wires on ole ttop for at least 20 years. They are still kicking and soft even the boots. My headers are Jethot coated and that reeeeeeally helps with the heat.
Ditto MSD 8.5s comment. Not reliable. All of a sudden, had intermittent miss. One wire was open but only if slightly moved it at the plug boot. Were < 2 yrs old on a car that gets driven less than 100 miles a month. MSD agreed to make me 2 new wires at no charge (1 to install and an extra). Very nice gesture. Received the NEW wires. One was 150 ohms per spec. The other 2500 ohms. Go figure. Seems when a company gets acquired by Holly, they have a tendency to go south.
I bought a set of MSD 8.5s 13years ago w my first ZR. Prior to that I was using 8.5s on my 84 Xfire. Still work and ohm well. I had replaced them w Magnecores for a few years. I must have one of the batches produced here in the States and not China.
Annnnnnnd....the saga continues. The Accel module failed already. Almost had a feeling it was too good to be true...
Was driving yesterday and I started noticing the speedometer needle bouncing around. Then today I'm on the freeway and the engine starts intermittently cutting out. Stalled once at a light on the way back home. I figured it had to the HEI module.
When I got home I swapped the factory GM one back in, reset the spark latency table from above to factory and drove it around for an hour with no symptoms.
Ugh... what a piece of junk. Looks I'll be sending it back.
Car feels a little down on power with the factory GM module back in unfortunately, but not as much as I would have expected. I guess the concept of the module influencing power output must have some amount of merit to it. But I think the new spark plug wires had a lot to do with the overall improvement I was describing before. Any rate, I'd definitely sacrifice a little bit of power for knowing I'll get back home without a tow truck when I go out for a drive.
They must run these "performance" modules too hard for their own good... my guess is the thermal conductivity of that connection to the HEI base is insufficient to keep this thing cool... or maybe the HEI base is actually too hot to make a good heat sink.
One thing though, I re-ran the experiment about checking the spark latency table with the factory HEI module.
It was 5 deg too advanced with the latency table developed around the Accel module. I put the factory ANHT/AXCN large cap HEI table back in and viola, right on the money.
I've got some 1.6 roller rockers on the way for Christmas, so hopefully gain back what I lost.
Yup, was hoping you got a good ign module but I've never had any luck with the "performance" stuff in that area.. May work for a few hail mary dyno or 1/4 mile runs but if you want it to last...
ULTM8Z -- Sorry for your issues. I got tired of doing the distributor component replacement thing into a 35+ year old distributor, so ordered and installed this complete distributor with cap and rotor. It has the High RPM ICM. Works as it should!.Have not done the latency test on it, but no irregularities noted at high RPMs https://www.jegs.com/i/JEGS/555/40006/10002/-1
A few days after going back to the stock GM HEI module, I decided to resurrect my Pertronix external coil and the MSD external coil conversion kit. Didn't notice significant improvement one way or the other over the Accel coil. The Pertronix one is their 60 kV coil. I ended up taking a chance and getting the Pertronix HEI module.
Noticeable improvement in idle quality and torque. Pretty much feels like when the Accel module was working properly. I actually went back and put my old Dynamod module back in (the one that was failing and kicked off this whole saga originally). Definitely felt a very significant drop in power and driveability, over and above even the GM one.
There's no doubt in my mind now that these performance modules aren't necessarily gimmicks. It's just the reliability that's always suspect. Now if only this Pertronix module one lasts... But so far it's doing well... I've been driving it around quite a bit and probably have more miles on it than I did with the Accel before it failed.
I talked to Pertronix a little before I ordered it from Summit (and granted, I know they're eager to sell me stuff), but they were saying the things that often kills their modules are (of course) lack of, or inadequate thermal interface material, bad spark plug wires or non-suppression type solid core wires. I'm using the Arctic Silver thermal compound and the MSD wires are suppression type wires.... so we'll see what happens.
Needless to say, I have my GM module and the distributor cap with the internal coil in the trunk, just in case. But hopefully it lasts because I'm really enjoying the performance improvement.
I fabbed up a bracket to mount it on the valve cover. Used non-metallic spacers and rubber grommets to mount the coil to the bracket, to thermally isolate it. Does a pretty good job of it since after I get home and shut off the engine, the coil is actually quite a bit cooler than the valve cover. Without the engine heat flowing into it, the cooling fins on the coil seem to do a good job of keeping it cool. I basically just didn't want to drill holes in the firewall.
But it looks pretty cool IMO sitting up there. Kinda has that coil-on-plug vibe to it...
It seems like all of us have had problems with the HEI modules.
I have two setups that seem to work well.
1.
GM HEI Module.
GM Coil.
GM or Accel Cap and Rotor.
Taylor Wires.
This setup is good for a mild performance build.
2.
MSD Digital 6A.
MSD or GM HEI Module.
GM or Accel Coil.
GM or Accel Cap and Rotor.
Taylor Wires.
This setup is worthwhile for the more radical builds.
I am a fan of hotter ignition setups and copper based plugs for a Gen 1 SBC. As long as the ignition is not too hot and prematurely wears out the plugs.
The coil turns ratio, wire diameter, and primary “current vs. time” characteristics can be modulated to customize the spark events.
Sometimes the coil primary impedance is a bit low and this results in higher output current draw from the HEI module. The end result ( until the saturation current of the output transistor is reached ) is more heat and possibly reduced component lifetime. Of course, all depending on the heat sink compound thermal conductivity.
I reached a certain age years ago where I decided I would peel off some layers of 'reliability' like an onion- basically give up some zip and go back to oem in certain areas- which includes the distributer assembly, other than blueprinting the unit and adding a finned heat sink directly under the module, I just picked picked the choice GM components, I used to like Accel caps but they are chinese now.
You know what......zero issues since then.
Have had zero issues with Davis Unified Modules in my TBI and Vortec engines over the years. Also had good luck with both Taylor and Accell 300+ race wires. Same cannot be said of any cap and rotor. None lasted more than a year or two on my Vortec although my TBI caps lasted a while longer.
Have had zero issues with Davis Unified Modules in my TBI and Vortec engines over the years. Also had good luck with both Taylor and Accell 300+ race wires. Same cannot be said of any cap and rotor. None lasted more than a year or two on my Vortec although my TBI caps lasted a while longer.
Is that a common complaint about vortec- between the composite body or the cap?
09-20-2020, 04:13 PM
