Author Topic: Got Hemi back from shop  (Read 2989 times)

Offline Mike71Cuda

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Got Hemi back from shop
« on: September 08, 2008 - 04:01:07 PM »
I had my 71 in the shop with the new Hemi for some heavy valve chatter. The guy adjusted everything and did some other stuff but he told me the car could use a little hotter spark than what I have (orange box with elec setup-out of the box). Not sure I want to go into  the MSD 6 /7 thing. What are alternatives, if any
Car is ok at idle and when you are at higher RPMs but going from 25mph and hitting the throttle there is a lot of bog and some misfiring. I am going back to him for tweaking this but want to have my facts straight.
any help out there?




Offline Changin Gears

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Re: Got Hemi back from shop
« Reply #1 on: September 08, 2008 - 05:11:21 PM »
High RPM is when an ignition system is under the most stress,  if it is working there I would look elsewhere (fuel).


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Offline moper

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Re: Got Hemi back from shop
« Reply #2 on: September 08, 2008 - 06:33:44 PM »
I would have him test the hot side of the coil. If you have a voltage out of the ballast of less than 8 volts, the coil may not have enough juice. Std Ignition makes some that are like .8 ohm as opposed to 1.2ohms. You should have plenty of spark.

Offline hemiken

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Re: Got Hemi back from shop
« Reply #3 on: September 08, 2008 - 06:55:49 PM »
You could always put in a Mopar Chrome box and a MSD Blaster Coil for a standard look. :2thumbs:
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Offline 71chally416

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Re: Got Hemi back from shop
« Reply #4 on: September 08, 2008 - 07:08:31 PM »
Those old Chrysler ignitions are what they are. They're just as old and outdated as the old factory cams are wheather they're chrome or orange box. Even the ignitions on the new trucks have much more spark than they do. There are better ignitions now that don't cost all that much and their is no stigma attached to having a superior ignition.
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Offline MEK-Dangerfield

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Re: Got Hemi back from shop
« Reply #5 on: September 08, 2008 - 07:21:48 PM »
How do your spark plugs look? The bog could be a carb problem...or a timing issue.   :dunno:


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Offline Supercuda

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Re: Got Hemi back from shop
« Reply #6 on: September 08, 2008 - 07:50:38 PM »
This is a tuning issue, not a parts issue. If you need a hotter spark in transitional rpm, then it is not the ignition system's fault. Changin Gears is correct that the problem is somewhere else if the ignition is ok under greater or lesser stress. If it is missing and falling on its face at these lower rpm, then it is time to double-check all factors of the tune: idle mixture and speed; initial timing and advance curve; fuel quality; air quality (is your air cleaner dirty?); and some factors that aren't usually considered: transmission and/or clutch condition; traction issues (if a limited slip is failing, it may just feel like a miss); and also the obvious possibilities of an improper valve adjustment, or the omission of checking all tune-up settings after setting proper valve clearance. Looking at the spark plugs will help you determine which way you need to go first. If they are fine, and show no signs of a lean or rich condition, then it just may be another problem, and not the tune-up. I hate it when people blame the technology because they don't know how to do a tune-up. It only gets worse as the automotive service industry gets younger, as we older guys aren't out there doing the hard stuff any more, and auto "technicians" don't know how to adjust parts, just how to replace them. A good mechanic will check everything associated with an engine's tune, when he has to do something to any part of an allied or affected system. The old, Chrysler electronic ignition hasn't changed much in the last 30 years because it doesn't have to; it's fine as it is. Computers and digital control boxes are pretty special, but they aren't any better at lighting a spark in a stock or near-stock engine, than the points system that the electronic ignition replaced in 1973. Running more voltage than the designed 6V nominal voltage, just stresses components. If your spark needs to be hotter, the Blaster coil is a fine idea; the coil used by Chrysler on the 2.2 and other, later engines is also a good choice. You are looking for the little epoxy-filled units that look like DIS coils without the fancy connectors. It has a dedicated, weatherpack plug, but is easy to use and durable, to boot. It fires my 383 under all conditions, and could probably even work with a .050" gap in the spark plug, but I run mine at .045". With the electronic ignition and the orange control box, the spark is hot enough to work fine with a .045" gap, and I do it to all engines equipped with the orange box.

Offline 71chally416

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Re: Got Hemi back from shop
« Reply #7 on: September 08, 2008 - 11:33:30 PM »
An excert from an old High Performance Mopar magazine article on a mild 360 buildup, for what it's worth.

"The next upgrade we performed was removing the stock electronic distributor and installing a Davis Unified Ignition (DUI) from Performance Distributors. The DUI is an HEI-style ignition that can really leave a lasting impression on you. In the past 15 years, we've changed from points to electronic ignition, added external spark amplifier boxes, and sensed a small difference. The intense DUI made a tremendous improvement in the smoothness, performance, and driveabiity of our breathed-on 360. Without the carburetor's choke hooked up it would take over 5 minutes of foot on the gas pedal until our motor would idle smoothly. This was with the stock distributor reworked for full advance all in by 1,500 rpm. With the DUI installed we could have eliminated the MP orange box, but we left it there for Looks. Once the DUI was installed, our powerplant would easily idle after only 30 seconds of warm-up time. The DUI directs additional spark energy to the plugs, allowing the plug gap to be opened up to.055. The DUI worked with our combination as a team helping our engine produce outstanding driveability, efficiency, and low ET's. The DUI is the best ignition upgrade "yours truly" has ever done."

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Offline 73Chally

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Re: Got Hemi back from shop
« Reply #8 on: September 09, 2008 - 08:45:16 AM »
That looks like it was a definite improvement, but doesn't 5 minutes to warm up indicate some other type of tuning problem that a new ignition system might be masking?  What did the factory stock race teams do back in the 60s/70s with their ignition systems?  Does anyone know?

Offline 71chally416

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Re: Got Hemi back from shop
« Reply #9 on: September 09, 2008 - 10:56:57 AM »
I'm not saying the ignition is the cause of this particular problem, or the tuner of the car knows what they're talking about, but just that there really are much better ignitions today then there used to be. If this one (not an endorsement because I don't use a DUI) even helps a mild small block idle better, it will definately help a big block.

Some used the factory "Gold box" Ignition back then. It wasn't recommended for continuous use on the street though, and I'm not sure they even still make it. Even back then the MSD ignitions were used by racers. The newer ones are much better and have built in rev limiters. You can probably get a Digital-6 for the cost of the Chrysler conversion kit + an add-on rev limiter. Remember this car? Look at sticker on the fender.


 
« Last Edit: September 09, 2008 - 11:12:51 AM by 71chally416 »
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Offline moper

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Re: Got Hemi back from shop
« Reply #10 on: September 09, 2008 - 11:50:38 AM »
This is a tuning issue, not a parts issue. I hate it when people blame the technology because they don't know how to do a tune-up. It only gets worse as the automotive service industry gets younger, as we older guys aren't out there doing the hard stuff any more, and auto "technicians" don't know how to adjust parts, just how to replace them.

I agree with this 100%. However, I do disagree with the "6V designed spec" remark. That's for factory cylinder pressures and mixtures and fuel types that don't exist in pumps anymore. In most HP builds, that designed spec has been altered to hurt idle and low speed characteristics. 8V is not enough to "burn up" a coil. Many cars that run the aftermarket replacement ballasts are now running under 6V to the coil hot, and even more have issues due to voltage drop from the battery to the ignition side of the ballast. If there's only 11.2 going in, then they'll be close to 5 coming out. that's why I suggest starting the checks there. Hemis do not idle cleanly. They can be made to idle smooth, and well, but never clean. It's a function of the port and valve at low rpms. Not the chamber or lack of tuning savvy. Changing to a better ignition is a simple way to get more power, but I would prefer to get it from making a good part better, rather than simply throwing money at it and then saying"yeah" when it is better, but still needs tuning to be right.

Offline 73Chally

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Re: Got Hemi back from shop
« Reply #11 on: September 09, 2008 - 12:48:15 PM »
Aren't Hemi's kind of dogs at low RPM to begin with?  I know their bread and butter is the high RPM range, and I though that was why the 440 was always considered a much better street motor.  With that said, it still should not be stumbling as much as you say it does, but overall could it just be a matter of where do you want it to perform best?

Offline 71chally416

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Re: Got Hemi back from shop
« Reply #12 on: September 09, 2008 - 12:51:46 PM »
Tom Hoover (I assume any hardcore Mopar guy knows who he is...) was questioned about the new Hemi and what he thought they should change on it relative to the old 426 while they were designing it. One of his suggestions that was immediately adopted was dual plugs for cleaner burning. In the absense of dual plugs and a coil on each plug, the hottest spark possible would seem to be a good thing with the gas we all have to use today. Absolutely necessary? No, but neither is a better Intake or carb or exhaust or camshaft. If all of those have been upgraded from 1970 specs to the latest technology, why leave out the ignition? How much can really be upgraded inside a box the size of a voltage regulator like the old factory ignition box? :dunno: My :2cents:

   
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Offline Supercuda

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Re: Got Hemi back from shop
« Reply #13 on: September 09, 2008 - 06:43:36 PM »
This is about the way that this Hemi runs, not about all the cool things that have been done in the last 40 years to make the engine work more efficiently. In the October issue of Hemmings Muscle Machines, there is, in addition to the very cool article about the new Challenger, an excellent article about diagnosing problems on an engine. It is called: "The Lost Art of Diagnosing Engine Problems," and is written by the very knowledgeable and experienced Ray Bohacz. It describes the way to properly attack a running issue, and covers a lot of the basic things that many of us seem to forget to check. I cannot argue strongly enough for a careful and thorough diagnostic routine. This article says everything that I would like to say every time there is a running problem with a vehicle, and people call me for help. Often, the real problem is simple, and would have shown up within the parameters of a proper diagnostic routine. Fix the problem first, and then think about upgrading parts. I have no problem with my ignition system due to low voltage (I have checked, and it is indeed 6 V), and if the voltage to the coil needs to be increased for better performance, then there is a problem with the coil or another component of the secondary portion of the ignition system. I have never said that there are no improvements to the wheel, just that the wheel worked just fine without them. I have seen the results of the DUI testing on the 360, and was impressed. I am sure that the major improvements came from the closer tolerances and better quality control lavished on the DUI part, and not due to any greatly improved circuitry or technology applied to the rest of the system. The GM HEI is a fine setup, but is just that- a GM design. I will keep my MOPAR as MOPAR as I can, because of my principles, not because I am a stick in the mud. Where there are shortcomings in the stock system, I never just "deal with it," but try to figure out a solution that does not result in reinventing the wheel. The major improvement made to the HEI system, as done by DUI, is a better dwell control in the ignition module. Basically, the DUI on a MOPAR is just a neat way to package the best that GM or MOPAR could offer, for those of us that want a less cluttered engine bay. The aftermarket controllers are great, but unnecessary in a basically stock, or near-stock application. It then becomes a matter of personal preference.

Offline Chryco Psycho

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Re: Got Hemi back from shop
« Reply #14 on: September 09, 2008 - 07:36:55 PM »
while I agreee that ign systems have imporved if the system is firing the plugs properly a whole lot of $$ is not going to improve power , basically the dist just sends a signal to the box to ground the coil , the newer dist can be easier to adjust the curve but the Mopar is a good stable system , the same goes with the ign box , all it does is switch the coil ground on & off so as long as the switch is fast enough you are good to go , the old Mopar boxes can be limited in the switching speed which is why they had better quality ones for higher RPM use
MSD is usually $450 + where the Mopar system is 1/2 that , the MSD still requires chip to limit RPM unless you get the Digital which the local speed shops tell m e is unreliable , the Mallory & Crane boxes are at least reasonably priced & have digital / dials for rev limiting

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