I have been running a 78 or so 318 electronic ignition dist in my RedRam for years. My intake mani is in bad shape so I shrugged off low speed miss as a vac leak. I have recently put in a new dist and the low speed miss was the same but has since slowly gotten worse. I can get rid of almost all of it by increasing the plug gap. I am up to .065 now. I will probably go higher. I am happy if the engine is happy but I don't understand the big gap. It runs poor at .045, worse at .035 and almost not at all at .025. I am worried something is going out. The only other thing is the amplifier or the resister. I can't figure out why it would rather jump the big gap than the smaller? It has new plugs, recent valve job,and the carb has been gone thru. It gets excellent gas milage and runs fine at other than real low speeds. Thanks!
chrysler electronic ign. was designed for a wider gap u should have a .060 to .070 plug gap with a .010 to .012 gap in the dist. the reason it needs a wid gap is because the voltaage is much higher it needs to jump farther to get the full potential of the spark
IIRC, the oem manual calls for 0.008" between reluctor and star wheel and it must be checked with a non-metallic gauge. .
I've had multiple 340s and 440s with Chrysler electronic ignition and ran the plugs at the stock gap and it worked OK, but you've got me thinking about increasing the gap on the next set of plugs I install to see if it helps.
I seem to remember that Chrysler electronic ignition was a bit fussy about having a stable, minimum voltage to operate properly. Years ago their ignition conversion packages listed a specific electronic voltage regulator by part number that was to be used when upgrading. Don't remember a spec for minimum voltage, but you're not running this with an old electro-mechanical voltage regulator by any chance, are you?
Chrysler ignition is NOT designed for large gaps. Your miss is because the engine is lean. A large gap combats that. GM HEI ran large gaps to stop a lean roll and a low speed problem during the days when automotive designer thought running lean reduced emissions. That has since proven false. Electronic igniton is not good because it is electronic and has some magical quality not available in conventional points ignition. It is good because it never goes out of adjustment. No points burning or rubbing block wear. Once you set it up it stays the same and other then timing chain wear the timing will remain the same forever. Points would last about 6 months to a year and probably you could reset some cars every month in truth. The output from a Chrysler ignition is not particularly different, points or electronic, speaking for a spark strength view. It is however a very very good system. Dr Jacobs in his book Optimizing Ignition System tells of subbing a standard Chrysler ign module for a Exotic sports car electronic system in a jam with no problems and said he had tested the LX101 Standard Ign Products box to 10,000 RPM. I use them in all my cars. race or hot street. There is no black magic no bugaboo , just a good sound solid performing ignition that will make many three letter and such exotic systems sold by the hotrodding BSPs look foolish. I like to use the accel small round yellow or chrome coil with mine. Easy to hook up from memory even . Only 4 wires. (fifth is no longer used.) don
Here's a couple of links you might want read that mention the need for using the electronic voltage regulator. At least compared to the older electo-mechanical regulator it provided higher and more stable output, especially at lower engine RPMs. http://www.forabodiesonly.com/mopar/showthread.php?t=6979 http://www.fourforty.com/techstuff/ignition.html Unfortunately it doesn't specify the exact requirements for the Mopar electronic ignition. And I don't know how it compares to the output of an internally regulated DelcoTron. But it might be food for thought while you're trying to sort things out. If the engine is mechanically sound and in a proper state of tune I can't imagine that increasing plug gaps is going to cure anything. A .035 to .045 gap should be sufficient on a street driven engine if the rest of the ignition is up to snuff. Increasing the gap just adds more resistance to the secondary ignition circuit and puts more strain on the ignition system, which may already be a bit stressed out. Maybe it's time to figure out if you really have a vacuum leak or not and fix the root problem. And not surprisingly, Dolmetsch beat me to it while I was copying and pasting links for you. Couldn't have said it better myself.
I agree it seems lean. I have tried riching the idle and pulling the choke. No difference. What gap do you use? It only misses at very light throttle and 40 mph and below. It kind of surges.
I don't think I have a vac leak. I have just done a valve job and I did a good inspection of the manifold and carb. The gaskets did not show not sealing anywhere and I went thru the carb with a through cleaning and new gaskets. No PCV or other leak sources I can find. Elec wiper.
That ain't the first time I got slapped bench racing, but I'll take it in stride. It was late and I posted that right after dumping my beer on the key board.
Thank you for sharing your knowledge and trying to help. I have tried everything I can think of. I just can't figure this out.
If you have access to a tail pipe sniffer then check then you can verify/deny a lean condition and move on to the next item on the list. A chassis dyno would be nice.... At low speed, part throttle (depending on the exact carb setup) you are likely still running on the idle circuit (assuming rpm is under 1500 or so). .
This is mostly true, except for the part about Electronic Ignitions not being different than Points form a spark strength view. When the circuit to the coil opens and magnetic field collapses creating the voltage spike that sends the current from the coil, through the spark plug wire and causes the plug to fire, the stronger and faster the circuit opens also determines the strength of the spark. Electronic switching does this in nano-seconds which is must faster than points can in a perfect world. As the points wear, and the gap changes, along with condenser degradation this time to open the circuit becomes longer and the spark becomes weaker. Electronic ignitions can supply up to 5 times more initial energy to the coil resulting in more spark energy - ie, a stronger spark. The other big feature that electronic ignitions can offer is Adaptive Dwell like PerTronix's patented design. By constantly monitoring the load on the coil and the RPM, the dwell is always changing to allow the optimum charge time in the coil for maximum spark voltage when needed. Aside from things like point bounce and condenser overload, fixed dwell times are one of the reason that point ignitions can mis-fire at higher RPM. You were dead on about the large plug gaps and lean mis fires. The GM H.E.I. (a system with many inherent flaws, but that is for another discussion) was developed to overcome lean issues caused by EPS mandated lean mixtures for emissions that created it's own problems.
I will try another carb. I have an extra. I am running the exact same carb on my 276 Flat motor. It shows none of the problems. The carb is off a 54 Buick.
-A slight difference on the 4 post and 5 post ign. box. The 5 th plug is a ground. If you have a 4 pin box make sure you have a good ground on the box itself. And a ground to chasis from body. One other problem on the dist is the shaft will warp in long useage. To check for bent dist shaft just remove dist cap and rotor the watch the gap on the reluctor . If it changes R and R the dist or tear it down and straighten shaft. On other thing a lot of times a intake that is not tight will cause a problem like you stated. I hope this helps a little.. Bobby..
Yup more gap helps cover a lean issue..... we used to widen the gap on the new cars back in 1975 when I worked at the dealership... helped them run better
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