440 misfiring so time for some TLC...

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raven68
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440 misfiring so time for some TLC...

Post by raven68 »

Charger is now tucked up in the garage as the 440 misfire has become really noticeable now when running at a steady throttle. Accelerate and its fine. Idling is fine. So changed the distributor cap and rotor as the old cap was really bad. Had a new coil & ballast resistor a while back. Now going to change plugs, check the leads out, check the timing again and various voltages, etc. Its running with points that I will try re-gapping for now but my question here is probably best to upgrade to Pertronix or similar, but for roughly same cost I've noted in this section of the forum here that some have bought a complete new electronic distributor running with a 12v coil. Next step up would be an HEI distributor but I haven't searched that far yet. Any comments on what you've done or recommend would be welcome.

Carb is Edelebrock 1411 and I'll strip and clean that out at the same time.


Here's a picture of the old distributor cap. I'm embarrassed it got that bad and amazed it even ran at all...……!
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1970 Challenger 383 MMA-074
1968 Charger 440 MMA-80
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Dave999
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Re: 440 misfiring so time for some TLC...

Post by Dave999 »

you don't need to buy an HEI dizzy

you can use a standard 1970s mopar one with the magnetic pickup

run a 12 volts low primary ohms coil and given that fuel has changed considerably since the days of 2 4 and 5 star get a FBO advance limiting plate to reduce the mechanical advance in the dizzy so that you can run more initial advance with no extra total.

unless there is lots of gunk in your edelbrock or it leaks badly at the throttle shaft there isn't much in there to rebuild

its all springs and rods and weighted air flaps

Dave
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raven68
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Re: 440 misfiring so time for some TLC...

Post by raven68 »

Thanks Dave
I did wonder if the standard Mopar dizzy would be good enough seeing as there seems to be a fair few aftermarket electronic ones on offer, but I'll see what I can find.

Dumb question ref the low primary ohms coil... is that a coil that operates with the ballast resistor (as I already have a fairly new 1.5 ohm ballasted coil on the car)

what initial timing should I be running for a bog low compression 440 - the block decoded as a 75-79 and the iron heads are 76-78 open chamber with a 1971 stock intake (#3512501) if any of that makes a difference :? I had it set at 16 or 18 initial

Thanks again.
1970 Challenger 383 MMA-074
1968 Charger 440 MMA-80
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John
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Re: 440 misfiring so time for some TLC...

Post by John »

16 to 18 should be fine but make sure your not over the 35 mark all in.

Have you a vacuum can on the dizzy by chance? If so plug it up and disconnect it and give it another go.

And if you haven't done so already, check that you haven`t got any other little ports on the carb or the manifold open to the atmosphere.
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Dave999
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Re: 440 misfiring so time for some TLC...

Post by Dave999 »

low ohms 8 volt coil works with a ballast resistor

low ohms 12 volt coil works with HEI or late electronic ignitions

1.5 ohms coil with no ballast resistor will work with HEI provided it was a 12 volt coil designed with no ballast resistor in mind i have similar on mine

a "sports" coil designed to be used with no ballast resistor and points would usually be somewhere in the 1.8 ohms to 3 ohms range and be a 12 volt coil for no ballast.

a sports coil for use with a ballast would be used with a special ballast and the "sports" bit is catered for by the ratio of the primary and secondary as such they tend to be purchased as a pair.

initial advance

2 ways to go

set it up as per the book at something like 5 BTDC
start it
switch it off
add 2 degrees
start it

repeat process until it labours when trying to start be careful don't go too far it may kick back and smash your starter

knock it back 2 degrees.
lock it off

then check total

or stick it at 10 BTDC and see how it runs

add 2 and see if its better
you are looking for a sweet smelling exhaust at idle if it makes you cough and stings your eyes it needs just a smidge more

check you have no more than 34 total if you do you need to restrict in some way or run less initial and put up with the stink of petrol at idle

after you are finished plug the vacuum can back in. its great for cruise and helps with fuel consumption.

drive from low rpm to mid open throttle if it pings you need to remove some vacuum advance
this is done with an allen key down the vacuum pipe into the can on 50% of the dizzys, i cant remember which way you turn it.

it is done by swapping the can for the rest

the can will have a number on which is the degrees added at the dizzy. lower number lower degrees.

lots of people just disconnect it. you will use more fuel if you do there should be no suck on that pipe when the throttle plate is closed. i.e it plumbs into carb above the throttle plate
a small pipe below the throttle plate is for a choke vacuum feed to pull open the choke flap when the throttle is at various angles or gets plumbed into flaps in the snorkel filter on emissions equipment motors. or into the advance and air flow thingo on an ELB car


dave
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raven68
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Re: 440 misfiring so time for some TLC...

Post by raven68 »

Thanks Dave for all that information about the coils and getting the timing sorted. I'm not expecting overnight success here as I'll work my way slowly through the problems over the next couple of weeks but I will post up what I find & fix. Thanks again. :thumbright:
1970 Challenger 383 MMA-074
1968 Charger 440 MMA-80
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Steve
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Re: 440 misfiring so time for some TLC...

Post by Steve »

I did the HEI conversion on my Polara. MSD blaster 2 coil (no ballast resistor reqd), four pin GM style HEI unit mounted on an aluminium computer heat sink, standard Mopar electronic distributor....18/36 timing, plugged vac advance, all works fine :thumbright:
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raven68
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Re: 440 misfiring so time for some TLC...

Post by raven68 »

Just a quick update on the misfire. First thing was the spark plugs out. Pretty evident Cylinder 1 plug was fouled up, burnt out and not firing. Plug gaps were all less than 20thou and evident they were not getting hot enough on the Left bank. Right bank plugs were all a good colour. Changed all the plugs, gapped to 30thou (only had Champion RJ12YC on the shelf) and it started and ran fine, but retarded the ignition very slightly and it ran better. Will do proper timing light check today, but happy that it was just plugs. Will look at the electronic dizzy and better coil in the next few weeks.

Something is a bit odd with the ballast resistor though as it was 12v in and out with the engine off, so no apparent resistance. The coil is a Lumenition Megaspark 2 that requires the ballast, and I have had coils overheat and breakdown in the past, so a new electronic distributor with non-ballasted coil will be my preferred final solution to simplify things.
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1970 Challenger 383 MMA-074
1968 Charger 440 MMA-80
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Dave999
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Re: 440 misfiring so time for some TLC...

Post by Dave999 »

yeah they are a bit grotty aren't they

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Matt
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Re: 440 misfiring so time for some TLC...

Post by Matt »

Your ballast resistor is unlikely to be faulty. With the engine stopped and the ignition points open (or if electronic, distributor sensor not triggering), there's no complete circuit made through the resistor, and hence no current flowing in it.

Without current flowing through a resistor, there is no voltage drop across it. So your measurement of 12V each side is expected.

If you want to actually measure the effectiveness of the ballast, complete the ignition circuit by wiring the -ve side of the coil direct to earth and then measure the volts each side of the ballast. Don't leave the circuit connected this way for longer than necessary or stuff will start getting hot due to the constant connection.
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raven68
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Re: 440 misfiring so time for some TLC...

Post by raven68 »

Final update / outcome. Searching on here I found another thread where someone bought / recommended a 12v coil & electronic distributor by Assault Racing. I dropped them an email, had a very quick reply pointing me to their Ebay store 'kmjperformance' and bought their packaged coil & distributor for $91 plus postage was $17 and prepaid VAT/import duty at $24.54. Distributor cap has male terminals so had to change the leads, but was going to do that anyway, so ordered a set of 8.5mm wires from Summit Racing. Swopped over the distributor, chopped out the ballast resistor and ran new 12v supply to the coil and fitted the new leads. Manually approximated the timing and it fired up. Sounds much sharper and more instant throttle response. Just got to fine tune with a timing light then back on the road this weekend. Very pleased with the kit. In the pictures you will see I marked #1 tip on the rotor in red paint plus the BTDC in the original firing position, as I then had to re-index the distributor body anticlockwise to the next firing point to allow more adjustment for advancing the timing.
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Assault Racing Distributor and huge coil - Note the extensive instructions with the distributor !!
Assault Racing Distributor and huge coil - Note the extensive instructions with the distributor !!
20190312_124422.jpg (83.8 KiB) Viewed 1816 times
First position of distributor, #1 & BTDC poistion marked - not enough room to advance the ignition enough as the vacuum canister fouled on the heater water pipe.
First position of distributor, #1 & BTDC poistion marked - not enough room to advance the ignition enough as the vacuum canister fouled on the heater water pipe.
20190319_105011.jpg (105.14 KiB) Viewed 1816 times
Distributor re-indexed on #1 cylinder to give more room for advancing the ignition clockwise if needs be.
Distributor re-indexed on #1 cylinder to give more room for advancing the ignition clockwise if needs be.
20190319_105125.jpg (106.08 KiB) Viewed 1816 times
Finally done - just got to tidy up the wiring and plug leads and job done
Finally done - just got to tidy up the wiring and plug leads and job done
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1970 Challenger 383 MMA-074
1968 Charger 440 MMA-80
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morgan
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Re: 440 misfiring so time for some TLC...

Post by morgan »

Nice. My MSD all in one is a similar thing. 12v in one end and forget about it.
Cant get my vac advance to work at all though - blocked it off in the end. Soon as you connect it up it bangs , shudders, backfires - the works !

Good job. :thumbright:
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