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Author Topic: Which distributor cap to use with MSD 6AL?  (Read 1504 times)

Offline elevenssc

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Which distributor cap to use with MSD 6AL?
« on: July 25, 2010 - 01:41:48 PM »
I'm getting some misfiring/cross firing on my 340 4-spd 70 Cuda at 3000 rpm.  It happens in all gears and varies with engine load (worse in 1st and not as bad in 4th).   The cap and rotor are new from Summit (I think they are Accell if I remember right).

I'm guessing it may be cross firing in the dist cap and I'm curious if there is a better dist. cap/rotor out there.  Anyone else run into this same problem? 

Thanks,

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Which distributor cap to use with MSD 6AL?
« on: July 25, 2010 - 01:41:48 PM »



Offline 422STROKER

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Re: Which distributor cap to use with MSD 6AL?
« Reply #1 on: July 25, 2010 - 06:42:37 PM »
I'm on my 3rd cap and rotor set in the last 3 years, I've been getting the Autozone premium cap, has Brass contacts and a vent.  The contacts seem to take a beating(after a year(5K miles) but it seems to fire fine.  Maybe there is something else going on?  Have you checked for proper alignment of rotor to to cap  terminals?

Tom

Tom
12.77 @ 108.87 15" Street Drag radial tires 3.23 gear

Offline ShelbyDogg

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Re: Which distributor cap to use with MSD 6AL?
« Reply #2 on: July 26, 2010 - 11:54:53 AM »
Try reversing the pick-up wires from your pickup to MSD box.  Re-time the car.

This should fix you up if it isn't your wires.
Rob

Stop staring at my avatar!  3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...

Offline elevenssc

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Re: Which distributor cap to use with MSD 6AL?
« Reply #3 on: August 02, 2010 - 08:59:24 PM »
Switched wires + Re-timed Car = Miss gone...

Thanks ShelbyDogg...

Offline ShelbyDogg

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Re: Which distributor cap to use with MSD 6AL?
« Reply #4 on: August 02, 2010 - 10:16:11 PM »
Ah....  Magnetic pickups and sine waves..... Rising edge or falling edge.  Makes me want to put in hall sensors....  I'm babbling now.

Aren't you glad that you didn't buy a bunch of caps and rotors?  I'm glad that I clicked on your CAP question and could help out.
Rob

Stop staring at my avatar!  3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...

Offline UKcuda

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Re: Which distributor cap to use with MSD 6AL?
« Reply #5 on: August 04, 2010 - 04:32:04 PM »
Ah....  Magnetic pickups and sine waves..... Rising edge or falling edge.  Makes me want to put in hall sensors....  I'm babbling now.

Aren't you glad that you didn't buy a bunch of caps and rotors?  I'm glad that I clicked on your CAP question and could help out.

That was some sharp-shooting diagnosis there  :worshippy
'72 'cuda

Offline ShelbyDogg

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Re: Which distributor cap to use with MSD 6AL?
« Reply #6 on: August 04, 2010 - 06:48:08 PM »
That was some sharp-shooting diagnosis there


Not really.  As you can see I told him exactly what to do without guessing.
That means that have spent a little time fixing the same problem on my fuel injected cars. All VR (variable reluctor)  magnetic pickups are the same, putting out an AC sinewave. You Ignition box pick up on this signal and determines when to send a spark.  Some of those Mopar Orange boxes also needed the pickup wires reversed due to poor QC?

Here is a link to the Megasquirt Manual that explains the "trigger".  I have one of these running one of my 440s and the trigger is an option in the software.
Good reading if you follow the diagrams. You can see how triggering on the wrong edge can throw varied sparks between reluctor points and the car will have erratic timing.
http://www.megamanual.com/ms2/pickups.htm
Rob

Stop staring at my avatar!  3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...

Offline UKcuda

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Re: Which distributor cap to use with MSD 6AL?
« Reply #7 on: August 05, 2010 - 02:57:18 AM »
Not really.  As you can see I told him exactly what to do without guessing.
That means that have spent a little time fixing the same problem on my fuel injected cars. All VR (variable reluctor)  magnetic pickups are the same, putting out an AC sinewave. You Ignition box pick up on this signal and determines when to send a spark.  Some of those Mopar Orange boxes also needed the pickup wires reversed due to poor QC?

Here is a link to the Megasquirt Manual that explains the "trigger".  I have one of these running one of my 440s and the trigger is an option in the software.
Good reading if you follow the diagrams. You can see how triggering on the wrong edge can throw varied sparks between reluctor points and the car will have erratic timing.
http://www.megamanual.com/ms2/pickups.htm


I meant that your post was fast, uncomplicated and accurrate.

You must have thought I meant something else.
'72 'cuda

Offline ShelbyDogg

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Re: Which distributor cap to use with MSD 6AL?
« Reply #8 on: August 05, 2010 - 06:12:40 AM »
You must have thought I meant something else.

Thanks.
I know what you meant. I'm just saying I'm not the sharp shooter as it seems. I have just run into this problem many times and that is a common fix that many don't know about.
Rob

Stop staring at my avatar!  3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...

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Re: Which distributor cap to use with MSD 6AL?
« Reply #8 on: August 05, 2010 - 06:12:40 AM »