MSD is weird!
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Elder User
Joined: Aug 2002
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From: CA
MSD is weird!
I took my MSD 6A out of my old Mopar (where it has worked great for 5 years) and put it in my '73 F-100 w/302. It still works great at speed and at idle Idles much better in fact), but often after coming down to idle from speed, the engine dies. It starts right back up fine. This never happened before swapping in the MSD.
I'm beginning to wonder if plug gap might be the problem. This is basically a stock engine, and MSD says that plugs in such engines can be gapped as high as .060" Seems high to me. I ran nearly stock gap in my Mopar and have nearly stock gap in this truck. I can't think of any other reason for this problem. Any ideas? Polkat
Fixin' is fun!
I'm beginning to wonder if plug gap might be the problem. This is basically a stock engine, and MSD says that plugs in such engines can be gapped as high as .060" Seems high to me. I ran nearly stock gap in my Mopar and have nearly stock gap in this truck. I can't think of any other reason for this problem. Any ideas? Polkat
Fixin' is fun!
Junior User
Joined: Oct 2002
Posts: 87
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From: Houston, Tx
MSD is weird!
i bought a 6al box, and installed it on my car... topend was good but it would run erraticly at anything except WOT the idol sucked and the car ran like crap unless it was floored... well i cant drive floored all the time and i got tired of it, to out of the car it came and in the garage it sits. 
Posting Guru
Joined: Feb 2002
Posts: 1,712
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From: Atlanta, Georgia, USA
MSD is weird!
You can run at least .060" gap with that box, and you can get away with a whole lot more, so that's not your problem. I've never heard of this, or why it would start only because you swapped the box in there, but seeing as how you have a points ignition, I'd suspect foulplay there before I looked at the MSD. It would be a great idea to go to a boneyard and grab an magnetic trigger distributor out of a 1975 or newer 302. That magnetic trigger distributor will perform much better, and it'll work great with the 6A box. The only problem with that is that you can't easily adjust the timing curve. I went ahead and got the Pro-Billet distributor, and that was a real nice pickup overall. I've heard of MSDs doing crazy things, but I'd encourage you to put a distributor in there that's a little more consistent, that way you can pinpoint the problem.
'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing
'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing
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Elder User
Joined: Aug 2002
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From: CA
MSD is weird!
[updated:LAST EDITED ON 20-Nov-02 AT 10:41 PM (EST)]It's hooked to a Duraspark distributor, not points. And it's not a major eratic problem, just an irritation sometimes when it cuts off (only when coming down to idle from high rpm. In fact, it idles perfectly...better then it did. At first I suspected it was probably some intermittend connection, but I wire professionally. I've had carbs cause this problem, but I doubt a fuel problem as I keep that in good shape. I now tend to think that the plug gap, which as you may not have read is only at .035, is the problem. I'll go ahead and open up the plug gap and see what happens. Thanks.
Laughing Gas
Joined: Apr 2001
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From: Elon, NC
MSD is weird!
Polkat, gonna throw my $.02 worth in. The gap shouldn't change anything as far as the truck cuttin off although you will should feel a little more ummmmmfhhhh with acceleration. When I built my 351W I started out with the plugs at the standard .040 gap and it ran great (MSD 6A and pro billet distributor). Opened them up to .060 and it felt even better, but I noticed a slight spark knock at WOT so I backed off to .050. It runs like a scalded dog now with no knock.
Ron
Ron
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From: CA
MSD is weird!
Thanks Ron. I'll give .050 a try and see what happens. Found the problem. I had used the original 3-wire connector to tap the MSD unit into. The connector was worn, and whenever I slowed down the force banged the connector into the distributor side, somehow making a temporary disconnect inside the connector. I cut the damn thing out and tapped the MSD wires directly to the distributors wires, and now it runs fine, but I will try the .050 gap to see if performance improves a bit! Polkat.
