Msd 7?

GTX JOHN · 10-22-2010, 04:58 PM

would look at borrowing another coil and making a pass with it.....especially with one of the newer style MSD coils

FED 387 · 10-22-2010, 05:33 PM

As far as the coils go check the resistance between the positive coil terminal and the neg coil terminal resistance should be less than about .016 or so then check the resistance between the positive coil terminal and the coil tower that should be about 30 ohms---if either of those numbers are off the coil is bad---if the numbers are close then you have problems elsewhere---also check the air gap at the pick up and make sure that the magnets in the flipper wheel are not loose too as well as the pickup wiring----do you have ANY other wires running in close proximity to the pick up??? Those pick up wires should be shielded you can get some stuff at most electronics stores to do that helps prevent any stray signals from interfering with the signal from the pick up to the MSD box---Comp

FED 387 · 10-22-2010, 05:38 PM

Also like GTX said borrow another MSD coil see if that solves the problem---Are you using a MSD 7 that is set up for the correct engine you are using?? By that I mean a 7220 for an 8 cyl engine or a 7224 for a 4??? You cannot use a box for a 8 on a 4 or 6 and vice versa it will not function properly

Rich Biebel · 10-22-2010, 05:57 PM

I had an MSD 7al 2 in my Firebird Stocker. One day at the track I started to get misfiring over about 6000rpm and the tach was jumping around when it misfired. This engine had a crank trigger and most everything but the MSD box was new. I borrowed my friends identical 7al2 and the car ran perfect...no missing. I sent my box to MSD.....they said they could find nothing wrong with my box. I swapped it back into my car one day at the track....same problem returned...missed badly over 6000 and tach was shutting off when it missed....removed it and reinstalled my friends box same day....no missing. I bought a Digital 6 and matching coil and installed that. That box failed for the person who bought that car and it was no more than 2 years old when it failed. Probably got wet sitting out in the rain from waht I was told....I used to think MSD was the best ignition and boxes either worked or they didn't. I bought an MSD ignition box tester that they sell.......it allows you to fire the box without the engine running......pretty handy for testing a lot of things that are rpm triggered and to see the spark energy at any rpm. If I have a box I am not sure about...I'd replace it and MSD is not the only brand out there...Mallory has a good reputation for reliability.....

If you have an MSD distributer with mag pickup in the distributer your problem could be the small module in the distributer........I have a friend who chased a miss for months and that is what his problem truned out to be.....

rod · 10-22-2010, 07:43 PM

1. i was unaware that there were different boxes for different cylinders. will check that.
2. this chevy has a mallory uniliite for trigger.
3. the tach needle does, in fact, moooove towards 0 when it pops.
4 i have raced this car/engine for 37 years and never had it pop at the top of a gear. it does have an 8K top rpm chip, so it shouldn't be that as 7K is as high as i ever push it.
5. i have 2 different coils i can sub in. will try that also.
6.i am so MAD i could scream !!!!!!!!!!!!!!!!!!!!!!!

guys thanks for all the suggestions
rod in AZ

10-22-2010, 04:58 PM	#1
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,733 Likes: 2,803 Liked 2,486 Times in 697 Posts	Re: Msd 7? would look at borrowing another coil and making a pass with it.....especially with one of the newer style MSD coils

10-22-2010, 05:33 PM	#2
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,422 Likes: 529 Liked 333 Times in 180 Posts	Re: Msd 7? As far as the coils go check the resistance between the positive coil terminal and the neg coil terminal resistance should be less than about .016 or so then check the resistance between the positive coil terminal and the coil tower that should be about 30 ohms---if either of those numbers are off the coil is bad---if the numbers are close then you have problems elsewhere---also check the air gap at the pick up and make sure that the magnets in the flipper wheel are not loose too as well as the pickup wiring----do you have ANY other wires running in close proximity to the pick up??? Those pick up wires should be shielded you can get some stuff at most electronics stores to do that helps prevent any stray signals from interfering with the signal from the pick up to the MSD box---Comp

10-22-2010, 05:38 PM	#3
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,422 Likes: 529 Liked 333 Times in 180 Posts	Re: Msd 7? Also like GTX said borrow another MSD coil see if that solves the problem---Are you using a MSD 7 that is set up for the correct engine you are using?? By that I mean a 7220 for an 8 cyl engine or a 7224 for a 4??? You cannot use a box for a 8 on a 4 or 6 and vice versa it will not function properly

10-22-2010, 05:57 PM	#4
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: Msd 7? I had an MSD 7al 2 in my Firebird Stocker. One day at the track I started to get misfiring over about 6000rpm and the tach was jumping around when it misfired. This engine had a crank trigger and most everything but the MSD box was new. I borrowed my friends identical 7al2 and the car ran perfect...no missing. I sent my box to MSD.....they said they could find nothing wrong with my box. I swapped it back into my car one day at the track....same problem returned...missed badly over 6000 and tach was shutting off when it missed....removed it and reinstalled my friends box same day....no missing. I bought a Digital 6 and matching coil and installed that. That box failed for the person who bought that car and it was no more than 2 years old when it failed. Probably got wet sitting out in the rain from waht I was told....I used to think MSD was the best ignition and boxes either worked or they didn't. I bought an MSD ignition box tester that they sell.......it allows you to fire the box without the engine running......pretty handy for testing a lot of things that are rpm triggered and to see the spark energy at any rpm. If I have a box I am not sure about...I'd replace it and MSD is not the only brand out there...Mallory has a good reputation for reliability..... If you have an MSD distributer with mag pickup in the distributer your problem could be the small module in the distributer........I have a friend who chased a miss for months and that is what his problem truned out to be..... __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 10-22-2010 at 06:02 PM.

10-22-2010, 07:43 PM	#5
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 315 Likes: 0 Liked 20 Times in 15 Posts	Re: Msd 7? 1. i was unaware that there were different boxes for different cylinders. will check that. 2. this chevy has a mallory uniliite for trigger. 3. the tach needle does, in fact, moooove towards 0 when it pops. 4 i have raced this car/engine for 37 years and never had it pop at the top of a gear. it does have an 8K top rpm chip, so it shouldn't be that as 7K is as high as i ever push it. 5. i have 2 different coils i can sub in. will try that also. 6.i am so MAD i could scream !!!!!!!!!!!!!!!!!!!!!!! guys thanks for all the suggestions rod in AZ

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