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Old 05-07-2007, 12:40 PM
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taps
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i have a 8.5 to 1 468 it is actually a blower motor without blower,has 825 demon carb,msd7al3ign.it is in a track car,my problem is when i go to track it runs fine for the first pass or 2 then it will start missing in high gear,i have a glide,i have tried carbs ,jetting,checked fuel pressure and volume,and plug wires.any ideas where to look next would be appreciated.
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Old 05-07-2007, 12:49 PM
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topsportsman1
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Whats the plugs gapped at?
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Old 05-07-2007, 12:52 PM
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plug gap is .040
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Old 05-07-2007, 12:58 PM
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Try .025 to .030
That should fix it

If it don't do you have the shielded wire going from the MSD box to the trigger pick up

The old wire had 2 wires the new replacement has 3
The 3rd wire is the ground
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Old 05-07-2007, 01:18 PM
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will try the plug gap,it is the old style wire without ground,also the car was set up with a crank trigger and i just plugged the wire into my msd dist that went to the 7al3,could there be a problem with that?
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Old 05-07-2007, 01:30 PM
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If your running the MSD dristributor without the crank trigger you should be Ok

But if you run a crank trigger you should do the upgrade to the 3 wire lead
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Old 05-07-2007, 01:57 PM
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i called the msd tech line and the guy there told me to run a ground wire from head to head and ground it to chassis,and increase plug gap to .050.that doesnot sound right to me if you increase gap wont that make resistance even higher.and in a tube chassis car motor plates i wouldnt think there would be ground problem.any thoughts on this advice.
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Old 05-07-2007, 02:02 PM
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Never mind him,he prolly just answers the phone,LOL
Close up the gap,you'll just have to trust me here

Keep us posted
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Old 05-07-2007, 02:11 PM
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THANKS! i will try your advice and let you know how it goes.
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Old 05-07-2007, 02:14 PM
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I would close the gap up like Tom suggested. I run the motor plate and midplate and do not have the separate ground wires to each head. If you are cranking the motor the ground should be fairly good.

But, you stated that it runs good and then after a few runs you start having the issues. How is your battery voltage? Are you running 2 batteries or 1? Are you running an alternator? If regapping the plugs doesn't help, you could possibly have low battery voltage. The MSD box takes a lot to run properly.

Does the problem go away the next time you bring the car out or do you have to change the plugs for the problem to go away? If you have to change the plugs for it to clear up, then the plugs could possibly be too cold. Have you changed the heat range after taking the blower off?

Bill M
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