350 no fire on 4 cylinders.
Thread Starter
3rd Gear
Joined: Aug 2020
Posts: 3
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350 no fire on 4 cylinders.
when my 72 runs like **** I can pull every other plug wire off the cap and notice no difference in running but when i put the wire back on I can hear the spark jump.Have a msd6a on it. Any suggestions? 350
Pro
Joined: Apr 2012
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From: USA
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Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
If it is an old 6AL......look on the side and see of the cylinder disconnect wires are corroded or cut......these are clipped when running a 4 or 6 cylinder......these are on the soft touch disc on the side of the unit.....
Jebby
Jebby
Last edited by Jebbysan; Aug 17, 2020 at 09:07 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
If the 4 non-firing cylinders are all on one side of the engine, problem is with the carb or the intake manifold / gasket. Otherwise, distributor cap is the likely culprit.
(Assumed that you were already checking out the spark box...)
(Assumed that you were already checking out the spark box...)
Le Mans Master
Joined: May 2005
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From: Central Maryland
Live well,
SJW
Last edited by SJW; Aug 19, 2020 at 10:11 PM.
Le Mans Master
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Cruise-In IX Veteran
Le Mans Master
Joined: Aug 2017
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From: Cool Northern Michigan
Yup. This engine either has a fuel-delivery problem on one primary venturi, or a large vacuum leak that's only leaning out one plenum of the dual-plane intake manifold. It's almost certainly something clogged in the carburetor. A rebuild of the carb should solve the problem.
Live well,
SJW
Live well,
SJW
Le Mans Master
Joined: May 2005
Posts: 7,319
Likes: 2,240
From: Central Maryland
"I can pull every other plug wire off the cap and notice no difference in running but when i put the wire back on I can hear the spark jump."
So it's missing on every other cylinder and he's getting spark to the dead cylinders.
It's either running on 1, 4, 6 & 7 and missing on 8, 3, 5 & 2, or it's running on 8, 3, 5 & 2 and missing on 1, 4, 6 & 7. He hasn't told us which four are missing, but that'll be the clue to which side of the carburetor or intake will have the fault. My bet's on a clogged jet or passage in the carb.
Live well,
SJW
