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07-23-2005, 01:33 PM
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CC Member
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Join Date: Apr 2004
Cobra Make, Engine: Superformance 351W
Posts: 63
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Not Ranked
Spark Plug Gap
To all:
I have 351w with Edlebrock Performer RPM heads and Victor Jr. intake and running Duraspark 2, What is the plug gap? I have had answer's .035, .040 yet another .050 - all by people that stand to profit from a tune up. "their own personal economy stimulator" I bought the ford manual's on the block and the info wasn't in there, I guess that info was on a sticker under the hood. It probably does not apply anyway cause of points
So what is the GAP???????????
Thank you
GWC
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07-23-2005, 06:39 PM
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CC Member
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Join Date: Aug 2004
Location: SE Wisconsin,
Wi
Cobra Make, Engine: Arntz/SBC/Jag
Posts: 1,033
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Not Ranked
There isn't really one right stock answer, for optimnum results you need to experiment some.
Same goes even for spark plug heat range. As you start modifying the engine and using different ignition components there's no answer in a book.
BUT, with a healthy ignition system, as a base starting point, if you have less than 10.5:1 compression, try .050 to .060.
Between 10.5 and 13:1 try .040 to .050.
If your ignition isn't so powerful you will need to go with a slightly smaller gap.
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07-24-2005, 10:15 PM
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CC Member
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Join Date: Apr 2004
Cobra Make, Engine: Superformance 351W
Posts: 63
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Not Ranked
Yetiman,
Thank you for reply. As i stated i'm running Duraspark 2, which probably leans toward spark plug gap .050-.060 I wonder what the symptom's of a bad gap would be, low RPM stumble, high RPM's ok??
Thank You
GWC
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07-24-2005, 11:56 PM
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CC Member
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Join Date: Aug 2004
Location: SE Wisconsin,
Wi
Cobra Make, Engine: Arntz/SBC/Jag
Posts: 1,033
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Not Ranked
A wider gap (bigger spark) generally will give more complete combustion and easier starting, better low RPM operation.
If you start going wide, you have to make sure you have a powerfull enough ignition to keep up at higher RPM and bigger fuel loads.
Generally a bit bigger is better.
I have a small block running 10.5:1 with well ported heads and a 284/294 cam. I'm using an MSD capacitive discharge box with a Crane Cams Hall Effect unit in place of the points.
I run the engine to 6600 rpm regularly, and have settled into a .055" gap which seems to work well and solved fouling problems I had using smaller gaps with the original points setup.
When I went to the MSD/Crane and wider gap setup my fuel milage improved signifficantly (like 35% or better) than the setup the engine had when I bought it (.030" gap and points).
Much better driveability and power as well.
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08-01-2005, 01:40 PM
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CC Member
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Join Date: Apr 2004
Cobra Make, Engine: Superformance 351W
Posts: 63
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Not Ranked
Yetiman,
Well after fiddlin & diddlin with the plug gap, the best gap for this engine is .045. After trying .035, .040, .050 and .055. Best all around gap was .045, the difference was very noticeable.
GWC
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08-01-2005, 01:43 PM
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CC Member
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Join Date: Aug 2004
Location: SE Wisconsin,
Wi
Cobra Make, Engine: Arntz/SBC/Jag
Posts: 1,033
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|
Not Ranked
Glad to se you got it sorted out!
A lot of times a little experimenting goes a long way, and makes it worth the trouble.
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