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09-25-2008, 08:25 PM
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CC Member
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Join Date: May 2008
Location: San Jose CA,
CA
Cobra Make, Engine: SPF_R_/BRG/FRBoss302/327CI/FordEFI/Under_Car_Exh/
Posts: 2,523
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Not Ranked
Spark Plug Gap- Poll
I had the idea to open up some basic topics to help the newbies / non-wrench turners to care for their cobras.
In so, getting a sense of SBF spark plug gaps, and what they run in.
-- in my experience;
with a points ignition systems in small block ford, a plug gap of .032 to .035" is fucntional for a stock distributor (points type) and a stock coil.
if you add a magnetic trigger (pertronix) to the distributor and a hotter coil that can allow you to open up the spark plug gap to .035-.038"
If you run a duraspark or HEI you can open the gap to .045-.049 depending on camshaft, carb and timing.
With an MSD or other type of capacitive (multi) spark discharge box, that can avail you to open the gap up .044-.059 depending on many factors.
In my experience, the narrower the plug gap - the smoother the idle can be, but this will take away from power at upper rpms. also there can be to-wide of a gap causing the engine to have a rattly idle and not feel like pulling under load, like a miss' under load.
-- open for other to add their experience!
--Steve
__________________
Steve SPF 2734 MK3 / Brock Coupe #54- panavia.com
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09-25-2008, 08:48 PM
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CC Member
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Join Date: May 2004
Location: san jose,
ca
Cobra Make, Engine: spf #1723 427w
Posts: 421
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Not Ranked
MSD... .045 autolite 3924. 351/427w
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Greg spf 1723
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09-25-2008, 10:42 PM
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CC Member
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Join Date: May 2001
Location: California,
Ca
Cobra Make, Engine: NAF 289 Slabside Early Comp Car with 289 Webers and all the goodies. Cancelling the efforts of several Priuses
Posts: 6,592
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Not Ranked
MSD Distributor, MSD-6T box(Analog), UR5 NGK plugs @ .045 gap, 289 with 48 IDA's
__________________
Rick
As you slide down the Banister of Life, may the splinters never be pointing the wrong way 
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09-26-2008, 12:31 AM
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CC Member
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Join Date: Sep 2006
Location: Skjetten,
No
Cobra Make, Engine: Unfortunataly ; none
Posts: 333
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Not Ranked
Mallory unilite + Mallory 6A, NGK BCP6 @ .045 gap, 347 4 x 48IDF.
RS
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08-15-2009, 05:42 AM
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CC Member
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Join Date: Sep 2006
Location: Skjetten,
No
Cobra Make, Engine: Unfortunataly ; none
Posts: 333
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Not Ranked
New gap
.032 " (0,8mm) after reading high A/F (10- 12) and advice from a guy. Saying high compression pressures also should have smaller gap.
Does it work better? Time will tell.
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08-15-2009, 06:18 AM
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Senior Club Cobra Member
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Join Date: Dec 2001
Location: Shasta Lake,
CA
Cobra Make, Engine:
Posts: 26,599
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Not Ranked
.039/.042 with a Jacobs Pro Racing unit. But since Jacobs is no longer worth anything I will be changing to another type unit one of these days. Also stay away from he Platinum plugs if you do have a Jacobs.I tried them once and it ran crappy as they threw off the resistance readings.
Ron
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08-15-2009, 06:58 AM
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CC Member
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Join Date: Dec 2003
Location: Framingham,
Ma
Cobra Make, Engine:
Posts: 228
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Not Ranked
Hi,
Any high peformance engine with high compression, or power adder I tell to set gap at .035. It's best to get the spark than a misfire. Large plug gaps also burn out ignition wires. You can see wires that are like new but burned near the cap. They have a brown tinge to them.
Large plug gaps are for low performnce emissions engines.
I remember in the late 70's misfires at the rotor shorting to the distributor shaft....
Think of it as a .22 hit is better than a .45 miss...
__________________
Forte's Parts Connection
40 Pearl St
Framingham, Ma. 01702
fortesparts.com
508 875 0016
In 1993 Mike made the first conversion of a Ford Tremec to GM 5-speed. It bolts to stock bellhousings w/out an adapter. The FE Tremec, the Mustang adjustable quadrant are originals from Mike.
One of 12 Tremec Elite Distributors worldwide for: T-5, T-56 Magnum & TKO-500 & TKO-600 ,Midshifter, Frt shifter, offset Vette shifter.
Est: 1981 selling performance parts to build your dream car...
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08-15-2009, 12:40 PM
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CC Member
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Join Date: Feb 2007
Location: Raytown,
mo
Cobra Make, Engine: FFR Coupe SOLD.Current 66 Mustang
Posts: 962
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Not Ranked
Good info guys
__________________
  I agree Life is way to short to worry about gas milage.Other rides Crewcab Super Duty F350 Ford,Shlby Charger,66Mustang/Frankinstang,Chevy Van,KTM Dualsport,FFR Daytona Coupe SOLD... RUN N GUN 06,07,08,09 Hallet 09,
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08-20-2009, 11:09 AM
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CC Member
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Join Date: Sep 2006
Location: Skjetten,
No
Cobra Make, Engine: Unfortunataly ; none
Posts: 333
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Not Ranked
I'll install my new Denso- equivalent of NGK BCP7E at .035" this evening.
Maybe same thing will happen as when I changed from 5'ers to 6'ers?
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08-20-2009, 12:35 PM
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Senior Club Cobra Member
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Join Date: Nov 2003
Cobra Make, Engine: ERA #698 428 Toploader
Posts: 292
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Not Ranked
M.S.D. with E3 plugs, 3 tips, no gapping, no problem.
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08-20-2009, 02:32 PM
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Club Cobra Member
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Join Date: Nov 1999
Location: Salem,,
NJ
Cobra Make, Engine: ERA 289 FIA #2100 Rio Red Wimbledon White Stripes 302 stroked to 331 Webers Richmond Road Race 5 speed
Posts: 782
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Not Ranked
Mallory 6AL Autolite 3924 .040 gap
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 Snakebit
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08-20-2009, 06:40 PM
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CC Member
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Join Date: Aug 2007
Location: NE Oklahoma,
OK
Cobra Make, Engine: Fords
Posts: 544
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Not Ranked
Stock 289 Hi-Po , 10:1 compression w/ MSD Digital 6, Autolite 45's gapped @ .45
same as above with vintage Paxton (6 lbs. psi maximum), Autolite 45's gapped @ .28
Z. Ray
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'65 K code Mustang
'66 Galaxie 500
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08-20-2009, 09:15 PM
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Senior Club Cobra Member
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Join Date: Jan 2005
Location: saratoga,
ca
Cobra Make, Engine: Kirkham #185, Shelby Alloy 482; sold
Posts: 1,190
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Not Ranked
FE, Champion RC12YC, .032, 10:1, MSD.
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Dave
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