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spark plug gap increase? |
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ddfarm 
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Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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 Topic: spark plug gap increase?Posted: Nov/19/2014 at 3:06pm |
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Just put in a petronix ingnition and coil in my stock 304. didn't want to fool with points. I by-passed the resistor wire and the car runs good. My question is, should I increase the gap of the stock plugs to get a better performance
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cindys1971
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JERSEYJOE
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Joined: Oct/23/2008 Location: TUG HILL NY Status: Offline Points: 1716 |
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Posted: Nov/19/2014 at 3:20pm |
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With that I would go to .040
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1985 J-20 PLOW TRUCK
1977 CJ 7 360 T-18 D 300 1970 AMX ex-SCCA car SPEED COSTS MONEY HOW FAST DO YOU WANT TO GO? |
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69 ambassador 390
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Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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Posted: Nov/19/2014 at 9:15pm |
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I agree. .040 would work well with the stock coil. Any more and the extra current may heat up the coil and shorten its life. If you went to the matching Pertronix coil, you could run .050 but that would only put more load on the cap, rotor, wires and plugs. If you plan to run lean for mileage or boost it the it would be worth it. I think I would go to the Pertronix coil to match the points eliminator unit better and keep the gap reasonable.
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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Wrambler
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Posted: Nov/20/2014 at 8:22am |
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With an aftermarket coil I split the difference and run .045"
It allows a little room for wear and I haven't had any issues at all with it. I generally check the gap every now and then. I don't drive it enough to cause any concern about wear during the warmer months. The plugs and wires are so old they a both Splitfire brand! When I do take them out I'm going to build them a little museum exhibit! |
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Wrambler
69 AMC Rambler 4.0L, 5 speed 2015 Grand Cherokee Limited 2019 Chrysler 300 |
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ddfarm
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Joined: Nov/23/2009 Location: Virginia Status: Offline Points: 315 |
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Posted: Nov/20/2014 at 10:22am |
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Actually I am running a Flame Thrower coil from Petronix so I think I will try increasing the gap to .045. I also have very good wire on this motor.
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cindys1971
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gwryder
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Posted: Nov/20/2014 at 10:59am |
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I put a Petronix II with a Flame Thrower coil (1.5 ohm). I wired 12 volts direct to the coil and regapped the plugs to .040. I didn't notice any difference in power. I think I could go with more gap, but .005 increase was enough for a start.
John
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John
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ddfarm
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Posted: Nov/20/2014 at 3:17pm |
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I am going with the .045 and see what happens. Will increasing the gap create a difference in gas mileage. I do not drive this vehicle to get good gas mileage! but it would be nice to know what this increase will do.
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cindys1971
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6PakBee
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Posted: Nov/20/2014 at 6:42pm |
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Just remember that spark gap controls the system voltage. Wider gaps require more voltage to establish an arc. The greater voltage with a wider gap increases the stress on all of the components in the system, wires, cap, coil, Go slow. If you hit the limit on some component, you many get misfiring/cross-firing, and all the other undesirable results of too much gap.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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Boris Badanov
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Posted: Nov/21/2014 at 7:24pm |
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IMO if the fire is getting lit then there is nothing to be gained by
any changes other than timing. If the fire is intermittently failing to light then more hotter spark is a good thing.6PackBee is correct, but it is the total gap that determins voltage. That is the gap in the distrubiter added to the plug gap and any resistance in the wires. The bigger the gap the vigher the voltage, but a drop in amperage. Set it where it runs best. There is nothing to gain by getting creative here.... Start cross firing and there is a LOT TO LOOSE! |
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Gremlin Dreams
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ddfarm
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Posted: Nov/22/2014 at 5:15am |
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With the system that I have (petronix ignitor and petronix coil, performance 8mm wires but standard dist cap), do you think that a .040-.045 is too wide?
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cindys1971
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