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> Increase sparkplug gap with CDI ignition box??, for /4 motors :)
Mueller
post Jun 14 2005, 01:57 PM
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taking tommorow off from work to hopefully "fix" my ignition and fine tune the fuel injection.....according to what I can find, the stock sparkplug gap should be .7mm (.028") for my 1.8 motor.

I thought that with the CDI such as a Mallory or MSD, I could open the plugs up to .050-.060" (according to MSD documents)

anyone have any real world experiance with this??

thanks
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ArtechnikA
post Jun 14 2005, 02:09 PM
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i use 0.046" with my Crane HI-6. seems to work just fine.
i selceted 0.046 because in my feeler gauge set, there is a 0.022 and a 0.024 next to each other, and that's as big as it goes.

probably to be scientific, you'd increase it 0.001 at a time until you saw a jump in HC at peak cylinder pressure. i just picked an arbitrarily large size i could easily measure and decided it was good enough.

the spark plugs you use will make a small difference, at the limit, and you'd better have good spark plug wires.
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DNHunt
post Jun 14 2005, 02:14 PM
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Mike

I used a .048 gap with a MSD 6A. I also used a W5CC plug.

Dave
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Joseph Mills
post Jun 14 2005, 02:26 PM
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QUOTE (Mueller @ Jun 14 2005, 01:57 PM)
I thought that with the CDI such as a Mallory or MSD, I could open the plugs up to .050-.060" (according to MSD documents)

anyone have any real world experiance with this??

Mike,

I have a mallory hyfire in a 2.0 with carbs and I went to .040 and then to .045 and have left it there.
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john rogers
post Jun 14 2005, 02:31 PM
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Well, when I put in the MSD system in the race car, I checked with MSD and they said to use .055 taking in consideration the carbs (Weber 48s), cams (906), coil (MSD), plug wires (9mm) and octane (100) of the gas I plan to run. They said if it is too small you loose power because of less burn and if too big the spark looses energy jumping too much gap and the burn happens too late. I also run an A/F mixture of 12:1 at wide open and so far .055 has worked well.
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Joe Ricard
post Jun 14 2005, 03:07 PM
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QUOTE (john rogers @ Jun 14 2005, 12:31 PM)
Well, when I put in the MSD system in the race car, I checked with MSD and they said to use .055 taking in consideration the carbs (Weber 48s), cams (906), coil (MSD), plug wires (9mm) and octane (100) of the gas I plan to run. They said if it is too small you loose power because of less burn and if too big the spark looses energy jumping too much gap and the burn happens too late. I also run an A/F mixture of 12:1 at wide open and so far .055 has worked well.

Now see there... Here is some real world experience with a who said and why.
I also run a gap of .045 which seems to work for me. have't given much thought to it but now I got an idea. (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif)
Again I wish I had a dyno and wide air fuel meter.. The butt dyno is not calibrated for this kind of tuning.
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ArtechnikA
post Jun 14 2005, 03:12 PM
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QUOTE (Joe Ricard @ Jun 14 2005, 05:07 PM)
Now see there... Here is some real world experience with a who said and why.

yes, it all sounds real scientific, but you have to understand that MSD always tells everybody to use 0.055" (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
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redshift
post Jun 14 2005, 03:24 PM
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QUOTE (Joe Ricard @ Jun 14 2005, 05:07 PM)
I also run a gap of .045 which seems to work for me. have't given much thought to it but now I got an idea. (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif)
Again I wish I had a dyno and wide air fuel meter.. The butt dyno is not calibrated for this kind of tuning.

I'll put my mouth over the pipe, while you redline it.. I can taste to a resolution of 0.00681 p/pm.


M
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john rogers
post Jun 14 2005, 03:46 PM
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Hummm, MSD did tell to go to .065 and 2 more degrees of total advance if I run 110 leaded which we do at some of the vintage races??!!
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J P Stein
post Jun 14 2005, 10:43 PM
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You need more than a CD ignition. You also need a high power coil to jump a big gap. Your wires need to be top notch, also.
"Normal" coils won't cut it over about 5-6K rpms. I use the MSD Hi Vibration jobbie cause you can mount it at any angle.
.045 here.
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Joe Ricard
post Jun 15 2005, 07:03 AM
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QUOTE (redshift @ Jun 14 2005, 01:24 PM)
QUOTE (Joe Ricard @ Jun 14 2005, 05:07 PM)
I also run a gap of .045 which seems to work for me. have't given much thought to it but now I got an idea. (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif)  
Again I wish I had a dyno and wide air fuel meter..   The butt dyno is not calibrated for this kind of tuning.

I'll put my mouth over the pipe, while you redline it.. I can taste to a resolution of 0.00681 p/pm.


M

You need help!
Or more (IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)
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