Spark Plug Gap ?
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Elder User
Joined: Oct 2002
Posts: 573
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From: Medina, Tn.
Spark Plug Gap ?
I have always had my gap @ .42 per Haynes, Chilton and Mitchell but have read so much on this forum about guys using between .52 and .56. I do not have my sticker in the engine well so I am going by the books. What are the benefits to such a large gap and what are the draw backs ? Should I just keep it the same or what ?
Thanks guys.
Hope all had a safe New Year !
Thanks guys.
Hope all had a safe New Year !
Senior User
Joined: Nov 2003
Posts: 348
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From: Indiana
My Chiltons Truck Manual say's .044, but I guess .042 is close enough. The only way to find out if a larger gap will help, is to try it. Ignition system needs to be in good shape though (wires, cap. coil, etc).
Steve
Steve
Tuned
Joined: Mar 2002
Posts: 250
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From: Grants Pass, OR
Do you have the stock coil or aftermarket. I wnet with an MSD TFI coil and opened them up to .060 and advanced the base timing a little. Helped a little in the mpg department. Stock is .044 I guess the drawback in opening them up more is that the plug won't last as long.
Elder User
Joined: Nov 2003
Posts: 630
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From: Stanly County N.C.
Many factors come into play while trying to determine the gap. MSD says around 50-60 or so if I remember correctly . The advantage to opening the gap is as the electrodes get further apart the spark jumps a bigger gap which has a better chance of igniting the a/f mix (larger area of spark exposed to the a/f mix). Add the higher spark voltage and multiple spark and the chances of a misfire are greatly reduced while promoting more complete burn. It takes a little trial and error to get it perfect, I open the gaps till I notice a slight miss then go down from there 005-008. This will give you whats works best in your application. I have run MSD on all my trucks 78, 2 79's, 87 and 91 MPG usually increased 1-2 mpg and the idle was much improved on the earlier trucks and starting was faster but thats about it.
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