What gap to run?

HwyStar

HwyStar

Registered User
I just ordered the last of what I need to get the car together. So, it will be running again in the next week or two!! My last question is, what gap to run on the plugs? I had problems when I was spraying the Mark 8 with 'blowing the spark out.' I solved that by going to low resistance plug wires and gapping the plugs down to.030". That was with a 125hp shot. If I have a MPx w/coated rotors running at 15% od, is it really that important on these cars? I have always seen low voltages with these cars which made me not worry about the gap. But, again I have never seen one of these cars pushed this hard in person.
 
Man thats tight. Were you blowing it out at .035? How much power are you making? Does your car have a long start time?
 
In addition to cylinder pressure the type of plug you run also plays a large factor. Some plugs require less energy to create the flame kernel. That said the idea being running a good performance plug is so that you can run a larger gap. I use the autolite xp103 plugs and I run those at .035. The autolite AR103 would allow for a greater gap but they don't have the longevity that the xp103 plugs have.
 
I got a set of Autolite Irridium plugs. Ive noticed lower voltages on other cars too with Irridium plugs. Anyone notice long crank time?
 
90sc35thann said:
In addition to cylinder pressure the type of plug you run also plays a large factor. Some plugs require less energy to create the flame kernel. That said the idea being running a good performance plug is so that you can run a larger gap. I use the autolite xp103 plugs and I run those at .035. The autolite AR103 would allow for a greater gap but they don't have the longevity that the xp103 plugs have.
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I've been using the same xp103 plugs in my 91 SC for several years.

David
 
I got Autolite XP5144's, the irridium plugs. Good, or bad idea? I noticed you guys have mentioned xp103 and xp104s more than once. Do I need to change heat ranges?
 
The last number is the heat range. I would use one that ends in a 3. The lower the number the colder the plug.
 
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