Ok, say you've just hot rodded your big honkin 390. New cam, pistons, intake, carb... the works. Now you need to gap your spark plugs -but with all of the mods, what do you do? Set them to stock or is there a formula to account for performance enhancements? What I've read indicates using a cooler plug and tighter gap for higher compression but as to how cool and how tight is left up to the individual via best guess. I can't help but think that there's a better way... Thoughts?



spots

 

.035 if the brain still works.. kind of depends on your setup too though.(HO ignition?)

 

I think with electronic ignition, one can get away with a larger gap--like up to .050 or more. The tech-line of the distributor manufacturer--if you changed to one--might be helpful.

 

Crane Electronic conversion but everything else is stock.


Should a compression increase (9.5) be taken into consideration?

 

The gap that you can run is really decided by the ignition system you have. As a general rule, you're .035 for a stock points/coil system. If you're got an electronic ignition then usually you've got a hotter coil and should gap the spark plugs wider. The are several crane conversions. If you've got the xri and you're running a stock coil then .035.

Good Luck

Tracy

 

Use a smaller gap when running a stock ignition coil & module with a high compression motor, .035"-.040".

However, if you go to a performance igntion system which is strong enough, you can open up your gaps wider, which burns your fuel more completely-usually .050" to .055".

If you decide to get a new distributor, consider our custom curved Duraspark Distributor built with our new Full Length Oil Impregnated Bronze Bushing. The full length bushing improves timing stability and spark scatter. If stock appearance is not an issue, take a look at our one piece D.U.I. Distributor. Whether you choose the Duraspark or the D.U.I., we curve each on a distributor machine based on your engine combination. Please see them at:

http://www.performancedistributors.c...stributors.htm</O

Also, there is now an excellent installation article on the D.U.I. Distributor on the Ford-Trucks.com site at:


https://www.ford-trucks.com/article/idx/0/358/article/DUI_Ignition_Installation_In_A_Ford_351W_V8.html


Speaking of wider plug gaps, we have recently developed the 18 Volt Mini-V.I.P.-(Voltage Intensive Power) step-up regulator that can be ran with our D.U.I. Distributor. It allows you to run a .070" plug gap! Of course, with this kind of spark, you can run a richer fuel mixture, making more power.

http://www.performancedistributors.com/new.htm