The Ford Barn

Ed Pitts · 02-26-2018, 02:22 PM

What are the advantages/disadvantages of using a 0.035 plug gap vs. a 0.025 gap originally recommended for the 59 engines. I have a 12 volt system with the Bosch blue coil. Ed

BUBBAS IGNITION · 02-26-2018, 04:25 PM

No advantage unless compression is changed a bunch. Plug gap goes with engine compression and air fuel ratio...
Bosch blue might make the ignition more efficient but the engine will take whatever it needs for spark.
Ex: A 20,000 volt coil on a flathead might at idle use 5000 volts , the other 15,000 is reserve voltage for hills, lean air fuel ration and normal wear.

JWL · 02-27-2018, 07:18 AM

If you read my book you will find that I tested differing plug gaps. My tests on an 8BA engine did not show any significant value in altering gaps. One thing to keep in mind is that wider gaps require more voltage and can lead to cap and wire misfire/crossfire problems and failures.

Dr. Jacobs explained, in his book, Performance Ignition Systems, the ideal plug gap is .100. We would probably need to use a "J" series sparkplug to utilize such a gap in our Flatheads. Too, there might be ultra lean A/F economy conditions which can benefit from such a huge gap but most "normal" conditions would not. But perfect cap and wire components would be essential for using a gap so wide.

JSeery · 02-27-2018, 09:12 AM

For anyone new who doesn't know about JWLs book.

john in illinois · 02-27-2018, 01:47 PM

You can buy a copy here.

http://www.vanpeltsalesstore.com/L-1...son_p_511.html

I bought mine direct from JWL and you could probably PM him to order one.

John

Pete F · 02-27-2018, 02:24 PM

Sponsored Links (Register now to hide all advertisements)

If I’m tuning a stock ignition I run .025-.032 gap depending on the compression if I’m tuning a car with electronic ignition I run .035-.040 again depending on the ignition and the fuel system.
Remember it takes more spark to fire a lean mixture and depending on the setup things can change.
And my belief is to use the factory manuals as a guideline since the fuel is totally different today compared to what was around in the 30’s and 40’s
And than throw in cams , heads and exhaust and it totally changes the game.

Sent from my iPhone using Tapatalk

02-26-2018, 02:22 PM	#1
Ed Pitts Senior Member Join Date: May 2010 Location: Irving, Texas Posts: 598	Spark plug gap What are the advantages/disadvantages of using a 0.035 plug gap vs. a 0.025 gap originally recommended for the 59 engines. I have a 12 volt system with the Bosch blue coil. Ed

02-26-2018, 04:25 PM	#2
BUBBAS IGNITION Senior Member Join Date: May 2010 Location: SPEEDWAY INDIANA Posts: 4,148	Re: Spark plug gap No advantage unless compression is changed a bunch. Plug gap goes with engine compression and air fuel ratio... Bosch blue might make the ignition more efficient but the engine will take whatever it needs for spark. Ex: A 20,000 volt coil on a flathead might at idle use 5000 volts , the other 15,000 is reserve voltage for hills, lean air fuel ration and normal wear. __________________ If it Makes Spark, we do it !!!! www.bubbasignition.com [email protected]

02-27-2018, 07:18 AM	#3
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: Spark plug gap If you read my book you will find that I tested differing plug gaps. My tests on an 8BA engine did not show any significant value in altering gaps. One thing to keep in mind is that wider gaps require more voltage and can lead to cap and wire misfire/crossfire problems and failures. Dr. Jacobs explained, in his book, Performance Ignition Systems, the ideal plug gap is .100. We would probably need to use a "J" series sparkplug to utilize such a gap in our Flatheads. Too, there might be ultra lean A/F economy conditions which can benefit from such a huge gap but most "normal" conditions would not. But perfect cap and wire components would be essential for using a gap so wide.

02-27-2018, 01:47 PM	#5
john in illinois Senior Member Join Date: May 2010 Location: Illinois Posts: 2,184	Re: Spark plug gap You can buy a copy here. http://www.vanpeltsalesstore.com/L-1...son_p_511.html I bought mine direct from JWL and you could probably PM him to order one. John

02-27-2018, 02:24 PM	#6
Pete F Senior Member Join Date: Feb 2017 Location: Bloomfield,ny Posts: 130	Re: Spark plug gap Sponsored Links (Register now to hide all advertisements) If I’m tuning a stock ignition I run .025-.032 gap depending on the compression if I’m tuning a car with electronic ignition I run .035-.040 again depending on the ignition and the fuel system. Remember it takes more spark to fire a lean mixture and depending on the setup things can change. And my belief is to use the factory manuals as a guideline since the fuel is totally different today compared to what was around in the 30’s and 40’s And than throw in cams , heads and exhaust and it totally changes the game. Sent from my iPhone using Tapatalk