The Ford Barn

allen · 03-01-2011, 12:54 PM

Hi guys switch to a mallory electronic distributor in there instructions they said to play with the gap on the plugs, running a/c think there 44, its on a 255 with dual 97s 3/4 cam, set now at 35 anyone out there found a better gap, Runs ok now just don't know if i am leaving anything on the table, thanks AL

rotorwrench · 03-01-2011, 02:33 PM

High energy electronic types usually run a wider plug gap. The ignition unit manufacturer's instructions should be good for any brand of plug for your motor.

wiretwister · 03-01-2011, 11:43 PM

It was easier back when we used a thin dime.

IF LIFE GIVE YOU A SNOW STORM -- MAKE SNOW ICE CREAM MMMMM GOOD

allen · 03-02-2011, 09:52 AM

Quote:

Originally Posted by rotorwrench

High energy electronic types usually run a wider plug gap. The ignition unit manufacturer's instructions should be good for any brand of plug for your motor.

Thanks rotorwench , I read the instructions and they said play with the gap ??????, Think i will try open them up as you said maybe to 40 and see whats up, Who knows might even have to install seat belts if it open up more thanks al

BUBBAS IGNITION · 03-02-2011, 11:23 AM

Plug gaps go with combustion chamber design and air fuel mixtures.
The wider gaps were part of a emission package and very lean air fuel mixtures.
The high energy ignitions were developed due to the "no tune up required" regulations with certified emission for 50,000 miles . ( today its 100,000 miles)
A old engine ( lets say flathead ) doesnt show any need for wider gaps as most ( especially modified cams and dual carbs), all you gain is higher coil output and overheated parts . Short life etc on ignition components......

There may be some changes in performance from time to time with plug gap changes , however if so its because you fixed a problem in another system etc...

Heres a scenario i like to use .

Scope hooked to stock good running flathead running at idle shows a actual need of 5,000 volts per plug at idle. Proper air fuel mixture of 13-1 per the day of manufacture. .030 plug gap .Plugs are taking approx 2,000 to jump the gap and ignite the hydrocarbons of fuel. The other 3,000 is used up with rotor gap and resistance in the sytem etc.

Now lets add two carbs making the air fuel mixture richer (lets say 12-1) Scope now shows 4,000 volts as richer air fuel mixtures take less . More fuel hydrocarbons are easier to ignite requiring less output from the ignition.

Now lets widen the gap to the plugs to .045. The engine will now use 6,000 volts to fire the longer duration spark based on the wider gap and the jump off the plug point on the scope will show it now requires 3,000 volts to jump the plug etc.

And the story goes on and on. A compression increase ( milled heads) will cause a increase in spark out put.
So lets say you mill the heads (increased output needed) and added twin carbs ( lower output needed) then we would be back at the orginal specifications..

Makes it all clearer right ??????

Ol' Ron · 03-02-2011, 12:48 PM

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Jim I think 15:1 is a bit lean.

BUBBAS IGNITION · 03-02-2011, 04:51 PM

Quote:

Originally Posted by Ol' Ron

Jim I think 15:1 is a bit lean.

Thanks Ron i fixed that part for sure......yep 15-1 would be a bit on the lean side......
You doing ok now days.???

Ol' Ron · 03-02-2011, 07:08 PM

I'm getting there, I was out in my shop for a while yesterday, but didn't last long. I guess it'll take a while longer. Thanks Ol' Ron

345 DeSoto · 03-03-2011, 06:54 AM

Jim,
THANKS for the explanation of the spark gap requirements. It answered a question in my mind that's been bugging me for years. So, all things being equal, one should just go with the gap the book for the particular engine calls for. Never DID know why the huge gap in the HEI ignition systems...now I know...

BUBBAS IGNITION · 03-03-2011, 10:31 AM

Quote:

Originally Posted by 345 DeSoto

Jim,
THANKS for the explanation of the spark gap requirements. It answered a question in my mind that's been bugging me for years. So, all things being equal, one should just go with the gap the book for the particular engine calls for. Never DID know why the huge gap in the HEI ignition systems...now I know...

I just happened to be in the middle of this clean air act when it happened. Manufactures were required to meet emission requirements for 50,000 mile ( stage one) and the old contact systems couldnt do this without some needed maintance etc. Voltage levels were increased as well. A few years into the program they actually started dialing back the voltage as it was really hard on parts like cap rotor and wires.
Today is another standard. my 2004 GMC has 86,000 on the factory plugs. I looked at them during the last oil change and they are perfect.

03-01-2011, 12:54 PM	#1
allen Senior Member Join Date: May 2010 Location: petal mississippi Posts: 550	Plug gap Hi guys switch to a mallory electronic distributor in there instructions they said to play with the gap on the plugs, running a/c think there 44, its on a 255 with dual 97s 3/4 cam, set now at 35 anyone out there found a better gap, Runs ok now just don't know if i am leaving anything on the table, thanks AL

03-01-2011, 02:33 PM	#2
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,483	Re: Plug gap High energy electronic types usually run a wider plug gap. The ignition unit manufacturer's instructions should be good for any brand of plug for your motor.

03-01-2011, 11:43 PM	#3
wiretwister Member Join Date: Jul 2010 Location: Missouri west of St. Louis Posts: 45	Re: Plug gap It was easier back when we used a thin dime. IF LIFE GIVE YOU A SNOW STORM -- MAKE SNOW ICE CREAM MMMMM GOOD

03-02-2011, 11:23 AM	#5
BUBBAS IGNITION Senior Member Join Date: May 2010 Location: SPEEDWAY INDIANA Posts: 4,148	Re: Plug gap Plug gaps go with combustion chamber design and air fuel mixtures. The wider gaps were part of a emission package and very lean air fuel mixtures. The high energy ignitions were developed due to the "no tune up required" regulations with certified emission for 50,000 miles . ( today its 100,000 miles) A old engine ( lets say flathead ) doesnt show any need for wider gaps as most ( especially modified cams and dual carbs), all you gain is higher coil output and overheated parts . Short life etc on ignition components...... There may be some changes in performance from time to time with plug gap changes , however if so its because you fixed a problem in another system etc... Heres a scenario i like to use . Scope hooked to stock good running flathead running at idle shows a actual need of 5,000 volts per plug at idle. Proper air fuel mixture of 13-1 per the day of manufacture. .030 plug gap .Plugs are taking approx 2,000 to jump the gap and ignite the hydrocarbons of fuel. The other 3,000 is used up with rotor gap and resistance in the sytem etc. Now lets add two carbs making the air fuel mixture richer (lets say 12-1) Scope now shows 4,000 volts as richer air fuel mixtures take less . More fuel hydrocarbons are easier to ignite requiring less output from the ignition. Now lets widen the gap to the plugs to .045. The engine will now use 6,000 volts to fire the longer duration spark based on the wider gap and the jump off the plug point on the scope will show it now requires 3,000 volts to jump the plug etc. And the story goes on and on. A compression increase ( milled heads) will cause a increase in spark out put. So lets say you mill the heads (increased output needed) and added twin carbs ( lower output needed) then we would be back at the orginal specifications.. Makes it all clearer right ?????? __________________ If it Makes Spark, we do it !!!! www.bubbasignition.com [email protected] Last edited by BUBBAS IGNITION; 03-02-2011 at 04:50 PM.

03-02-2011, 12:48 PM	#6
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,889	Re: Plug gap Sponsored Links (Register now to hide all advertisements) Jim I think 15:1 is a bit lean.

03-02-2011, 07:08 PM	#8
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,889	Re: Plug gap I'm getting there, I was out in my shop for a while yesterday, but didn't last long. I guess it'll take a while longer. Thanks Ol' Ron

03-03-2011, 06:54 AM	#9
345 DeSoto Senior Member Join Date: Jun 2010 Location: Skaneateles,NY(summer)/Port St.Lucie,FL(winter Posts: 126	Re: Plug gap Jim, THANKS for the explanation of the spark gap requirements. It answered a question in my mind that's been bugging me for years. So, all things being equal, one should just go with the gap the book for the particular engine calls for. Never DID know why the huge gap in the HEI ignition systems...now I know... __________________ ..."If my calculations are correct, when this baby hits eighty-eight miles per hour... you're gonna see some serious shit"...