The Ford Barn

48fordnut · 04-12-2019, 06:10 PM

I have a 276 c/I flat head 3 carbs, mild cam, petronix ignition ,and edelbrock heads. What would be a good plug to start with?

Thanks,

jim

old Tom · 04-12-2019, 06:14 PM

We used to use Autolite AL7X in our FH dragster. They worked the best.

Lanny · 04-12-2019, 08:34 PM

The plug heat range is fairly important, but also, the length of the plugs is Very
important, depending on the piston dome, and if the heads have been milled.

.

Tinker · 04-12-2019, 08:53 PM

A lot of guys like ngk's. Length and heat as Lanny mentioned, makes a difference. Every flathead is surprising different.

I use autolite 386s. 18mm and removal post ends for rajah ends. Not what you need...

They bash champion plugs. the H10s are a very nice plug. short for your application.

https://www.jalopyjournal.com/forum/...-plugs.836595/

drolston · 04-12-2019, 09:37 PM

My flathead is same as yours, except 284 inches and Offy heads. I settled on the Champion L82C. It has 1/2" thread reach for the thicker aluminum plug hole, versus 7/16" reach for stock heads. The added reach still leaves the tip of the electrode partially within the plug hole. It is a little hotter heat range.

I have a couple thousand miles and no problems with starting hot or cold, or with pinging. The plug color is a dusty grey, which is different than the light brown I found in a good running flathead, back in the day. I believe modern fuels make reading plug color less telling than in the past, so I will go with the fact that the engine runs great on the L82C Champion plugs.

Flathead Fever · 04-13-2019, 12:21 AM

Sponsored Links (Register now to hide all advertisements)

On the Champion H10 plugs I believe it is the H10C that has the longer reach. I remember a magazine article where they used the H10 plug but it was so short they had to grind the dome away to un-shroud the plug. I was thinking why didn't they just use the longer H10C?

flatheadmurre · 04-13-2019, 12:33 AM

Isn´t the C at the end just "copper plus" or what they call it...
J-10 has the real long tip.

BUBBAS IGNITION · 04-13-2019, 05:04 AM

We have always used the Champion H10C C is for copper.....

flatford8 · 04-13-2019, 05:11 AM

I’ve been using Autolite 216 in a stock 8BA and had two where the contact pulled right out of the plug..... Mark

V8 Bob · 04-13-2019, 07:12 AM

NGK 6BL or slightly hotter 4BL.

36rgtop · 04-13-2019, 08:43 AM

Quote:

Originally Posted by Flathead Fever

I was thinking why didn't they just use the longer H10C?

Longer H10C ? Really??

04-12-2019, 06:10 PM	#1
48fordnut Senior Member Join Date: Sep 2010 Location: warner robins ga 31088 Posts: 494	What spark plug to use? I have a 276 c/I flat head 3 carbs, mild cam, petronix ignition ,and edelbrock heads. What would be a good plug to start with? Thanks, jim

04-12-2019, 06:14 PM	#2
old Tom Senior Member Join Date: May 2010 Posts: 195	Re: What spark plug to use? We used to use Autolite AL7X in our FH dragster. They worked the best.

04-12-2019, 08:34 PM	#3
Lanny Senior Member Join Date: May 2010 Location: Mn Posts: 2,411	Re: What spark plug to use? The plug heat range is fairly important, but also, the length of the plugs is Very important, depending on the piston dome, and if the heads have been milled. . __________________ If mama ain't happy, ain't nobody happy. But if daddy ain't happy...RUN

04-12-2019, 08:53 PM	#4
Tinker Senior Member Join Date: May 2010 Location: MN Posts: 7,053	Re: What spark plug to use? A lot of guys like ngk's. Length and heat as Lanny mentioned, makes a difference. Every flathead is surprising different. I use autolite 386s. 18mm and removal post ends for rajah ends. Not what you need... They bash champion plugs. the H10s are a very nice plug. short for your application. https://www.jalopyjournal.com/forum/...-plugs.836595/ Last edited by Tinker; 04-14-2019 at 12:18 AM. Reason: number change

04-12-2019, 09:37 PM	#5
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: What spark plug to use? My flathead is same as yours, except 284 inches and Offy heads. I settled on the Champion L82C. It has 1/2" thread reach for the thicker aluminum plug hole, versus 7/16" reach for stock heads. The added reach still leaves the tip of the electrode partially within the plug hole. It is a little hotter heat range. I have a couple thousand miles and no problems with starting hot or cold, or with pinging. The plug color is a dusty grey, which is different than the light brown I found in a good running flathead, back in the day. I believe modern fuels make reading plug color less telling than in the past, so I will go with the fact that the engine runs great on the L82C Champion plugs.

04-13-2019, 12:21 AM	#6
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,095	Re: What spark plug to use? Sponsored Links (Register now to hide all advertisements) On the Champion H10 plugs I believe it is the H10C that has the longer reach. I remember a magazine article where they used the H10 plug but it was so short they had to grind the dome away to un-shroud the plug. I was thinking why didn't they just use the longer H10C?

04-13-2019, 12:33 AM	#7
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: What spark plug to use? Isn´t the C at the end just "copper plus" or what they call it... J-10 has the real long tip.

04-13-2019, 05:04 AM	#8
BUBBAS IGNITION Senior Member Join Date: May 2010 Location: SPEEDWAY INDIANA Posts: 4,148	Re: What spark plug to use? We have always used the Champion H10C C is for copper..... __________________ If it Makes Spark, we do it !!!! www.bubbasignition.com [email protected]

04-13-2019, 05:11 AM	#9
flatford8 Senior Member Join Date: Jan 2012 Location: Lyman,ME. Posts: 2,627	Re: What spark plug to use? I’ve been using Autolite 216 in a stock 8BA and had two where the contact pulled right out of the plug..... Mark __________________ I'm thinkin' about crankin' My ragged ol' truck up and haulin' myself into town. Billy Joe Shaver

04-13-2019, 07:12 AM	#10
V8 Bob Senior Member Join Date: May 2010 Location: Granger (Northern) Indiana Posts: 1,520	Re: What spark plug to use? NGK 6BL or slightly hotter 4BL.