Which Spark Plug
 

Hey guys, I am needing some advice on selecting a spark plug. I have a 421 SBC on alcohol. The compression is 14:1 I have a MSD 7AL-2 with a baster coil to provide the spark. Not too familiar with alcohol. What plugs would yall recommend. Any help or advice would be greatly appreciated.

Chris

Which heads? If you have Brodix heads you can go to their website and they have recomendations. I run the NGK plugs which they call for with Track 1's



Zip.

They are Pro Comp aluminum heads. Don't know that much about them. 190cc intake runners
2.02 intake 1.60 exhaust SS valves
Also what gap should I start at?

Chris

I run .030 gap with alcohol.

Zip.

Appreicate the help, which NGK plug?

Chris

NGK-R5671A-9 for alcohol

NGK-R5671A-8 for gas

Depending on the compression you have you should probably index the plugs just to be on the safe side.

Zip.

Thanks Zip

when you index them.witch way sould they be facing ?????

My Enderle Alcohol injected Altered has a 13.5:1 sbc 434 with Brodix 11X heads and I run NGK B9ES plugs gaped at .035 and I run an MSD7AL3 with a Pro Power coil. Very reliable with no issues.

between 10 and 2

Autolite 3910's

Thanks guys. I appreciate all the help. When indexing the plug, the strap should be pointed down correct.

Chris

Correct.

Zip.

plugs
 

i say stay away from champion plugs , bosch arent worth a $hit either i haven't had them last in anything bikes cars, (lawn mowers) ect..
ngk are great plugs, autolite - definitely ac delco

sorry still just a little confussed.with the head off.the gap should be facing the valves or the piston.. :oops:

I index them due to the high dome pistons and i don't want the piston to close the gap up. As you know most high dome pistons have a radius cut in the dome to clear the plug ends, but there is some power gains that can be associated with indexing. i don't know how much but all agree there is some. Indexing also allows for better flame travel, but to answer your question i think the open end should be facing the valves, but not everyone thinks this way. Here is a pretty good article by Autozone, which by the way sells the indexing washers, so does jegs,summit,etc.

JMO

Zip.

http://www.advanceautoparts.com/engl...#Power%20Gains

Bigray, I think it is facing the valve, but double check me on that... it has been awhile.

Am I the only person out there that has fouled Autolite, NGK, Champion, etc... THEN WENT to Bosch "Platnum" & never had a problem since??? When jetting or tuning a carb (such as new one) I will never run anything else... they simply don't foul. I had NGK, & crossed over the correct heat range for my BBC & never had a problem again... they cost more, but who cares. JMO

I draw a black line (permanent marker) on the porcelin where the backstrap is on the plug so i can see where my mark is..i try to get the backstrap in the 12 o'clock position..but 10 and 2 will work...i index for clearance insurance only..keeping backstrap as far away from piston as possible.

Brian

Thanks Guys,
Brian I think you told me that when I was up there last time. Man I can forget things. I guess we are all getting old. :D

Chris

I run NGK B9ES plugs gaped at .035 and I run an MSD7AL3 with a Pro Power coil. Very reliable with no issues.