spark plug ?

[mclendon]

350 flat top , world product sportsman II heads ,112 fuel , what plug should I use ? ... any advise would be helpful . thanks

[dereksehi]

Depends on compression 12:1 and higher I like ar12 or under I like to use ar13 I know there are a lot of guys using ar133 and ar134 but they do not have an extended tip like the 12 and 13

[mclendon]

which would be better for these heads , with the extended tip or without ? ... thanks for the advise .

[perfconn]

Use extended tip NGK with flattops

[mclendon]

thanks perfconn , which plug number should I start out with .

[perfconn]

Ngk 5673-8

[dave41]

you only get one spark to the sharpest edge. don't believe v or u double spark bull s31t

[merc123]

Ngk 5673-8

This the right one?

http://www.amazon.com/gp/product/B0006HPICW/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0006HPICW&linkCode=as2&tag=lawsraci-20&linkId=GUM7JXSVWFJTWMYP

[perfconn]

That website is misleading Although it says 5673-8 that picture is actually of a 5671A-8 which is for a 3/4 reach aluminum head.You need the tapered seat. 460 reach for the steel head.

[72Dubya]

The NGK V gap plugs definitely throw more spark. I used to run Autolite until I had a lot of trouble with my plugs loading up at idle from the jetting I had to run with my fuel, switched to the NGK V gap "equivalent" to the AL I used to run and have not had an issue since. You can see the difference if you put them side by side and crank the engine over.

[DaveBauerSS6]

I tested all the plugs when I managed a super shops in the 90s we had a ignition machine.

LMAO Stood across the counter and listened to a lot of bad information. The good old days. I miss them. LMOA some more.

[merc123]

The NGK V gap plugs definitely throw more spark. I used to run Autolite until I had a lot of trouble with my plugs loading up at idle from the jetting I had to run with my fuel, switched to the NGK V gap "equivalent" and have not had an issue since. You can see the difference if you put them side by side and crank the engine over.

Same here. Autolites keep fouling after only 2 races. I run regular NGK plugs and haven't had any issues since. I can run all season on a set and never misfire.

[dave41]

stock car racer

so you tried it under 225 ft lbs. of pressure . makes a difference

[mod71m]

The 5673-8 that perfconn recommended will work great but they are not a projected tip. The projected tip number is 5674-8.

http://www.ngksparkplugs.com/docs/RacingSpecs2013.pdf

From dyno and flow bench experience I will say that typically there is not a lot of difference between the projected vs standard plug. On the flow bench the standard plug is always a few CFM better.

From race track experience when running leaded race gas the NGK -8 will have a tenancy to fuel foul on you once in a while, especially if you are a little on the rich side. This is due to the lead in the fuel coating the spark plug and creating a conductive coating on the porcelain of the plug. Any more most of the time I run -7's with leaded race gas. They sure last longer if you're on a budget and not concerned with a few HP loss from running plugs that are more than 4 nights old.

[DaveBauerSS6]

so you tried it under 225 ft lbs. of pressure . makes a difference

Got to find a book, but I remember amperage is for jumping the gap (pressure resistance) and voltage is the spark size.
I learned it the tough way on supercharged motors.