how do you know what type(heat range) of spark plug to use?
Im ready to fire up my 400 but i don't know what Plug to get for it.
the cam i'm using is the Lunati Bracket Master 2 in summit it's specs are:230 degree/230 degree duration@.050",.480"/.480" lift
I'm also running a Weiand single plan intake a Holley 650 DP i will be running pump gas factory ignition (for now). any help will be great. Thanks in advance....


Tommy

 

It's almost trial and error since so many things can affect the plug temperature. What works good in one engine might not be best for another. Try a cold plug like R43TS. If it fouls up too much then go hotter with R44TS. The plug temperature range is the actual temperature of the plug. The goal is to have the tip of the plug between 450* and 850*.

Go to the Calgary Drag Racing Association web page. Click on Tech Tips then click on Spark Plugs.

 

it's a lot like guessing. actually i start with a couple of steps colder than factory and see how it does. there is some good info here on plugs that may help you.

http://www.calgarydragracing.ab.ca/

 

i always heard min 800 degrees cold and like 1500 hot. One that does not foul during cold start and does not contribute to detonation at operating temps and normal ignition timing.

 

Like Stephen suggested, a 43 is usually a good place to start. The number he gave you is for tapered-seat plug holes in the heads; make sure what kind of holes your heads have, and get the right seat type to go with it. Post what heads you have, maybe someone can tell what plug type to use, then you have to do the experimenting with heat ranges.

 

http://www.acdelco.com/html/pi_plugs_ident.htm

I always recommend the extended tip plugs. It gets the tip just a little bit farther into the combustion chamber to ignite the air/fuel.

 

A good article on "reading" plugs.
http://www.nightrider.com/biketech/readplugs.htm

 

The guys pretty much covered it. If you start with too hot a plug you risk engine damage from preignition. Start cold and if they foul, move to a hotter plug til you get a light tan color on the insulator. Tapered/motor seat plugs are usually found in cast iron heads and gasket seat plugs are in aluminum.