325trooper

iTrader: (2)

Exactly how do different heat ranges of plugs affect performance and how do you go about choosing the best for an application? For instance, NGK has the TR6 (one heat range colder than stock), R5724-8 (3 ranges colder), and the R5724-9 (4 ranges colder). I assume the more power you make, the colder plug you want, but why? How would someone choose the best plug for an n/a 436, or a 700rwhp turbo setup, ect.

V6 Bird

iTrader: (15)

A general rule of thump for forced induction/nitrous would be to run a non-projected tip with copper.

If you have a tapered seat style head, you can run the gasket seat type plugs but be cautious when tightening the plug down.

For your case, I generally shoot for an 8 or a 9 non-prjected tip, style plug. with 3/4 reach or .708mm reach depending on the chamber and piston clearance. Something you should check during mock up really.

Some part numbers for your application would be:

R5671a-8, 9 or 10 in NGK 10 being the coldest
AR3934,3933,3932 in Autoloite Racing plugs. respective to the NGK's above them.

When tightening the plugs I generally tighten once snug another 1/4 to 1/2 to crush the gasket.

The idea is to check the threads on the plugs after a dyno pass or a pass at the track and check for color. Once you get an even color on the threads, its the right heat range. Then you check the top face of the plug for color on A/F mixture, deep down inside with a microscope for color rings, and the ground strap for timing at heat there as well. Search on google for plug reading tips and you'll get a better understanding of what you are looking for as well as tips on what to look for and how to use a plug for indexing. You can gain some power using the right plugs and setting the timing and fuel curves for that added power output nad a slightly competitive edge if you do it right.