I found a thread that gave this information

heat range for the L series engine (not full race) cool BPR7ES, warm BPR6ES, hot BPR5ES, the variables are condition and usage

What I need to know is I have a stock L24 with an E31 head. I have blow-by on cyl 5, and my compression is as follows from cyl 1 to 6: 120, 120, 120, 120, 40, 120. My rear carb will not tune quite right, it runs rich all the time (probably needs rebuilt) but the front carb is in good tune. I just need a 'short term' solution here since I'll be replacing the engine this year (I hope). What plug would be best for my car? The plugs always seem to foul so I will end up replacing them on a regular basis after doing some driving then letting it sit for a while, or doing a lot of driving. So really expensive plugs, like $8/each, are a bad choice unless they will not foul (yeah, right).

Any help on this would be great!! Thanx guys & gals!! :classic:

Could you guys also tell us what the difference is between a cooler or hotter plug and what applications they have.

use the plugs you have been using and buy an extension foul preventer for the bad cylinder's plug. they should have those at your parts store. i've been told they work pretty well.