I know I should be running colder plugs with running all the bolt-ons and upgraded twins. Most guys are running atleast 10.5-11.5 race plugs - think I could do better than 370 rwhp at 15 psi with colder plugs?

 

9's are fine. i know a car that made 500+rwhp with 9's... my FD still has stock plugs in it 7's and 9's ! lol

 

if you are not getting any break-up new the 10.5s won't do much at all. if you ignition is good with no detonation you are fine. teh differnce it makes is not eh heat range for power but the electrode type of the racing plug.

 

If anyone one figures out a way to not burn up the plugs, please let me know! Rotaries eat plugs, but I know that isn't really your question.

Some cars seem to be fine on the stock plugs or all 9s, but others do better with colder plugs. I dynod my car with all 9s and the curve was shaky at the top end. I have seen it suggested that colder plugs can smooth the curve, so I installed some B10EGVs (which require a special socket to install -- search for details) in hopes of both reducing some misfires I was experiencing and smoothing out the curve. I haven't been back to the dyno, but the misfires are gone. There have been some good threads on this lately - search for "B10EGV" and see what it turns up.

-Max