Originally Posted by Tommy B
Thats the plug heads orignally took . I heard to use delco r43xls now . Do i need to go up or down in heat range since i'am 30 over now and added a bigger cam and about .5 point compression , gears and a convertor . I don't drive the car on the street , its just a toy at the track . I tried NGK bpr4es but the plugs stay very white and i get a pop now and then at idle ,more so when engine is not to operating temp . ( I think that means the plug is too hot correct ? ) i have msd ing and 6al box if that matters . I gapped the plugs at .35 also .
It looks like you have problems other than just spark plug heat range.
You went bigger on the camshaft, and just a touch on compression. You will need to re-jet the carb richer, by a couple jet sizes, at least. The "very white plugs" says you are running too lean now. The "pop now and then at idle", says you might have a real lean mixture at idle.(possible vacuum leak) Also MSD recommends a plug gap starting at .050 to no more than .060, for their products to operate best. The fuel you are using will play a part in your tune.
A spark plugs "heat range" is determined by the engines cylinder temperature. In other words, a "hotter plug" is designed to perform best in higher temperature's, as in a "lean mixture". and "colder plug" would perform better with a richer mixture. The plug does not "burn" hotter, it will just dissipate the heat slower, keeping the plug "hotter".
You also changed gears, and converter which is going to have to be close, rpm wise, to the "grind" of the camshaft.