why a non-projected tip? does it have flat top pistons? a 7 may be a little cool but I think it's too rich/poor burn-tune-up.
Yes it is flat top pistons, i just wanted to try them out but the idle was smoother with projected tip
the only reason I can think of to not use a projected tip is if you have a very intrusive dome on the piston. I use autolite 3926's and they seem to burn well for driving. an ngk 6 is close to the 3926 and ngk 5's are pretty hot. i'm not an autolite or ngk fan specifically so either can be made to work. i'd try cleaning up the a/f ratio first and make sure the timing is proper. that engine should make a lot of vacuum with that small cam and big cubes. high vacuum engines don't necessarily need more jet area. big 4bbl carbs don't always mix good at low rpm but that may not be an issue here. I don't see oil use but it looks like carbon crude from a poor burn. this modern gas can get gummy and cruddy.
Thank you for your answer! I will try to put in ngk 6 projected tip and try to lean the carb a bit, i have a msd pro billet distributor now with the 6al system but im going to switch to a FBO distributor(Mopar original) with vacuum advance, i think thats better for the street. I have about 17 hg/inch vacuum at idle now but i believe that can be higher with a vacuum advanced distributor. FBO blueprinted one for me, 16 initial and full manifold vacuum that bring the timing to 30 at idle, mechanical full advance at 3200 rpm and 34 degrees.
