Im sure this has been talked about numerous times about what plug to use for vortec heads but what gap is best I don't think so.

My car is a 350 tbi with an lt1 cam and 906 heads that were cut down slightly. I had NGK tr55s in them gapped at .035 and it ran well, but my compression is 9.8:1 so I thought a colder plug would be better and I found a set of r43lts and gapped them at .040 as I have a 8226 blaster coil and a thought it would be ok. But it misses now and power is awful. I'm going back to the Ngks, but I'm curious as to anyone else's trial and error on the correct plug heat range and gap.

Thanks all.

 

r42lts @ .035“ works pretty well in my 10:1 vortec headed 355. My knock counts went down significantly when switching from a r44 plug to the r42.