what have you guys found to be the best plug heat range and timing on the indy headed 408's? currently using ar3934 with 10.75 comp and reading the plug it looks like it wants more timing. the heads are the 360-1's.

hi dave ,guy over here made 640 with the -1 408 and 36 was best on dyno and ngk -7 .i run the -7 and trying 40 deg timming ,potting - 10 and 150 gas on sunday see how it goes.

thanks Ian, but what do you meen by potting 10 and 150?

Hey Dave , wheres the timing @ now?

timing is at 35*, but the ground strap on the plug shows color difference nere the tip only.

Give it what it needs, bump it up a couple at a time

thanks Ian. i advanced the timing to 37* from the previous 35*. my advance is locked out and i notice when i rev the engine with a light on it, the timing will drop back 1*. so, i have 37* at idle and 36* at 3000 and up. anyone ever notice this with lockedout timing?

Mine moves a little, its the play in the slot between the dist and drive gear

ok, but how many degrees does your fall back? when i had a msd digital6 it would fall back 2*. this only happens when timing is locked out. i'm now using a summit box which i believe is made by mallory. i like it way better.

I run a 6al with locked 34* @ 1200 idle, mine moves 1 or 2 degrees to 2k then seems to smooth out at high rpm