droptopron

What is the thinking on this? Don't want anything fancy because I don't buy into the benefit.
'70 442 455 that has an GM style HEI. Not sure if its stock or aftermarket.
Do I run an AC R43S or or an R46 and with what gap?
TIA

oldcutlass

What have you been running? It calls for R45s or an R46S. With an HEI, I like a .045 gap.

lemoldsnut

R45S at the .045 gap. works great

Fun71

I use the same plugs from when the car had points just with the gap opened up slightly.

droptopron

I'm not suere, Whatever is in there was there when i bought it, I'm pulling one this weekend to see what shape its in.

droldsmorland

Get a set of good Ole autolites. They work great with HEI. Set at .040. Optomize your timing curve and adjust the A/F mix screws with engine warm and choke off 6-750 rpm idle. You can also use the vacuum gauge to adjust timing. Your looking for the highest vac reading. And as much timing as the engine will tolerate with your fuel, elevation above sea level and driving habits.
A good starting point is 10-12* of base timing, 8-12* more at idle from the advance canister (get an adjustable travel not rate can) running off straight manifold vacuum, then the rest all in for a total of about 38-40* at 2700-3000 rpms. I too had good reading plugs with sooty tails...once I super tunned as per above all is good. I had a popping out of the exhaust at idle. The vac can was bringing in too much timing at idle.

RetroRanger

I think the r43 is the recccomended 70 points 455 plug. I just got some of those and plan to run them w HEI and 040 gap as soon as I get running in the next few weeks.