[78w72]

looking for suggestions on the best plug gap for my 467 E-head stroker & for the average lower power street engine thats maybe 100-150hp above stock.

ive read most people use ~.045 that was a reduced gap size from GMs original ~.060 for hei's & ive been using that for 20+ years with no noticeable issues, but then i read this from NGK that talks about reducing the gap .004 for every 50hp above stock, which is kinda confusing considering the range of hp increases on pontiacs today... if an engine is say 250hp over stock they want you to reduce the gap .020?? never really heard of .025-.030 gap sizes on hei engines.

Reference: From NGK's FAQ: Spark Plug Gap -
"Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005"."


heres some general specs of the 467.
RPM round port 72cc heads. 10.7 comp.
NGK plugs
original OF cam, 1.5 HS rockers.
SD ported HO intake & cliff built Q-jet.
sun tuned prepped HEI with accel in cap super coil & "MSD HEAT" in cap module but also have run the stock GM module & will again if/when the MSD dies.
i use 91 straight fuel but occasionally will use 93 10% ethanol.
let me know if any other details are needed.

im mainly looking for what most guys with similar ~500hp combos are using for gap size with HEIs as well as mild street engines in the 350hp range using a stock AC delco r45 type plug.