Actually, .030is fine, maybe, .035. Just be aware, when the gap is increased, it can increase the tendency for the voltage to seek a lesser path of resistance. If your wires are in good condition, you should be fine with 30/35

 

 

Pertronix Flame Thrower II coil and distributor

With electronic ignition you should be able to go .040-.045".

 

I'm going off an a tangent I know, but my nephew tells me he changes plugs on his race / street car about every 500kms.
Last weekend I changed plugs on my boy's 4.6L in a 2003 F150. They were in there 103K kms (64,000 miles) with only slight wear and overall min differance in gap from new ones. I dont recall that kind of life in my old 289 or even the 351 plugs
Sounds like you've got a good handle on your ignition system. Me, I'm still trying to decide what im gonna stick in my 302 when I get to firing it up.
Safe travels!

 

This is on an engine with fuel injection, timing control, and high voltage spark.

 

The P-II is high-energy (much more power than the original Ignitor or points), so the gap can be adjusted for the expected use. More gap will raise discharge voltage, exposing more mixture to ignition. Or less gap will use the increased energy for longer spark burn. Extreme conditions such as high-compression dictate different gaps.

Most use a balance between the two using high-energy (HE), such as GM with .050" to .060", or Ford TFI setting theirs at .044". Newer distributorless Fords at .049-.053". Racers often increase gap until it misses, then back-off .005". The voltage is still lower than CDI, and few seem to freak about that. 🤷‍♂️ Me? For street use, I gap HE at .045" to .050". Do your thing.

 

.032". Over the span of use and electrode degradation the gap will widen.

 

Ok, back to your problem.
You don't specify what year is your motor or heads so it's kind of a crap shoot for us offering you suggestions (you have gotten a lot of really good ones).
Is it an early 302, or a later with roller cam ?
I know that Ford suggests my 302 (1989 ?) be between .048 and .052. It has a TFI distributor utilizing a wide cap (narrower early caps are at risk of crossfire with high energy coils and poor plug selection/ gap or condition).
I would try to find out approx what year is your motor and or heads are and then look up ford specs for plug gap.
Then gap no more than an additional .007" as per Pertronix recommendation. I would try one plug thats easy to access and test there. Once kinda confident what you have done is ok do the other 7.
I would also look at what OEM plug is available (rock auto is a great source for cross info) and choose a good one. Seen once too often where someone puts in an after market "hot" or trendy plug only to chase intermittent ignition problems especially on "coil on plug" setups.
Good luck !

 

As with all things, there are many confusing 'facts' that may be misinterpreted. Here's one for you from the GM Motorhome section. While gap is relatively unimportant for easy-to-light mixtures such as power AFRs (this is where the "gap doesn't matter", is because it is on WOT dyno only and at low AFR); wider gaps are more effective for lighting sparse cruise mixes for economy - important for street or endurance racing.

So while you might look at this chart and make some assumptions about gaps, the driving factor behind the gap differences is the plug construction. Standard vs exotic metals. What you see here are requirements to support advertised spark plug life. In order to increase plug life, the gap is reduced to also reduce wear. Bingo, amazing plug life for your motorhome from those expensive plugs.

So, while the info could be used manipulated to support other BS, the bottom-line is that gaps are often specified for completely different reasons, and sometimes as silly as WOT-only or maintaining the advertised plug life, rather than what actually works better for your use. WOT performance all the time is not needed by most here, nor is 100k plug life. Use what works for your use, and gapped to perform how you need it.