Its time to get the car out of summer hibernation and some fresh plugs are probably in order so wanted to get some thoughts on whether to go with what I have been running or go with something else. Currently running Autolite 23. Motor is a 10.5:1 451, OOTB Edelbrock RPM heads, I'm limited to 91 octane at the pump. Cam is a solid .520 lift @ 254, 800 Edelbrock carb, Firecore distributor, chrome box, MSD Blaster coil. The plugs look clean now and if anything maybe on the lean side.

I'd go w/a #7 NGK or it MAY like the hotter #6............

Regular 5/8 head NGK plugs @$20 set

I have used that same plug in similar motors, they worked fine
If it ain't broken why fix it In other words if they look good now use them again

Would that be an FR or XR?

I'm not opposed to using the 23s again, just curious what other options may be out there.

I'd put NGK #6987 in there. Extra projected nose, extra wide gap, super inexpensive plug. They are the OEM plug on a bunch of cars including some Jeeps. $2 each from Summit.

https://www.summitracing.com/parts/ngk-6987

I'll see if this one cross references to something close in an Accel shorty plug. I have to use the shortest possible on #8.

How does that plug compare to the AR3923 as far as heat range?

I ended up going with the NGK 6987s, the main reason is they were in stock, cheap, and you recommended them. What would you gap them at?

I don't think I've ever gapped those plugs. Just run them out of the box. I've checked the gap a few times and it is always at spec so I just leave them alone. They are a wide gap plug.......

Ok, will do. Thanks for the response.

The 6987 is a ZFR6F-11G plug. plugs are pre-gapped to 0.043"

I think the code breaks down as:
Z - extended projection
F - 14mm diameter x 1.25mm thread pitch, 19mm long threads (3/4" = 19.05mm), 16mm hex (5/8" = 15.875mm)
R - Resistor plug
6 - Heat range 6. Seems to be good for street engines. For race engines I usually use a colder 8 heat range spark plug.
F - Firing end construction, I think "F" is a code for how far the projected tip is, but I don't see it listed in the chart?
11 - Pre-set plug gap 1.1mm = 0.043" (0.433071")
G - I think this is Copper core Ground Electrode?

Thanks for the added info on those.

I wanted to see what they were. I haven't used the extended projection type plugs. I have been using the BKR6E-11 type plugs, standard projection tip, ISO 50.5mm (1.98") outer length vs JIS 53mm (2.086"). Just a slight more clearance between plug end and shock tower.