I've got a 440 with Stealth heads. Compression is about 8.2:1 as it's a late '72 engine form an RV, but does have a forged crank. I running a Lunati roller cam with these specs:

Advertised Intake Duration: 270
Advertised Exhaust Duration: 278
Intake Duration at .050 Inch Lift: 219
Exhaust Duration at .050 Inch Lift: 227
Intake Valve Lift: 0.515
Exhaust Valve Lift: 0.530
Lobe Separation: 110
Intake Center line: 116

Running an FBO electronic ignition with one of their custom curved distributors tailored to this cam. My question is this, what heat range plugs should I be running? I use NGK and prefer to stick to these. The car is a heavy Newport convertible I use as a cruiser and freeway runner. Any suggestions?

Not sure if the cam specs are listed correct but that's not relevant here. An 8:1 aluminum-headed motor is going to want a plug hot enough to survive the surface of our sun IMO. This is a general guide the particular manufacturer is a matter of choice but I'd also hunt for an extended reach plug.

NGK #5 or #6, I would try the # 6 first and go from there, way better to start with colder plug when testing new combinations

Actually tis engine has a few thousand on it, just wondering if I'm running the right heat range for my plugs. Last set was some Autolite 3924's.

Do you have a picture of one, hopefully #7?
Autolite # 3924 should be a 3/4 reach plug with a 5/8 socket size, not correct for stock iron heads
I am breaking a pump gas iron headed motor now for a local customer, I put a set of Champion RJ86Y in it
I was hoping to find some Champion RJ12YC or maybe even some RJ14YC or RJ10YC but no hope in my current stock

With that low of compression 8.2-1

NGK 7938 - BKR5E

Ordered a set of BKR5E-11.

Do you know how cold the # 11 are ?
Probably work great in a high compression blown or turbo charged motor with 12+ lbs. of boost on gasoline

BKR6E-11 Are what I have in there now, they are one heat range colder than the ones I want to put in.


Dave

Is the 6# or the 11# the heat range on hose plugs.
I don't use NGK, Autolites or Champions for me

The #6 is the heat range and the 11 is the gap. #5 would be one step hotter