hot or cold plugs

What are you guys using for spark plugs that have big blocks with Edelbrock RPM Performer heads?

It depends on the mecahnical, not dynamic,compression ratio, shift RPM and fuel being used Whar are yours

NGK has the best tech line in the business--call them and they will put you dead on like a Nascar crew chief

3924's

I`m at 12.1.1 comp. and run a 7 or 8 NGK`s depending on my tune. The 7 can speckle a bit if the engine temps up there and the tune isn`t..............

It's a 505 pump gas engine with Edelbrock RPM heads. The reason I asked is I have been running Autolite AR3924's , a friend of mine runs Autolite AR3933's. I don't recall why I have been running these plugs or if I should be running something different. SO?

I only run NGK`s so not sure on those..............

The 3933 are non resitor and I think a retracted gap. The 3924 are a resitor with a extended gap, the 3933 is one step colder than 3924. IHTH

OK, so should I run a resistor or non resistor plug with MSD ignition?

try the 3924 resister plugs first. if they're too warm step down to a 3923. msd's have to have resistance in the system; whether it's the wires, ballast or plugs, or combination. an ap3924 has 5000 ohns, regular 3924 7000 ohms; tested some rc12y's at 70,000 ohms! most resistor plugs will be 5000 or more ohms. of course non-resistor should be zero. if you're by-passing the ballast then more resistance will need to be in the plugs and wires.

NGK recommends the following plugs for Edelbrock heads.
R5672A-7 is a non resistor race plug. -7 is the hottest plug they offer. -11 is the coldest one. This is a projected tip spark plug. Use R5671 for domed pistons.
BCPR6ES is a resistor type street plug.(Stock #6779) This is what I currently use on my 383 Road Runner with MSD ignition. These are available in heat ranges 4 thru 9

According to MSD website either will work just fine but you should use resistor type plugs for less radio interference if that is a concern.

msd's have to have some resistance in the system, race/street or whatever.

I'm using the 3924 in my 416 injected engine

I have been running a AR3933 plug and was thinking about running one a step hotter. Which one would that be a AR3932 or AR3934.

The 3924 is what I was told

I ran ar3934 in my 493 for years. Probably the same plugs as I dont change them. I tried ngk and champions at DW12 and went back to the ar3934 very quickly

On Autolite plugs the smaller the number the colder the plug, 3934 are the next hotter from the 3933

Everything you want to know about Autolite plugs. BTW I run AR3911s in my small blocks.

http://www.autolite.com/technical-resources/tech-specs.aspx

Do you have a link? Everything I see on their website says not to run a non-resistor plug, resistor plugs only with MSD.