Can anyone tell me what plug I should be using in a 500 inch 440 base motor with edelbrock performer rpm heads? It has a comp cam 256@50 266@50 with 550 and 570 lift. Has a edelbrock torker II single 4 holley 950 hp. And any ideas on jetting and power valve? Thanks for the help.

been some good threads on plugs (brand as quality has deteriorated). I'd say 1 or 2 heat ranges colder than stock OE for a start. street or strip? what DCR?

My 446 ci 500hp and 535 torque with Eddy heads likes NGK BCP6ES.

Two things to do is to see if you can sell tha Toker 11 and buy a Eddy Performer RPM intake and then start with the stock Holley jetting for your carb. that it came with I select my power valves based on how much manifold vacume the motor has at idle RPM in gear, if it has 8.5+ inches of vacume I will use a Holley 6.5 power, if it has 6.5 inches or more I wll use a 4.5 P.V., I shoot for at least two inches less on the P.V. rating than the manifold vacume is The reason I use this method is most stock Holley carbs won't idle well enough on the idle circuits only with a big cam so most people adjust the throttle plates so there not on the idle circuit only, there into the transition circuits which can and will affect the opening of the power valves IHTHs BTW, most single plane inatkes are very lazy to the throttle responce under 2500 RPM, the Performer RPM are not that way I've dyn tested both of those intakes on the same motor 20 minutes apart and then tested a Mopar M1 single plane 35 minutes later, I use the same carb. on all three intakes and then put the Performer RPM back on for the street use As far as spark plugs I've use both the Champion RC12YC and RC9YC and the Autolite 3924 and 3923 for pump gas applications, the compression ratio and fuel used will determine which plug works best for you IHTHs

thanks for the help guys I really appreciate your advice. I just bought this car and know very little about it. And I never had a aluminum headed motor.Car is popping and banging out the exhaust so pulled plugs and they are black. Has msd 6 al and had rc9yc4 plugs in it. not sure about the jets in the carb or power valves.

I'd go thru everything that could be making it run rich; choke/jetting/PV/ and plugs/plug wires/firing order/MSD itself. If they are all black you could do above checks then get a set of 12's (not too cold/not too hot) & change out 1 plug at a time & when you find the change (problem) that lets that plug stay a nice tan then toss the rest of em in (& post what it was)

Hello guys thanks again for all the help, looked at the wires and found number 5 burnt and hard and cracked open. Replaced it and all plugs to 3923 like cab said. It sounds a lot better but still does not like to idle can you give me a baseline on jets and power valves for older 950 hp. cam is 256 266 @50. 550 570 lift flat tappet. 10.0 compression. msd chrys dis. no outlets to check idle vacuum. Thanks again