Best Spark Plugs for 605 Hemi

All,

What spark plugs would you recommend for my 605 Aluminum Hemi, it has the Indy (race) 426-RA1 heads, 11:1 CR, 655 Lift w/272/280 Duration & R110. I also have the Holley HP ECU with MPFI Sequential, MSD Digital 6 Ignition, MSD Wires.

It is a Street/Strip car, but mostly street, 4.10 Gears, and not a highway car. The engine Dyno’ed at 950HP @ 6400 RPM with and 1150 CFM Demon Carb, and smaller -2 Intake.

I currently am running the Holley HP.

Any ideas would be of great help, and Thank you!

Regards, Mark

I run a NGK 6 heat range with my 11:1 pump gas engines so that is what I'd start with. You might want to go one step colder if you are going to really beat on the engine.

Call the NGK tech line and see what they say. My guess is that they'll tell you the same thing.

Hi Andy,

Do you have a NGK Plug Number? The reach is the same as an Edelbrock 440 performer RPM Heads.

Would you recommend an extended reach plug?

Thank you!

I'd probably start with something cheap to see if it works. #6779 plugs are only $1.59 each from Summit and they should work. They have a wide gap and a projected tip. If your EFI system is dialed in properly those plugs should work. Try them and see how they look. They are cheap enough that you can toss them if they don't work and try something else. I think these plugs are OEM on Jeeps but I'm not positive.

I rn a NKG 6 heat range in my 605.

I have used several "racing" plugs.Used to use champs all the time back in the day.I use the NGK at $20 A SET.Also installed sooty plugs that were from an overly rich condition and they came out and read accuratlely.

Hemi-itis,

What plug part numbers are those, as I think I would like to try those.

Thank you for the picture!

Mark

I can check the PN next time I'm down at the shop.The 8 heat range worked for that combo on pump gas.I suggest you determine which PN you need and get 3 sets with 3 heat ranges say like 7,8 & 9.Plug reading must be done by clicking off the ignition at WOT at least at the top of 2nd gear AT or 3rd ith manual.
Making a pass at the track click off over the stripe at WOT.If you drive back to your pit it will nullify the plug reading.You would like the change in color on the strap to be at the elbow.

Guess the shut off at the stripe deal MAY be best but you can still read em even when cruised on at least w/my carbs. Now the blubbery 3-circuit stuff especially on a street car makes sense..........

I like to work on one circuit at a time on my carbs, idle first, then transition, then part throttle cruise and then squirter and WOT jetting for the best mph results at the track in the 1/4 mile
OP, having a good wide ban on the car is a big help
As far as spark plug heat range on your deal on pump gas I would try Champion RN9YC or RC9YC and in Autolite # 3924 or 3923

I use NGK R5671A-8 (4554) in my 11:1 pumpgas 572" hemi when I'm not using nitrous. I go one colder on the spray.

An8sec70cuda,

I was told that I need to use a Resistor plug because I have both an MSD Box, and Holley EFI.

I called the NGK number, and they recommended this plug: BKR6E/6962

It is a V-Power Nickel, that is Resistor. He told me that I could go one colder if this plug is too hot.

I ordered a set from Summit, and will let you know the results.

I have had good results in the past with BR8EGV plugs, but those were on smaller displacement engines. I may also try those as well at some point...

Mark

Have you tried 7's w/that low compression or is the Hemi sensitive to where it needs the colder plug............

lockjaw...hope it works out for you!

thumper...nope, never ran anything but the -8s in it on motor. Hemis are supposed to be more forgiving on pump gas than a wedge. Never had any problems w/ fouling them out or anything and they seem to work fine. Never saw a need to change.

Exactly what I thought they would recommend. #6 seems to work just fine with 11:1 compression and EFI since that is what most of the OEMs use. Like they say, if you see any issues at WOT you can always switch to a #7 plug but I don't think you'll have a problem as long as your EFI is dialed in.

With the last 5 year go round, the #8 put the color change in a good spot on the strap.That was 7.4:1 CR and 12 lbs of boost,new pistons are 9:1 so it's back to the tuning thing.............
Pump gas might be no more than 3 lbs.

The last pump gas 10:71 blown street Hemi stroker motor 484 C.I.made 924 HP at 7300 RPM on CA pump swill with 7.0 lbs. of boost and 33 degrees total timing with two Carb. Shop blower Dominator carbs.
I made it have 9.3 to 1 static compression ratio so we wouldn't have to run more boost and heat up the intake manifold temps. to make 900 + HP on 91 octane CA pump swill back in 2002
How much power can your chassis handle now