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Discussion Starter · #1 ·
I have an iron headed 406 sbc with a cheater plate. I am running the NOS jetting 63/71 for a 150 shot. Flowed the fuel pressure at 5.5 and it still is popping on the nitrous. I run about 950 bottle pressure and it acts like its still fat. I am trying to make sure my tune is right cause its got hyper pistons for now. Any help would be appreciated. If you need more info just let me know.
 

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Square the jets and try 6lbs fuel, I never use NOS jet spreads.

How much timing are you pulling out on the Hit, 5-6* should be more than enough.

If you dont have any more jets you can swap place with the nos and fuel jets putting the 71 on the nos side and use about 7to7 1/2 lbs pressure and drop from there to clean it up.
 

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Different engines like different tunes, I have ran NOS tunes before, but my luck has been better with square jetting. I have never seen a recomended flowing fuel rate from NOS, dont know if they dont include it with their plates or not, but with the recomended jet spreads I have had to run extremley low flowing fuel settings to clean it up. I believe the ability to run higher fuel pressure by squaring the jets or even going 10 sizes bigger on the nos side, gives a better mixture of the nos and fuel. IMO
 

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Discussion Starter · #7 ·
So maybe I should bump it up a little. I want to try to stay around the 150hp range and will try the square jetting with 6lbs of fuel. i am not trying to sound like an idiot. I know i needed to get some advice from some people who know about this.
 

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Discussion Starter · #13 ·
Well after talking with Steve I replaced the nitrous solenoid and the magnet was cracked on my old one. The car is still popping and the plugs don't look like its way rich but it sounds like it. I flowed the nitrous again and it was still good. Its definitely hitting harder now but the popping I just can't figure out. I thought maybe it was an ignition miss and the nitrous was making it worse. I changed the cap, rotor, wires, coil, and module and its still doing it. I am really lost on what to do. I would think it should at least run on the NOS tune.
 

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What is your compression ratio?
What is your plug gap?
What ignition system?

I have a 6 series ignition and had a similar plroblem. My 410 needed a .035" plug gap from a .045. I also had to go from a .032" hi air bleed to a .025" and jet down the main jets accordingly as my mid rpm fuel was too fat. I also had to raise the 1-2 shift up 500rpm.

Not sure if all this will help but it did mine and the motor is happy now...even on the spray this past weekend. (had to close the plug gap even more to .030")
 

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Discussion Starter · #20 ·
The motor is nothing special. Small hyd flat tappet cam. I think its about 488 lift. 750 holley mechanical secondaries. Flat top pistons. Slighlty ported 72cc double hump heads. Weiand single plane intake. It has a stock HEI with some brand new MSD super conductor wires and two stage colder plugs (I ran it with two different heat ranges and they both ran the same.) I ran it at 950psi bottle pressure and 5.5psi flowing fuel pressure. I bought the car with the motor in it and it had just been built.
 
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