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Discussion Starter #1
Hello all , i've got a 355 with double hump heads that i currently run Autolite 85 plugs in , i'm going to be putting a Nitrous kit on it , only a 100 or 150 shot , trying to decide if the plugs i have now will work , they're right in the middle of the heat range chart , anyone use them or are they too hot a plug ?
 

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Hello all , i've got a 355 with double hump heads that i currently run Autolite 85 plugs in , i'm going to be putting a Nitrous kit on it , only a 100 or 150 shot , trying to decide if the plugs i have now will work , they're right in the middle of the heat range chart , anyone use them or are they too hot a plug ?
The heat range for Autolite plugs is easy to remember. The higher the number, the hotter the plug; the lower number is colder plug etc. I would be very conservative and use two steps colder plugs to be safe with nitrous. Make sure you have a very healthy fuel pump that supplies plenty of fuel. One last thing, always turn the nitrous bottle off before shutting off the engine. Turn the bottle off, rev your engine several times to run the nitrous out. When your engine suddenly revs slower and less aggressive, you have used up the nitrous and can turn off the engine.
 

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The heat range for Autolite plugs is easy to remember. The higher the number, the hotter the plug; the lower number is colder plug etc. I would be very conservative and use two steps colder plugs to be safe with nitrous. Make sure you have a very healthy fuel pump that supplies plenty of fuel. One last thing, always turn the nitrous bottle off before shutting off the engine. Turn the bottle off, rev your engine several times to run the nitrous out. When your engine suddenly revs slower and less aggressive, you have used up the nitrous and can turn off the engine.
If you haven't used nitrous before, make sure to read up on important tips. Things like retarding your total timing a number of degrees depending on your nitrous level. For a 100 shot, I would retard the timing 3-4 degrees to be on the safe side with cast iron heads.
 

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NGK makes the best spark plugs for a performance engine. They aren’t expensive, and I don’t know what is different about them.
The most and only important feature is, they seem to resist carbon fouling better, allowing you to use a colder than normal heat range. Critical in a NOS situation on a street/ strip car, where you may not be willing to pull the plugs and read them several times.
You have closed chamber heads, good because you probably don’t have the base timing cranked up excessively. But your base cylinder pressure is going to be higher ( this is why these engines run better than the open chamber, lazy heads), so it might be less forgiving of an improper tune.
All the nitrous kits are adjustable, my only advice would be to start with the smallest jets, even a 100hp will give you a very impressive torque boost at lower rpm. And an electric fuel pump will give you a stable fuel pressure level, independent of the engine rpm.
 

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It has been years since I messed with nitrous but I can tell you some of the things we used to do to keep the engine safe. The main thing is to always remember to think of the nitrous as the icing on the cake. It is meant to be used as a power adder. It is addictive. Most people start out with just a little shot and when they see how much fun it is they start bumping it up and up until they are totally out of the ballpark from where they started. It is going to increase the burn rate in the cylinder which means that if things aren't right and managed it is going to hurt parts. Things like colder plugs, less timing and fuel management are important. The bigger the shot the better your internal engine parts have to be also.

We used to mount a one gallon fuel cell with a extra electric fuel pump to make our nitrous stand alone. We didn't use the pump that runs the car for the nitrous. Later we used retard features that would retard the timing when the nitrous was activated. We used to put a 225 big shot plate under a rons toilet on alcohol. The coolness in the intake with the alcohol with the increased burn rate of the nitrous with gasoline was wild. It would take a mild mannered bracket car and turn it into something that would tote the tires head high when it left. The alcohol helped to keep it from detonation which is what causes a lot of problems with nitrous.
 

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On my Street Stock PU, with a tiny 75hp hidden kit, I also used a stand alone fuel system with aviation fuel, and a electric fuel pump that fed only the nitrous kit. It was a completely fool proof setup, and worked flawlessly. That 75hp was an easy 120 ft/lbs of torque at about 3000 rpm, it was absolutely noticeable, in that it came on instantly. This would really help a Street car with not enough rear gear and/or converter.
 

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Discussion Starter #7
Thanks for the responses guys , i the system i've got is a NX plate system with a stand alone 1 gallon cell and electric pump , i also got a MSD start and step so i can pull timing out , i'll check into the NGK plugs to see about a cross reference , thanks
 

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Discussion Starter #9
i was thinking NGK myself , i've been looking all over trying to find a cross reference from a Autolite 86 to NGK (than 1 heat range colder) but all i see is XR4 or 2911 which are a heat range 4 which is on the hot end , anyone know of a colder plug that will fit ?
 
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