i picked up a complete NOS 100 shot nitrous kit from my boss for next to nothing and my question is what modifications should i do to my big block ford 390 to be able to use it without worrying about my motor. I already rebuilt the motor but don't want to have to worry about hurting it. Thanks, Matt

 

Make sure that you have a big enough fuel system to handle the nitrous. I am assuming that it is a wet kit.... As long as your jetting is fine there shouldn't be a problem. Always test your fuel solenoid before you spray the nitrous as N2O without fuel is a BAD thing. A WOT switch, window switch and fuel pressure safety switch are essential safety parts. A bottle heater with a pressure based thermostat such as the one from DynoTuneUSA is a good thing to have as it keeps your bottle pressure constant. Make sure that you do a complete tuneup on the motor before you spray. Buy copper core spark plugs 1 or 2 ranges colder than what you have now. Pull 2 degrees of timing for every 50hp of nitrous that you plan on spraying. I've found that the Mallory 685 is perfect for nitrous as it has a rpm activated window switch as well as the ability to pull timing when the nitrous is activated. Its easily programmed with a digital display for the rev limiter, switch activation rpm, timing retard, etc.

 

Forgot to add that a wideband O2 sensor or at least access to one is a very very valuable tool when tweaking your jetting for the nitrous and fuel.

 

Bolt on a set of headers. I dont think you'll hurt a 390 with a 100 shot. If you used a smallish cam, it would probably be wise to delay activation until after about 2500rpm, to avoid excessive cylinder pressures at low rpm.

 

You generally don't want to start spraying until 3000rpm and usually stop 200rpm or so before you shift. The reason for not spraying until 3k is that when you are at lower RPMs there is not enough air movement through the engine so you run the risk of damaging the motor.

 

Hey guys, the man has a 390. I don't see any stats but i'll assume it is an old carb engine, no electronics. He should have no problem as long as its' compression wasn't bumped up too high and sprays around 3g as you stated. Whutchathink?

 

Even a stock 390 that's not rattling or anything should laugh at a 100 shot...

he'll be fine.

 

Right, but the parts I mentioned are still necessary whether its a fuel injected motor or carbed

 

It is in fact a carbeurated engine, came out of a 75 ford pickup. I rebuilt it with a few modifications including a .533/.533 camshaft, 428 cobra jet stainless valves, and new hypereutectic pistons. Other than that the engine will have headers and it has a holley street dominator intake manifold on it with a 650 cfm holley on it. Maybe that will help you guys out to know that stuff too! Thanks, Matt

 

Yup, read my posts above. Tuned properly, I wouldn't hesitate to throw a 150 jet on it.