View Full Version : Building for nitrous

Pro-touring towncar
08-20-2004, 05:34 PM
I have contected the nitrous manufacturers but never could get an answer.
What do you need to do to your motor to have a big hit of nitrous and live? I am looking at about 2-300 horse hit. maybe more.

Please help.


Ralph LoGrasso
08-20-2004, 06:01 PM
Forged internals would be a good start.

08-21-2004, 11:50 AM
I'm no expert but, from everything that I have read, the bottom end should be built to handle the total amount of power output desired....example: you want 600hp with the 2-300 shot of nitrous, then the crank/connecting rods/pistons etc... should be strong enough peices to support at least 600 hp. I have also read that the cyl. heads have to flow really well on the intake and exhaust sides in order to get all the burned gasses out or the nitrous will build up in the cylinders and kabloowie! :doh:

also with that big of a nitrous shot, you may want to "o" ring the block where the cyl. head bolt on so you don't blow a gasket :fart:

anyone feel free to correct me if I am wrong. :box:

08-24-2004, 02:13 PM
So i am no expert on exactly what you need either. I would suggest a Mustang board as they all seem to use NOS. I can tell you, as Ralph said, forged pistons are a must, but otherwise, I have broke the rules and run 250HP on some pretty mild bottom ends with stock cast crank and baby rods. But, again, I have no idea what a Ford will need.
Keep in mind with nitrous, its all about fuel pressure. You have to keep good fuel pressure, and prevent going lean, or else you can go boom!

Pro-touring towncar
08-24-2004, 05:36 PM
that is one thing I defianatly will be doing is adding a seperate fuel pump etc for the nitrous system.


09-06-2004, 09:00 AM
While you can run a 300 hit on a fairly mild bottom end, eventually its gonna let go in a big way. For a motor that will take the hit time after time;

Forged pistons are a must. Good rods (forged or billet) are a must. Avoid long rod setups for big NOS use. A well done cast crank will be fine, but a forging would be preferrable. I would go with a studded bottom end. Make sure the block decks are flat as well as the heads and use a good gasket with head studs.

At 300 hp you dont need to do anything special with bearings, clearances or ring type. You might want to add a little end clearance to the rings to allow for more expansion. Stainless valves would be a good idea, but not a requirement.

If youre current fuel system cant deliver enough fuel, a seperate system is youre only option. Start jetting with the fuel side a little rich. Nothing can break parts faster than an NOS lean out.

You must use an ignition retard at these NOS power levels. At 300 HP you want to pull around 6 degrees out of the total timing advanve.

For safety, its a good idea to use a WOT switch, a fuel pressure sensor (placed right at the fuel solenoid) and an RPM window switch that only allows the NOS to be activated between a fixed set of RPM points (over 3000 and shut off at 6500). Run the bottle vent tube OUTSIDE of the car.

Lastly there is the day to day living with NOS. NEVER leave the bottle open when you park the car. Re-read the last line. Get lazy here and you will regret it. Leave the bottle closed until you want to use it. Close the bottle when you are done. I wont use the automatic openers cause I dont trust them. Manually closing the bottle valve is the only way to know for sure its closed.

If the bottle is left open, a small undetectible leak in the engine NOS solenoid, over time, will fill the intake manifold. Some of the intake valves will be open. Those cylinders will fill with NOS. Some of those cylinders will be in overlap. Those cylinders will fill the exhaust system. Some cylinders will have open exhaust valves. They will fill with NOS when the exhaust system fills. You come out in the morning, go to start the car and BANG!!!! Youre intake manifold just went thru the hood and out the garage roof. And it can be much worse.

On my car I have a purge circuit. By flipping a switch I can disable the MSD box and coil, hold the throttle wide open and spin the motor for ~10 seconds. This blows any built up NOS out of the motor prior to ignition.

10-04-2004, 03:24 PM
SDMAN so do you just spin the motor over by cranking it with no ignition? isnt there a chance of it flooding if you do this? how did you set this system up?

10-04-2004, 06:20 PM
Just put a switch on the hot wire to the distributor so there is no power to the distributor = no spark, until you turn the switch on. A lot of high horse / big timing motors also use this to help avoid kick back.

10-05-2004, 04:08 AM
Okay, the timing issue-you want to pull out 12 degrees out if you run a 300-shot...remember, 2 degrees for every 50/shot is a good starting point. Next, above a 200/shot ring selection does matter. Speed Pro among others make rings specifically for nitrous. They use pistons forged with a lower top ring so that the piston crown absorbs more of the "hit" instead of the top ring which can flutter violently to the point of breaking when you hit the 'gas. I would also recommend having the piston tops coated to resist creating "hot-spots" which can lead to pre-igntion-REALLY not good with nitrous use either. Next, don't skimp on the ignition controls-with extreme though temporary cylinder pressures, I'd go with a digital box with timing retard functions in addition to NOS's timing retard and progressive controllers. As for a fuel system diagram, you can easily find them on various NOS boards. Nitrous is mean stuff whcih is why I'm going the route of a turbo for my next project. -Jabin

10-05-2004, 06:20 AM
Okay, the timing issue-you want to pull out 12 degrees out if you run a 300-shot...remember, 2 degrees for every 50/shot is a good starting point. -Jabin

Agreed, actually even more in some engines that run a lot of timing. We pull out 15 at 300, but we also run 40 degrees locked out.

10-10-2004, 12:11 AM
Just remember stock 5.0 blocks seem to start splitting at about 500hp. :hmm: From what I've done and seen it's hard to keep one together with that much hp. Occasional use will of course make it last longer. they are cheap and easy to build and I love the crap out of 5.0's but something to think about.

10-15-2004, 02:08 PM
Wait-you have an HO302 in that Lincoln, right? If memory serves right (and maybe not...) 1991-up HO302's had cast cranks/rods whereas 1987-1990 HO302's featured forged crank/rods. I would think 500 hp with a short stroke, forged rotating assembly and hydraulic valvetrain should hold up fine if the motor is healthy to begin with. Ignition controls/unrestrictive exhaust is the key. -Jabin

Pro-touring towncar
10-17-2004, 10:20 AM
Unfortunatly the 89 is the lo-po engine. flat-tops with no valve reliefs, so that I am restricted on what I can do with this motor. But the block is the same so it is a good starting point. I may even start from scratch with a rebuilder HO motor and go from there. I also my just go with a forced induction system.