ThayerY

Hello everyone, I'm planning on adding nitrous to my 88 Trans Am project car but I'm pretty new to the world of performance mods, especially nitrous. I've done some research and I'm hoping to do a 125hp shot, but I'm not sure what kit I should go with. I will do a compression and leakdown test before adding nitrous, and ensure that the fuel pump is up to snuff. The car was originally someone else's project before I bought it (he was older and had too many projects and not enough time) but he really knew his stuff and I trust any work that he did to the car. Here's some info about the car and what's been done to it so hopefully you can help point me in the right direction.

-Originally a 305 TPI but now has a 350 TPI swapped in from a 1990 Firebird Formula.
-Has an upgraded cam (nothing crazy) and 3 inch headers along with a cat back Magnaflow exhaust.
-All new springs, struts, shocks, brushings, brakes, etc... and posi-traction.

So given that info what kit would you recommend for a 125 shot? What spark plugs? Is there anything else I should replace or add? Timing (variable? since I wont be running it on nitrous super often)? Is a tune needed?
I also want to have a purge kit, and I'm planning on purging out the side vents on the fenders on each side.

Thanks for reading, any advice is appreciated.

IROCZman15

iTrader: (25)

NOS makes a pretty inclusive kit for this:

https://www.holley.com/products/nitr...parts/05151NOS

I ran this kit on my tpi 305 for about 5 years using mostly the 100 shot jets, and a few times I ran a 150 shot.
-I now use the same solenoids on my 406 sbc setup, NOS told me directly that the fuel solenoid can flow to 200 hp and 175 hp on the nitrous solenoid)

Make sure you have a way to retard timing when spraying the nitrous. retard 2 degrees for every 50 hp shot you are spraying. I used to use a MSD Digital-6Plus box with the 305 tpi setup. Now I use a Holley Hyperspark ignition box to pull timing. For a 125 shot, you would pull 5 or 6 degrees.

Make sure your fuel pump, lines, fittings, are not at the end of their lifespan and in good working order. Think about having a bottle heater also. I overlooked this for many years until just recently when I realized how important 950-1000 psi bottle pressure actually is.

As for a purge setup, NOS(Holley) also makes a simple kit,
https://www.holley.com/products/nitr...parts/16030NOS
but there are a few other companies you could use too: Nitrous Express and Nitrous Outlet are the other two big ones.

ThayerY

Thanks for the detailed response and links! The NOS kit you linked seems like what I'm looking for however, it only has 100 and 150 shot jets. From what I've read a 150 shot is the max you would want to do on a mostly stock small block which is why I was going to do 125 to be safer. Guess I'll have to round up or down if I get this kit (or get a 125 jet that fits it, which I assume is possible).

The only further questions I can think of right now are about the ignition box. Do the two that you mentioned automatically retard the timing when nitrous is engaged, or do you have to change it yourself if you plan on spraying? If so, would that be something you adjust from the engine bay, or can you do it within the cabin? Maybe these are silly questions, but most of my mechanical experience to this point has been repairing and replacing parts, not upgrades or changes like messing with timing.

Thanks again

IROCZman15

iTrader: (25)

Yea, don't worry about only 100 and 150 jets. Jets cost $5 a piece usually so you can do the math and make it a 133 shot, or 104 shot, etc. There are jet charts online, and even some online-robot jet calculators to help you. You should know what your fuel pressure is ACTUALLY at.. not what it "should be, but know what exact fuel pressure your individual system currently is at.

There are many CD boxes (ignition boxes) some old school and some new and digital. They all come with wiring diagrams on how to have the ignition box specifically retard timing when the nitrous is activated. In short, you splice one of the ignition box trigger wires to the nitrous wiring and it pulls the amount of timing that you dictate. The MSD digital 6 plus box could retard timing in the tenths of a degree, so for instance if you wanted to pull 4.8 degrees, it could do that. The adjustments are done at the box, usually on the side of the box there are dials, or pills, or whatever. My hyperspark box is specific to the sniper efi, so I make timing adjustments in the cabin, either on the holley efi touchscreen, or on my laptop. if you google an image of a cd ignition box, you will see the features, and if you go to the specs or features info, you can even read about how to wire it up.

vorteciroc

Some General "rules" to follow for a relatively stock Non-Vortec, Roller-Camshaft, Gen-I SBC...
This way, you do not "Blow Up" or "Melt Down" your Engine (Unless that is your Goal).


-ONLY use a "Wet" System.
-ONLY use a Mixture Injection Plate for TBI Fuel-Injection (Do NOT use a Nozzle in front of the TBI Unit).
-Use the highest rated Octane Gasoline that is available in your location (If 93 is not available, lots of "Booster" will help).
-Upgrade the stock Electric Fuel-Pump (Add 50% more flow. Fuel will be your "Best-Friend" in preventing an Engine "Melt-Down").
-Obtain 2 Adjustable Fuel Pressure Regulators (1 for the Fuel Injectors, and 1 for the Nitrous-System Fuel-Solenoid).
-Obtain a MSD 6AL Ignition Module (for CD-Ignition and a Rev-Limiter. You MUST use a Rev-Limiter).
-Obtain a MSD Ignition-Retard Module (pull 2 Degrees for Initial Timing, and 2 more for every 50 HP added).
-Use the same Spark-Plugs but 1 temperature range lower. Or use Spark-Plugs without as much of a projected-tip.
-Close the Spark-Plug Gap by 0.010". Going with a 0.025" Gap is probably ideal for your Engine.
-Obtain a MSD Window-Switch to control Nitrous activation (never activate below 3,000 RPM, and deactivate 500 RPM before max HP/ red-line).
-If Jetting for more than 100 HP... increase the activation RPM to 4,000 RPM (Not 3,000 RPM, try to save the Connecting-Rods).
-Obtain a Throttle-Linkage Micro-Switch (Only connects the Solenoid Circuit under Full-Throttle.
-NEVER activate a Nitrous System without being at Full-Throttle.
-Install a momentary Button that is in a location where you can hold-down the button and still steer the Car comfortably.
-Install the Bottle in the "Stowage Compartment" with a "Blow-Down" Tube through the Floor (use a very snug fitting floor Grommet).
-Use a "Quarter-Turn" "Emergency Shut-Off" Valve, that is placed with in reach in case of a Bottle-Valve Failure.
-If Nitrous fills the Passenger Compartment, it will quickly displace all oxygen, and you will Pass-Out and crash!

There are tons of other rules and tricks... but these should be the minimum.
Nitrous accidents do not happen often... but when they do, they are very bad!
I have been passed out from Nitrous, while on fire from methanol.
Methanol Flames are not visible in day-light (does not burn bright orange like Gasoline).
No one could see that I was on fire, until about 3 minutes later when my fire-suit was melting-off very quickly.
Do NOT make my mistakes, learn from them!


Good luck, and have fun!

ironwill

In that case, tread lightly, and follow all the instructions and advice offered both by your kit manufacturer as well as that of those ^^^^ above who have been there/done that. Nitrous, while being a relatively easy and inexpensive path to an extra 100+ hp, it can also be The Killer of Engines if installed incorrectly or used improperly.

ThayerY

Ok thanks! This is a bit to wrap my head around, but I'm sure I'll be able to figure it out. I've done some robotics wiring/programming in the past...

Good to know they should come with wiring diagrams, I've had my fair share of parts with no instructions anywhere to be found.

ThayerY

Will do! I'm going to be very careful and put in the extra money to have safety shutoffs and stuff because I am really in no position to be replacing an engine anytime soon.

ThayerY

Thanks for the comprehensive list! That's a lot to figure out, but I'll get there eventually. Maybe I'll also look around for someone who has installed Nitrous before in my area to help, but unfortunately I'm pretty rural so there's not a performance shop or anything near by.