2001 Pontiac Trans Am Intake Manifold Nitrous Install - F.A.S.T. On The Gas

F.A.S.T. was also kind enough to supply one of its billet aluminum, 78mm LSX Throttle Bodies, PN 30-54016 ($561). A 90mm version is also available to fit the corresponding LSX manifold. This 78mm version will also fit the stock intake manifold, and it can be seen in this photo how its opening dwarfs the original-equipment 75-mm unit. That's 8.2 percent more cross-sectional area for air to flow through. Plus, the entry is far more nicely radiused about the PCV and IAC holes and therefore not as disruptive to air flow.

The F.A.S.T. throttle body accepts the stock idle air control (IAC) motor and throttle position sensor (TPS), but the IAC must be rotated 180 degrees from its stock mounting orientation to fit. At this point, the throttle stop screw (on the opposite side of the throttle body) needs to be adjusted so that when closed, the mechanism is just resting on the stop screw and the throttle body blades are not contacting the interior of the throttle body.

With the throttle body bolted to the LSX intake manifold, we discovered that as the throttle was opened, the throttle bell crank contacted the grey plastic of the manifold near the Allen-head bolt seen here. This was easily remedied by loosening the set screw behind the bell crank and sliding the bell crank outward a touch.

The final step before installing the LSX manifold assembly is putting the rubber port seals in place. There are no gaskets to scrape like with previous-generation small blocks, just lube the seals with a bit of clean engine oil. Visible here are the nitrous nozzles peeking out of the wall of the intake runner, aimed to shoot nitrous and fuel right down the intake port of the cylinder head.

Just like during manifold removal, the rear-most intake bolts need to be slightly held up. We again used duct tape, but small lengths of rubber hose slit lengthwise will also work. One of the few brackets being reused with the LSX intake is the one seen here. Note that at the rear of the manifold are the connections for the brake booster hose and MAP sensor; another nipple for a vacuum hose is in the far side and not visible here.

Here's the manifold absolute pressure (MAP) sensor that's going to pop into the hole at the rear of the LSX manifold. Getting it in there would have been a lot easier with a small extension to the wiring harness, as the sucker just reaches where it ends up having to go. One can also see here the black oil pressure sending unit that the brake booster hose nipple must clear up and over before the manifold can be laid down onto the engine.

The fun begins! Getting the LSX manifold to go on was one of the more frustrating jobs this experienced mechanic has ever had to do. The fault is primarily with GM for making the rear of the engine so very inaccessible. There are a plethora of wires and hoses in the way back there, making the process of connecting everything up even more frustrating. The MAP sensor popped out of its hole countless times before we were able to orient some PCV hoses to press down on it and hold it in place.

Another example of the under-cowl headaches experienced is the vacuum lines at the passenger-side rear of the manifold. We found that one of these lines needed to be extended with some vacuum hose to get them all to join up at a rubber tee fitting that connects to the manifold's vacuum nipple. None of those items are visible here because taking a photograph of that location is physically impossible. Fortunately, getting one's hands back there is only borderline unattainable.

As the manifold bolts are torqued down one will see the manifold get pulled to the cylinder head surfaces as they are tightened. After this, the fuel rail and injectors can be popped and tightened back into place. Clean engine oil needs to be used on the injector O-rings to get them to slide in and seal. If this car were equipped with EGR, now would also be the time to reconnect it (a hole at the top of the manifold, just aft of the throttle body, would have to have been drilled earlier).

Since the LSX throttle body has no provision for coolant to flow through it, F.A.S.T.'s instructions advised us that we could either join the lines together or cap off both ends. According to TT Performance, this coolant vent line can't be capped off because, for one thing, it allows air bubbles to escape from the highest point in the cooling system (the cylinder heads) and flow to the radiator. We had originally capped this line and it leaked when the engine got warm after having been exposed to a couple of dyno passes. The crappy part is that a special adapter is required to join the lines since they are of totally different diameters. A 1/4- to 5/16-inch adapter should do the trick.

With the stock throttle cable and bracket reattached to the manifold and throttle body, the cable needs to be adjusted. This inline adjuster pops open as shown to give more slack to the cable. With the throttle stop screw resting on its stop, pop the inline adjuster back together and it should be fine. Have someone in the car push the gas pedal to the floor and make sure the throttle blades fully open to the same point that you can turn the throttle bell crank to by hand. The throttle blades may not appear to be fully open at this point, but they are.

Getting back to the nitrous system installation, ZEX includes four "distribution blocks," which are fed from the solenoids and send the exact same amount of nitrous or fuel to all cylinders in that cylinder bank. Custom-length 3AN lines lead from each distribution block to the nozzles. One of the four lines coming out of each distribution block is longer than the others; it will feed the rear cylinder on the driver-side distribution blocks and front cylinder on the passenger-side distribution blocks.

Before attaching the fuel and nitrous distribution lines to the nozzles, the nozzle jets need to be set in place. For our 125hp setting, ZEX recommended a 21 (0.021-inch orifice) nitrous jet and a 17 fuel jet. The red distribution lines will go to the "fuel" fitting and the purple lines to the "nitrous" fitting. Watch that the jets don't fall out as you are connecting the lines.

As the distribution lines are connected, it's important to hold the jet fitting with a 3/8-inch wrench as the lines are tightened with a 7/16-inch wrench. This is impossible on some of the nozzles thanks to all kinds of crap in the way, and sometimes the nozzle itself must be held. If this must be done be careful not to over-tighten the line or the jet fitting can break (speaking from experience). Also, once fully tightened, the braided lines do not swivel, so get them all started on that cylinder bank (be careful not to cross-thread them) before finally tightening them all, or else attaching one may impede your being able to reach another.

A "crow's-foot" wrench, which attaches to a socket extension, will be invaluable in tightening a few of the lines onto the nozzles. Also, a "stubby" 7/16-inch open end fits much easier under the F-body's intrusive cowl. GM: thank you again--and my medical bills for bleeding hands and carpal tunnel treatment are in the mail. After all this, we wonder if it wouldn't have been easier to connect all the distribution lines to the nozzles prior to manifold installation; but then, making the vacuum and MAP connections at the manifold's rear may have been pushed over that fine line into full-blown impossibility.

Assembly of the nitrous and fuel solenoids comes next, with 4AN fittings (with built-in filter) installing at the inlet and 3AN tee fittings installing in the outlet. One 3AN line will go to the passenger side, and the other to the driver-side distribution block. Liquid pipe thread sealant is required on all NPT pipe threads. No Teflon tape is permitted because it can get sucked into the system, clog orifices, and possibly blow the motor. Brackets are included to help install the solenoids at a suitable location.

Making sure all braided lines will reach the distribution blocks, the solenoid brackets are bolted to a suitable location. We found that an unused hole in the front of the passenger-side cylinder head was the perfect location for a stud and nut. Note how huge these solenoids are; they can flow enough for a 300hp shot of the juice. Here, the 4AN fuel feed line (purple--not red, mysteriously enough) is being connected to the inlet of the fuel solenoid.

The other end of the fuel feed line attaches to the fuel rail's factory 4AN fitting, but first, the Schrader valve must be removed from inside using a suitable Schrader valve removal tool. Otherwise, fuel isn't going to flow out of the rail and into the line, so don't forget this step! If your fuel rail does not have such a factory fitting, ZEX supplies a 4AN to 1/8 NPT fitting that the fuel rail can be drilled and tapped for.