So you want to race your GMC Syclone or Typhoon?
Before you race your truck, you need to make sure it is running upto par, please make sure that you do the reliability mods first. You should expect a stock Syclone with a properly boosted launch to run 13.3-13.7 and a stock Typhoon to run 13.8-14.2 1/4 mile time. Higher Temperatures and Altitude may affect your results. If your way off, you most likely have some tuning issues that need to be resolved.
So now to the fun stuff, you bought a Syclone & Typhoon because of its performance. It was quickest pickup and SUV of its day, and in still holds well when being compared to vehicles 15 years newer. They are quick when normally launched. If boost launched correctly, they are force to be reckoned with at stop lights. Warning: Boosted Launches are fun, addicting, and will eventually break stock parts. I will get into what it breaks later and what can be upgraded to keep that smile on your face.
How to do a boosted launch:
- Put the transmission in (N) Neutral
- Rev the engine a couple of time while simultaneously pushing down HARD on the brakes. Revving the engine creates vacuum for the brakes.
- You should feel the Brake Pedal drop lower
- Keep the brake all the way depressed, and shift the transmission into Drive (not Overdrive).
- Start pressing on the gas pedal now to build up boost, it take a little while to get past 0-1 psi.
- When the boost is where you want it and it is time to hold on and go, release the brake and slam the gas at the same time.
- Typically stock Syclones like 4-6psi, Typhoon a little higher. Try launching at different levels to see which works best with your truck. You want a little chirp from the tires but not a lot of wheel spin.
I do not recommend doing 2 boost launches right in a row, because the transmission temperature will get dangerously high especially if you do not have additional transmisson coolers. If you can't hold 5 psi brake torquing with your truck you have a brake issue to resolve. If it pushing through the brakes, its often the front brakes. Often the front brakes fix is as simple as bleeding the brakes or replace the worn parts. If the rear tires are spinning, I would try upgrading to 7/8 wheel cylinders. If you want additional holding power, buy two set of soft non lifetime brake shoes, use both of the longer primary shoes, and give the drums fresh turn.
If your racing at the track. Don't worry about your reaction time, it doesn't affect your ET. The above boosted launch procedure takes time and some track will start the lights lights before you have to time to finish the procedure. This procedure can help your Elaspe Times by 1/2 second. If you have the stock chip, you need to go WOT before you race or you will be boost limited to 9 psi ; you can over ride this while revving in neutral to set the brakes. Slightly modified trucks may need to shift into OD at the end of the track, just remember to do it manually when you hit 4500-4600 rpm in 3rd gear or just before 100mph with the stock motor.
Things that break during a boost launch and how to upgrade them.
- Motor Mounts
- The original stock motor mounts by now are old and brittle; with a few boost launches they are just waiting to break, particularly the driver side mount. Some signs of a broken mount is a broken fan shroud and/or chaffed upper radiator hose from the alternator hitting it. You can check you motor mount by leaving the hood open and brake torquing in Drive, while watching the small opening at the engine. Please be careful while doing this and use common sense, you don't need to build boost, a few second is all that is needed to test the mounts. The engine normally will move upward less than an inch, if the motor mount is broken it be move quite a bit, it will be obvious. You can temporarily fix this with an engine tie down. You can try searching for a different engine tie downs on http://www.syty.net. You may want to be proactive and add an engine tie down before the mount breaks. The permanent fix is new motor mounts and I would highly recommend using solid mounts, not replacement rubber mounts, so this is never is a problem again.
- Propshaft
- The stock propshaft is weak, if you boost launch it, the part will eventually break. Their are aftermarket replacements that will stand up to the punishment of boost launches. I would recommend a Gilbert Propshaft. The stock propshaft when it breaks very often takes out other expensive parts, such as the transmission cable, shifter assembly, and breaking the transmission case. If you can not afford a upgraded propshaft, you can alway buy a propshaft loop for $60. $60 is a well worth investment compared to the repair expense that a broken propshaft ussually inflicts; however, it does not fit the Gilbert Propshft.
- Transmission
- The stock transmission is over stressed even with stock engine output. The additional traction of AWD and the torque of the motor exceeds the rating of the 700R4 (also call the 4L60). This is despite the fact that SyTy 700r4 is the strongest and hardest shifting 700R4 that GM made. If you modify the engine it will only get worse. It is highly recommended that you add a transmission cooler. You can also add a deeper pan. If you transmission has high mileage and/or dark fluid I would skip the deeper pan; often with high mileage transmission oil changes the transmission will shortly fail after couple hundred miles. If you do race regularly the transmission will fail eventually, additional cooling will help if longevity. When you do rebuild the transmission make sure they rebuild your transmission. You don't need a shift kit, it will often be softer than stock. I would very highly recommend using a prefered SyTy transmission rebuilder, they can build you a stong transmission that will survive racing. Search on http://www.syty.net for one. For higher HP builds I recommend 4L80E conversions. Warning local rebuilders and recognized name brand catalog rebuilders have a long history of failures behind SyTy engines, despite their claims of sucess with high HP rebuilds. You might save a few dollars, but often this results in multiple tranmission rebuilds. One of the reasons for this is that a low 12 sec SyTy puts about the same amount of stress on the transmission as a Corvette or F-body does running 10's.