GMC SyTy Reliability Mods

Syclone/Typhoon's came from the factory with relatively weak pistons and rods. An untuned or improperly modified Syclone/Typhoon engine commonly detonates or pings which will lead to undesired result, usually this is a cracked or melted piston, broken piston ring or connecting rod through the side of the engine block. For any new owner, I would highly recommend all of the upgrades below before any wide open throttle driving with a Syclone or Typhoon, at the very least make sure the scan tool is running clean. Don't make the mistake of assuming your truck seems to run good, because it feels strong or your truck has low mileage, it will often be an expensive mistake.  

The Basic SyTy Engine Tune Up:

• Scan Tool
• I would highly recommend a Scan Tool software, such as Datamaster or Tuner Pro. You will also need a Laptop and ALDL cable to run the software. Detonation is the number one killer of SyTy engine and the timing (spark/knock retard) the ECM pulls greatly reduces your engines performance. This post is a good source for reading a scan tool. Don't be discourage if your new Syclone or Typhoon doesn't run clean on a scan tool, a large majority of them do not.
• Vacuum/Boost Lines
• I recommend replacing all the boost/vacuum lines on all but the ultra low mileage examples of SyTy's. The vacuum/boost lines that are very important are the turbo solenoid/boost control & the fuel pressure/MAP sensor harness. A leak in the boost solenoid harness will result in overboost, a leak in the map/fuel pressure harness will result in lean condition. Here is a diagram of factory vacuum lines. (they will also be on the factory fan shroud) The can be recreated with 4 & 6mm hoses, preferably silicon. Any lines that are under boost, need to be zipped tied. The factory hose used metal clips for any hose under boost.
• Spark Plugs
• These trucks are finicky in terms on ignition, ignition problems often show up as tachometer flutter. I would recommend change the plugs at least every 12,000 miles, I do mine every oil change. Most owners have had success using AC Delco CR42TS, NGK UR5, UR6, UR5ix, or UR6ix. The NGK '6' plugs are one heat range colder than stock, which helps with knock retard. The trade off with colder plugs is they tend not to last as long. Gapped them at 0.032-0.035, The NGK 'ix' Iridium plugs can't be gapped.
• Spark Plugs Wires
• Use quality 8mm spark plugs wires such Taylor Spiral Pro's or 8.5mm MSD. You can use the original clips if they are still on your truck. Make sure to route and tie up the wire so they are not resting on the exhaust manifolds or down pipe.
• Cap and Rotor
• It is highly recommended to use a brass cap and rotor. I would replace the cap and rotor on the same schedule as the spark plugs. Autozone & NAPA sell the brass cap & rotor.
• Walbro 255 Fuel Pump
• The stock fuel pump is barely adequate for a stock engine, as it ages its capacity is reduced. I recommend this for all trucks even ultra low mileage ones. You may need to upgrade to a slight higher amp fuse for the fuel pump.
• Adjustable Fuel Pressure Regulator
• You will need to add a AFPR with the Walbro to adjust the FP. The stock Fuel Pressure is 42 psi with the vacuum line disconnected at idle. Most of the stock injector 3 bar aftermarket chips use 45-50psi.
• Intercooler Pump
• To check IC operation, short (paper clip) the A & B terminals on the ALDL with the key on. You will be able to hear the IAC ticking nerar the throttle body and the Intercooler pump near the front bumber cover, if its still working. Most likely the stock IC pump won't work. This result in high intake air temperatures. Aftermarket ones to use are Jabsco, Johnson, or Shurflo Intercooler Pumps.
• Timing
• Timing should be set to 0 degrees initial timing with the tan (w/ black stripe) ESC wire under the dash disconnected. The ESC Electronic Spark Timing Wire is under the carpet on the passenger side below the heater box. It is disconnected to set the timing, then reconnected. The balancer sometimes spins, so it highly recommended to do a TDC check. This is good thread for loosening to the Distributor Bolt and for checking TDC.
• Fuel Filter
• When replacing the filter use flare nut wrench so you don't mess up the fuel lines.
• PCV Valves
• It is important to use the correct PCV valve, the AC Delco part number is 799C, The PCV valve will be stamped with an 'E' on the bottom.