Long-tube Header for Chevrolet Colorado 5-cylinderCOL-401c
The performance improvements on an otherwise stock 2005 extended cab ZQ8 with the 5-cylinder/automatic and 3.42 gears are as follows:
- 0–60 mph, 7.7 seconds (average of three runs)
- 1/4 mile, 15.9 seconds at 89.2 mph (average of three runs)
Modified with JTR/Stealth ram-air intake:
- 0–60 mph, 7.5 seconds (average of three runs)
- 1/4 mile, 15.7 seconds at 90.4 mph (average of three runs)
Modified with JTR/Stealth ram-air intake and header:
- 0–60 mph, 7.2 seconds (average of three runs)
- 1/4 mile, 15.4 seconds at 91.6 mph (average of three runs)
All measurements were made with a Vericom 2000 accelerometer/performance computer.
All of the above tests were done with the outside air temperature at 45 to 50 degrees F, which helps explain why the 1/4 mile performance and 0-60 mph times are better than most other published information.
The outside air temperature has a very noticeable difference in the 1/4 mile performance — this is, in part, due to the high compression ratio of the stock engine.
When the truck was tested in 70-degree weather, the quarter mile times were lower by about .4 seconds, the trap speeds were slower by about 2 mph, and the 0-60 times were about 0.5 seconds slower. This also provides proof of the performance benefits of a cold-air intake.
All tests were done with a full tank of 87 octane gasoline.
Using a formula to calculate horsepower based on 1/4 mile performance, the header adds about 10 hp. The header and ram-air combined adds about 20 hp.
The header is not smog-legal and is for racing and off-road use only.
HEADER INSTALLATION INSTRUCTIONS
The basic installation will probably take three to four hours plus a trip to the muffler shop.
A muffler shop should be able to connect the header to the exhaust in less than an hour.
HEATER HOSE MODIFICATIONS
Remove the stock exhaust manifold. This requires removing the air cleaner assembly, and the intake ducting going to the engine.
The heater hoses will have to be disconnected and shortened by cutting a few inches from the upper sections that connect to the firewall fittings.
Before disconnecting the hoses, drain about 1 quart from the cooling system.
Disconnect the heater hoses from the firewall fittings as shown above by squeezing the plastic connectors and gently pulling the hoses from the firewall fittings. This should be done to avoid damaging the heater core when shortening the hoses.
Remove the heater hoses from the plastic fittings. Cut the hoses so that an inch of straight section can be used to connect the hoses back onto the plastic fittings. Reinstall the heater hoses as shown below.
The header is installed from the top of the engine compartment. It is a tight fit and requires some careful maneuvering to get the collector between the engine and the frame rails. See below.
Use the stock metal gasket between the header and the cylinder head. Also use the stock bolts.
Check for clearance between the frame and the header tubes. The clearance between the fame and the header is very tight. In some cases the header tube will be too close to the frame (less than 1/2 "). If so, mark that section of the header tube, remove from the truck, and use a small hammer to flatten the header tube as needed.
Install the transmission dipstick tube between the 3 and 4 header tubes. The bracket that bolts to the cylinder header will have to be bent.
OXYGEN SENSOR AND EXHAUST HOOKUP
The oxygen sensor is installed at the collector as shown above. The wires need to be extended about 2-1/2 feet.
Connecting the header to the exhaust normally requires a trip to a muffler shop. The header can be connected to the catalytic converter as shown by using a 3" to 2-1/2" reducer at the header and having a muffler shop fabricate a 2-1/2" diameter headpipe to connect between the reducer and the catalytic converter.
For best sealing, use a copper gasket.
CHECK ENGINE LIGHT
If the truck is started without connecting the Oxygen sensor, the "Check Engine Light" will come on. The "Check Engine Light" will not turn off by disconnecting the battery.
To turn the "Check Engine Light" off, a scanner designed for OBD2 diagnostics is required. The scanner plugs into the diagnostics port located under the dash, near the hood latch release lever.
Scanners, similar to the unit shown above can be purchased for less than $100 from most auto parts stores.
After first installing the header, your engine will probably surge during acceleration.
The engine computer needs to re-adjust itself due to the improved exhaust scavenging provided by the header. Normally, the engine computer will "learn" by itself using a term called "block learning." The surging will go away within a few hours of driving, but it can take several days for the computer to completely compensate for the header under all driving situations.
To make the computer learn faster, disconnect the battery for one minute. This will erase the previous "block learning." The engine will still surge for a short time, but it will normally go away within 1/2 hour of driving.
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