Get under those hoods and work out your fueling issues. At least the Carter design makes tuning changes quite easy.
It's All In The Pod, Man Q What would be involved in replacing my tired old '99 Tahoe's 5.7L Vortec with a Gen I 406 short-block that I've been running in my '72 X-body? I would maintain the 906 Vortec heads on the 406. JohannVia e-mail
A The Vortec L31 5.7L small-block engines are great performers, and the Central Point Injection is very unique on those engines. It uses what is called a Fuel Pod in the center of the manifold. Housing all eight fuel injectors and the fuel pressure regulator, it uses very small nylon lines that run out to the injector check valves at the port of the manifold. There isn't a larger pod assembly that will flow more fuel than the L31 pod. I checked with our friend Tom Woodside at GMCOPO for his thoughts on the fuel flow capacity. Tom says they have built some strong-performing L31-based engines that produced in the 400hp range. This is where you run out of duty cycle on the injectors. The injector pulse width is the period of time when the injectors are open. With a fixed injector size and not being able to swap to larger injectors, you just run out of time for them to be open. The injectors must have a little rest time between intake strokes. Above 400 hp of fuel flow, you have run out of time.
If you keep the engine output to a horsepower per cube, Tom says that the stock air-meter calibration will deliver the additional fuel required by the 406. The stock computer should work well with only minor calibration changes. His next concern would be the transmission calibration, if you are still using the 4L60E that came behind the L31. They can provide the necessary transmission hardware to firm up the shifts behind the 406.
We would jump right in and swap out the tired 350 for the 406 short-block. Watch your compression ratio with the small 64cc chambers and the larger-displacement engine. Also, stick with a short-duration, torque-boosting camshaft; this will give you a great-running truck and will work well with the stock L31 injection. CHP
If you have technical questions for Kevin McClelland, send him an e-mail at chevyhi@primedia.com.