The 4.3L v6 is a balancing nightmare. Any v6 configuration does not have a neutral balance to it and usually requires a balance shaft to cancel out unwanted harmonics. The 4.3L is an ancient design by todays standards. It did not have the efficiency to compete.

Could it have been redesigned for better efficiency, sure. However, the engine that really replaced it, Vortec 4200 I6 found in the GMT360/370 platform trucks, is all around better.

The I5 in the Colorado was just the I6 with one less cylinder. It makes a lot of sense in that a lot of the design was already done and proven to work. The I5 can be made to put down some pretty good power with work. There are also some running forced induction with great success. The PCMs used in the newer trucks are the restrictive part when making power.

 

of, guestion, why not make more power out of the I5 factory?

 

That is the age old question. How much power should there be? How much reliability should there be? What kind of power can the chassis handle?

Sure, GM could have "turned up the wick" so to say. Original specs on the 3.5L I5:
So compared with the 4.3L, it has more HP, but less torque. The torque aspect should be no suprise when you consider it is doing so with one less cylinder. With a better cam profile to take more advantage of the head flow rates and a better exhaust, you can probably get comparable torque. The push rod v6 configuration will generate the peak torque at a lower RPM than a DOHC 4-valve motor will typically, which further divides the offering.

There is no question that a DOHC motor is more efficient in terms of valve train losses and control. Advances in push rod tech can only go so far. GM is at the fore front of this tech with their LS engines, but it is my opinion that the day will come when they too will switch.

 

on the torque number part, i think if would have been better if the I5 produced more and more at the bottom end.