[Justins76]

Originally Posted by rfmaster

In 92 305 TBI in Firebird was rated 170HP@4000 RPM and 255 ft-lb/2500 RPM and typically came with very tall 2.73:1 rear end ratio. That combo was the moronic attempt by GM to achieve Corporate Average Fuel Economy (CAFE) to meet fed mandates. Thank you EPA!
The weakest link in a TBI equipped engines is not fuel injection part but a puny camshaft, some what restrictive heads and chocking exhaust system. Stock TBI cam at .050" lift is 179/194 deg (I/E) and maximum lift with 1.5:1 rocker ratio is 0.350/0.384 (I/E). It is outright pathetic, If you stick carb or even TPI on top of a TBI short block (with that cam) you will loose both torque and HP and end up with a bigger dog! I have seen several of these attempts at TBI to carb conversion fail miserably (half had other problems, but this is a family forum so I will keep it clean!)

The key to performance (we are talking solid dd, not a fire breathing monster) TBI is take advantage of what is readily available to any Joe:
mild camshaft (keep it middle of the page: LSA 112deg, lift at about 0.425 to 0.475, duration 195-205deg @ 0.050)
reworked heads (springs, mild port cleanup)
exhaust system (headers, cat after exhaust)
low restriction intake
ECM tuning and optimization.

The key advantage of TBI over TPI is that it is relatively low cost and readily available just about anywhere. I have to admit that I am regular JY visitor and many month go by when before I see a wrecked TPI camaro. Whereas TBI cars or trucks are there all the time.

//RF

Thats true but the LG4 cam was pretty much the same as the TBI cam except that was a roller. From my driving experience I did not get any better mileage with the 1992 TBI over the 1986 carb firebird. If anything the TBI was worse in the city. Both at the time had 2.73 with a 700r4 and both were bought new.

True there is less maintenance and its low cost (not counting my fuel pump in the tank that goes out every 6 years and you have to drop the whole back end to get to the tank lol)