Is this really the case? I hear this a lot... but it was in 85 Corvettes with the 350 the same year it was in the 305 Camaros. Did they think they couldnt get away with the 350 in the vette for emissions/mileage reasons and only figured out they could at the last minute?

 

Yes. Because of cafe numbers GM was going to put the 305 in the corvette. When they developed the TPI for the 305 they noticed the horsepower going up and the mpg. Now they could put the 350 on the corvette.

 

Yes TPI was designed for the 305. In the early 80's when TPI was being developed GM was considering not producing the 350 anymore due to new fuel economy and emissions requirements that the govenment had mandated.

GM wanted a way to give a smaller size engine (the 305) the torque of an earlier (late 1970's) carbed 350 while still meeting the CAFE fuel economy standards and tougher emissions regulations.

GM found that the 350 could still continue to be produced while meeting the new govenment standards after completion of a testing program. The problem is that GM didn't want to spend the money to update or change the TPI system for the 350, an engine that is 45 cubic inches larger than the 305. So since the 305 and the 350 were technically still a part of the Gen 1 small block engine family GM didn't want to do a lot of testing and spend a lot of money to get the TPI 350's going and delay turning a profit.

This is part of the reason that most stock LB9's generally pull well to 5,000rpm and the L98's start running out of steam around 4,500rpm. If designed properly GM should have given a better breathing TPI system to the L98 style engines because the TPI system was orginally designed for a 305 engine with 45 less cubic inches, and thus a lower air intake requirement.

Having said that, as I and many others will tell you, there are numerous ways to open up the stock TPI system and really boost the performance. With a modified TPI system that operational range can usually be extened to 5,500rpm - 6,000rpm. There are members on here who have stock style long tube runner TPI systems that still pull up higher in the rpm range. These systems also still exhibit the main characteristic of TPI with respect to excellent low - midrange torque and horsepower that TPI systems are known for.

Back when TPI was being designed it was just cheaper for GM to just change the injectors on the TPI system (305's got 19 pounds per hour injectors & 350's got 22 pound per hour injectors) and the PROM (with respect to LB9/700r4, LB9/5-speed and 350/700r4 powertrain combinations) rather than design a better breathing intake system for the larger engine.

 

That's awesome info, I never know this. I learn something new every day on here

 

I dont understand why they got different injectors? They both could have run fine on same inj whether they were 19's or 22's

 

GM was bent on duty cycle particulars, targeting a certain percentage being used. This is more than likely why the LT1 received 24-lb injectors later on because of the increased velocity from the intake...