As for headers, you could if you want but at that power level your just going to give yourself headaches with exhaust leaks and burnt plug wires. So I recommend upgrading to dual 2.5″ exhaust. the 1991 454SS that I have does at least have a true dual exhaust setup under it from the factory which is why those trucks made 20 more horsepower than the standard 454 and the 1990 SS trucks. The 2 KEY problems with a 454 engine is GM built it with a terrible low 7.75:1 compression ratio which is not only not good for performance but also causes poor fuel efficiency so if you rebuilding, put some 18cc domed pistons in that motor or better yet a nice 496 stroker kit from Īs with the other TBI and most vehicles in this era, the exhaust is terrible restrictive. fans, pulley, exhaust and a towmaster chip change, I consider the 2nd most important changes to get fuel mileage from your 454 engine and will gain nearly as much as the overdrive. the other things, I recommend for mileage is electric fan conversion which I have a dedicated page for and a underdrive crank pulley to turn those accessories 25% slower and that regained power can go towards turning rubber (tires). Whether you drop in a NV4500 5spd manual transmission or you get a 4L80E with a TCI EZ TCU transmission controller, overdrive is only way to get those rpms low enough for reasonable fuel mileage. Nothing is going to help that fuel mileage more than overdrive. 90 and older is particularly bad and that is largely due to NO OVERDRIVE. Always a big complaint with 454 TBI trucks. Stock TBI 454 makes 230hp and 380tq so stock fuel pump is maxed out right off and a typical 454 will run better with a fuel pump upgrade even with stock chip. So I begin every project with a new upgraded pump. I recommend upgrading to the 1996 Vortec 155lph fuel pump which can support up to 450hp and plugs right into a factory TBI sending unit. However, they can be improved.įirst I start with a new Fuel pump, STOCK 75lph TBI fuel pump will only support about 230hp before the fuel pressure drops like a rock. After messing with my brothers 1992 454 TBI dually truck and now my 1991 TBI 454SS, I am going to say, I am not a big fan of the 91-95 GEN V big block engine.

I have made some changes to this page after learning a lot the hard way of course with my 1991 454SS project truck.

Rv cam for chevy 350 tbi