Is the 454 TBI's intake manifold an upgrade over a stock LO3 intake manifold? Would the 454 TBI be too much for my engine with the little mods?(see sig). I am able to get a 454 TBI intake manifold and TBI. I was thinking of swapping my injectors. Do you think this would work and be worthwhile?

no. won't fit.

uh, big blocks have well, bigger blocks. a 454 manifold will not fit on a small block.

and your engine is stock. you will cause more headaches than horsepower if you put a 454 tbi on a stock 305

The 454 tbi will fit the small block engine. You don't use the big block manifold it won't fit. The stock small block tbi manifold can be bored out to 2" to fit the early 454 tbi, but don't try to go to
2 1/16". The early 454 tbi is a direct bolt on to the small block tbi manifold. If you go with the big block tbi, you may need to make a spacer to go between the manifold and tbi unit to provide a sort of plenum for more airflow. If you can get it past a smog check, a high performance 4 barrel manifold with a plenum might work even better with the 454 tbi.

again, dont put the 454 tbi on a 305 making under 280 hp and you cant get a custom eprom. its not needed and will cause you to go lean on acceleration because your pumpshot will be off. You will be bringing more air into the engine than the computer thinks is coming and and you will get knock. Your ecm will then retard your timing, and you will LOOSE power. Off idle acceleraion definately suffers and feels like nasty turbo lag.....

ive done it, dont do it.

russ. plenum = spacer? um no. your terms are confusing.

you would need a spacer so that the bbtb butterflies clear the manifold.

again, dont bother. spend your money on other things first, then later maybe get the larger throttle body.

Kevin91z's dad put a 454 tbi unit on a bored out tbi manifold on a 383 in a early 80's El Camino. It originally had a Holley carb and Edelbrock Performer manifold, the guy was getting under 10 mpg. The tbi ran much stronger through the rev range than the Holley (it might have lost a little top end) and got much better fuel mileage. I think Don and Kevin had to burn a custom chip to get it right, though. I don't know how it would work on a 305. The stock tbi is probably plenty big for a 305. When the question was asked about the 454 tbi, I didn't realize he was talking about a stock 305.