Small Block & Big Block Chevy Specific - olds 403 questions..

im looking into getting a '79 trans am...its got a 403 ci motor in it..im wanting to do a fuel injection conversion on it.. it will have a built 9' with 3.90 gears and a 700r4 tranny with around a 3800 stall...would it be worth it to do the conversion or would i even notice the millage difference??

the quadrajet is a great carb, my bro is going to put a 403 in his 83 hurst olds, if you need any info on the motor, pm me, i will ask him.

cool thanks...im mainly wanting to know what kind of gas millage i would get with the conversion?? cause if its not much better im going to do a lsx / t56 swap into it...but if i could get around the same millage with that set up then i couldn't justify spending all that money on an lsx swap...

I think you would be money and power ahead to do an LSX swap. Fuel injection is expensive and on a 403, you might get 17-18 with a FI 700R4 set up. LSX/T56 dumdumdum!!!

yea...that was my original plan...but i didn't want to have to wait for that...is there any shops that does it?? the whole swap (motor, wiring, t56, ect...)???

The ls swap costs a lot of money, it is all of the extra stuff that nickels and dimes you, a friend just swapped an ls into a 90 firebird and spent 10,000 on everything and he did it himself. There are shops that will do it, but it will cost alot of money. My bro is building a 403 right now, the problem with it is the thin walls..no nitrous or forced induction, and once you rebuild it once or twice the block does not have enough material to machine it again. He claims he will see around 400 hp, and some crazy torque, but I will wait and see.

Ah, the old down-sized Olds big block- externally similar to the 455- and a real torque-monster. I had one years ago, in a 98- too heavy to be quick, but you could fry the tires any time, any where-

A lot of work to switch over to an LSX car- the cheapest way would be to find a crashed donor car, because you will need all sorts of sensors, harnesses, computers, etc. etc- not a trivial job- if the old Firebird is in good shape, it might be worth more to keep stock, and collectible-

yea i deffinatly think that keeping the stock 403 is out of the question, mainly for power/ fuel millage....im lookin for a 11 sec daily driver..and the money is not that big of an issue as long as it gets done right...it will probly be a project spread out over a year or 2 to get where i want it...thanks for all the suggestions...

You will be happier with an LSx swap and it's not really that hard. Also you don't need the 9" unless you plan on making some serious power.