I have a tired 305 tbi in an '89 firebird and will be looking to replace it soon. I want to stay with a small block and, if at all possible, the tbi setup for a temporary basis. the tbi thing is just to make things easy in the emissions arena and stay within a budget. I really would like to put in a 400 sb, but i'm not sure if I can use a tbi manifold on the earlier block. do the heads make a difference in the way a stock-stylet intake manifold would bolt on? just curious. im also open to other ideas on what motor to use.

thanks

 

It can be done.You will either need 350 injectors,or a 454 tbi unit with 454 injectors.chip burning,new heads because 400's suck and they will need steam holes drilled in the heads.The intake can be used by drilling the holes in the right angle,or use an old carb intake and useing an tbi adapter to the intake.You will also need a new flywheel/flex plate if you are useing the same transmission.These are the basics,and others might chine in.You can also do a search.Also a late model 350 would be a direct bolt in and a lot easier.You can use the tbi intake and heads with no problem and nothing to change on the flywheel/flexplate.You can also you your tbi,but moveup to 350 injectors.

 

If you drop in a 400 you will need a new flywheel (external balance) and a starter becuase it wont swap been there done that

 

The TBI intake is made for '87 and up heads. The 400 block will accept the '87 heads. Your 305 has a onepiece rear main seal, so your oilpan won't fit the two piece 400 block. you need a 86 or earlier f-body pan. You can use a 86 and earlier 153 tooth flexplate or flywheel and a bolt on balancing plate for $12 . And your old starter.

 

thanks for the info

 

also, about how much power could i expect from a 400 w/ a good rebuild, good injectors, a good computer tune, headers, and maybe even a true dual 2.5 inch exhaust?

 

I don't know but you should start spending your time reading posts in the TBI forum. BMmonteSS just started a workshop for tuning there. You may not know it but TGO is one of the best places on the web for information on GM TBI. Maybe the best. Tuning is the key to TBI and if you want the most out of your combination you got to learn this stuff and do it yourself.

 

The TBI heads wont have the cooling holes for the 400. You could just use the heads on the 400 and redrill the intake. The middle intake bolts are angled diffrent in the centerbolt heads so you will have to redrill them so he bolts can go into the 400 heads.