I have a 89 firebird formula. It has a 305 throttle body injection. Does anyone know if it is a 2 or 4 bolt main. And if i get a 350 4 bolt main will there be any trouble putting it in. Also i have heard if im switching to carburator do i have to get a different fuel pump?

 

I just went from injection to carb and I did not change the pump. You just have to run a return style regulator like a mallory 4309 (i think that is the p/n). There is a tech article on this site for switching from injection to carb.

I think all 305's are 2 bolt but I am not sure, but it doesn't matter. I went from a 2 bolt main to a 4 bolt and the main bolts are internal and there is no difference externally. If you are keeping the same type of trans I would just say to get a flexplate or flywheel that is a 158 tooth so your old starter will work.

The other piece on advice is that is you are going to build a 350 you might as well make a 383 since the difference in build money is very small.

 

There's almost no reason to care if it has 2 bolt or 4 bolt mains.

 

153 tooth, actually.

There's at least $500 difference. A lot more if you do it right.

firebirdman, the most important factor is the "era" of the engine. Is it '68-'79, '80-'85, or '86-later? Not that these are "big" differences, just details. As stated, 2- or 4-bolt main is irrelevant.

 

500 if he has it built or if he does the work himself? I mean he will have to have the bores done most likely anyway on any gen I 350 he finds and the rotating assembly prices are not that far apart are they? Like 150 - 200 bucks for the hyper systems? But I guess he could re-use parts like the flex plate and balancer if he went 350.

I guess the amount of small or large is relative. Even 300 to 400 bucks on I build that could run several thousand could be small diff to some and a larger diff to others.

153 tooth! Damn, my fault on that one I guess I combined the 2 flexplates. the other is a 168, right?

 

A 350 that already runs is cheaper than rebuilding a 383. It's only when you're rebuilding them both that they cost the same.

 

I guess I just assumed he was building but I guess he may not be.

 

$500 for parts over a 350 rebuild.

The two flexplate/flywheel tooth counts are 153 and 168.