They have different heads, the bolt pattern changed on two bolts in 87 or 88 I think. But if you've got LB9 heads from 90 and L98 heads from 90 they're interchangeable with obvious affects on performance.

 

so 350 chevy heads wont bolt up to a 305 at all?

 

Yes, 350 heads and 305 heads are interchangable on either engine. However, a 350 head on a 305 will cause a servere drop in compression, which in turn may cause a loss of power.

The 305 heads had 58cc combustion chambers, the 350 heads had (I believe) 64cc chambers.

 

Generally you dont see a drop in power but the gain is nowhere near what people expect because of the very reason you listed. Switching to a different gasket can help bump that compression up just a little more.

 

K so if i wanted to put some 350 vortech heads on my 305 TPI i could do this? OR i would have to use normal 350 heads? Also, why is it that the motor just doesnt have as much horspower as a 350? The 3.74 bore im assuming.

 

Wouldn't putting 350 heads on a 305 compound the 305's valve shrouding problem since the valves on the 350 are bigger?

 

definately, that is a issue

 

Yeah but the bore is still just really small. We are working on saving for an SLP Exaust for my buddies setup right now. Ill let u know his mods, how it goes, money spent, and what he runs. He wants alot of power but still pass smog so ive turned him onto a vortech supercharger. Which makes 325 hp on a 305 bone stock.

 

I had one for two years, actually its laying in the garage and I'm thinking of putting it back on.
I was able to hang with a mostly stock ls1 (gears and exhaust)
...until i had to shift (damn i'm just too slow shifting)

 

Damn thats insane, well my buddy wants his to be that fast and even more, i hope it turns out well.

 

Make sure you get a SQ, those are the quieter ones. Mines just too loud

 

indeed :]