i dont know much about the older cars, have mostly built crates or FI engines on newer cars. i decided to buy an 82 trans am for the experience of it and doing something new. from wat i hear the 305 block is the exact same as the 350 block other then the heads. if this is true (hoping for some more confirmation) then in theory i can buy heads from a 350 of around the same year and " bolt " them right onto the block.
if i can do this swap and essentially turn a 305 into a 350 wat else will i need to replace other then of course the springs seals etc?
should the manifolds be done? and if so is it worth the effort to make this swap over just buying or building a 350 from scratch?

 

Welcome aboard thirdgen.org.

Your information was either wrong, or misunderstood. Externally, a 305 or 350 (of the same year) would look identical except for the casting numbers. Everything that bolts to the engine would be the same.

The castings for the blocks are different between 305's and 350's. The crankshafts start the same, but are balanced different. The rods are the same. You can't turn a 305 into a 350 in any way, shape, or fashion. The 305 cylinders are 3.736" diameter, and 350 4.000". The most you can increase the bore of either is 0.060", which will leave you well short of 4.000" if you start with a 305.

The heads also start out as different castings. The intake valves of the 305 are 1.84" for 3rd gen 305's, and 1.94" for 3rd gen 350's. Heads for either engine varied over the years, but 3rd gen 305's from 1982 to 1986 got the "416" castings (last 3 digits of the casting number), which were pretty decent heads. The combustion chambers were smaller than 350 heads, 58cc vs. typical 64cc or larger for 350's. Since a lot of 350's came with low compression dished pistons, putting 305 heads on one will raise compression and improve performance.

Most likely your '82 305 is the "LG4" model - the 8th character of your VIN would be the letter "H". If so, it's a low compression, low performance set-up. The exhaust on it is terrible, and will be even worse on a 350. Check the Exhaust forum for what to do about that.

The stock intake manifold, carb, and distributor are fine for a mild 350. The air cleaner is restrictive.

There's a thread on the FAQ forum about differences between 305's and performance improvements. Everything said there about 305's applies to a 350 as well.

 

that pretty much confirms that ill be buying another engine, thanks for the info