Okay so one of the biggest problems with the 305 is that the cylinder heads are too restricting. So I am planning on putting on new cylinder heads. However I don't really understand what the specs mean. So if someone could explain to me what I should be looking for in the intake runner, combustion chamber and valve sizes that would be great. Right now I am running a 1985 305 H.O. 4bbl.

 

Your HO heads are actually pretty good, for stock heads.

 

Have you already done all the usual bolt-ons? If not, then leave the heads alone for now.

 

I have done exhaust, intake manifold, and am looking at carb for friday. Planning to do camshaft and heads next month

 

I would keep the CCC Qjet if you are thinking of replacing it. It wouldn't even be a bottle neck on the motor until way over anything that 305 can make naturally. They flow over 750cfm (+800cfm easily modified) and you use probably 500cfm at peak now and probably 650cfm if you do a radical build. If you have a real HO then you have a L69 ECM which is the best CCC ECM (think timing control) there is in stock form.

What's your budget for heads?

Personally since you have a standard I would go a bit more wild on the cam then most people would suggest. Nothing extreme, just a bit warmer then a build with an automatic.

 

Like to keep it around the $800 mark, I have $2,000 to spend and I am planning on doing camshaft, beefing up my valve train, and shorty headers as well.

 

If you want to make good power invest in heads. Heads make power everything else on the motor accommodates them.

There are few heads made for 305's bore but there are some that can be made to work. Vortec's and the more uncommon corvette aluminum L98's are two. If you are serious and want to make more power then those invest in Trick Flow Super 23 175cc heads. They come in 3 different flavors depending on your valve train needs.

These are the lowest cost version of those setup for .480 lift http://www.summitracing.com/parts/TFS-30300001/

Those flow enough to make over 400hp if everything else is up to it on the motor. For a 305 to make that kind of power though it's going to have to be more than a bit on the radical side, more then I would do for a daily driver.

This cam would work great with those heads; http://www.summitracing.com/parts/CCA-12-238-2/

it's a comp cams XE262 (.462/.469 lift 218/224@.05") and it would peak at 6000rpm. (very flat from 5500RPM to 6500RPM)

That would leave you about 800$ left for headers, Y-pipe, lifters, pushrods, timing chain, ect.

 

Better to buy the retrofit hydraulic roller lifters and a roller cam to go with the TFS 175 heads, let the easier external mods wait.
A 218/224-112 cam sounds fine, but the lift then is 495/503, and the area under the curve is more than the numbers suggest. It'll be at least 20 horses better than what Doom86 recommended, despite the same duration numbers.
Don't forget the FelPro 1094 head gaskets.