Now with all these limitations, you can still build a performance 305 that could make 330 hp, but consider that this same combination would make at least 50 additional horsepower because of better breathing with the larger bore. These are all reasons why you don't hear guys putting a lot of money into a 305-because it doesn't pay off the same as it would with a 350 or 383 combination. In one of the other letters in this column we outline the parts necessary to build a relatively mild 383 that would make far more power than the 305 without spending a bunch more cash. If we were to build both engines side by side with the same parts, the 383 would make a bunch more torque, which is a great advantage on the street. The only real advantage the 305 offers is that you already have the engine. To rebuild it will cost the same as rebuilding a 350 and only slightly more for a 383 with a stroker crank. When the crank is only another $229, it's hard to argue against something that inexpensive. If you can't afford a stroker crank for under $300, you probably shouldn't consider building an engine anyway. There are even some 305 stroker kits floating around, but don't get sucked into that, because again, you're still working with a tiny bore.
Having dumped all that on you, let's say you still want to go ahead with a 305. The best move would be a set of decent cylinder heads. The best iron head with a 1.94/1.50-inch valve assembly is the Vortec. With its 64cc chamber, it will still deliver a 9.1:1 compression ratio with a flat-top piston with a 0.030-over bore, 0.042-inch-thick head gasket, and a deck height of 0.010 inch. Because this is a tiny engine with decent heads, there's no sense in trying to make a ton of horsepower. We'd suggest a relatively mild hydraulic flat-tappet cam such as a Crane PowerMax H-278 with 222/234 degrees at 0.050-inch tappet lift and 0.467/0.494-inch lift. With this much valve lift, you will need to make some modifications to the heads to allow additional lift since the heads are limited to around 0.450 inch. You can buy Vortec heads from Scoggin-Dickey (or several other mail-order GM Performance Parts dealers) that have already performed these modifications for you. The heads will cost a little less than $1,000 for the pair. Match this up with a good dual-plane intake manifold like an Edelbrock Performer RPM Vortec (PN 7116, $181.95 from summitracing.com) or a Weiand Air Strike Vortec (PN 8502, $209.95 from summitracing.com). Combine that with a 600-cfm vacuum-secondary carburetor, a set of 151/48-inch headers, and a 211/42-inch exhaust and you're looking at roughly 320 hp. Plug these same parts into a 355ci small-block and you're looking at around 375 hp.
CC Quickies
Chevy Orange
Did you know that the lid from a rattle can of Chevy Orange is the perfect size to seal up the tailhousing on a 4L80-E? We plopped one on right before we yanked this four-speed from a project car and never spilled a drop of the red, stinky tranny soup.>
As for your question about the 302, both the Chevy and Ford 302 offer the same 4.00-inch bore and 3.00-inch stroke combination. The reason these engines make decent power is the larger bore. They don't make as much torque because, like the 305, displacement is limited. But they do make great horsepower because you can rev them. The 305 can be built to spin, but that longer stroke tends to add piston friction and it's not nearly as efficient at higher engine speeds. Engine builders who want to rpm an engine choose a big-bore-short-stroke combination. That's why all the current Pro Mod drag race engine builders are going to these wider-bore-center custom blocks and heads, which makes filling the cylinder easier.