If you are not a strong mechanic what can you do to enhance the performance of your 305 engine in a 1979 Chevy Nova?
No the first and most important thing you can do is replace the cam and heads. Everything else is junk. get competition headers from hooker since they are just about the only headers you will find for that car. Then just get some Jegs aluminum heads and a cam with .45 lift max unless you want to get really into it and a cam with a duration of 201 intake and 204 exhaust 105.3 lobe center angle and 105.5 intake centerline. Then get a 390 to 450 cfm Holley carb unless you have one tuned for a 305 and I suggest Holey because they are 10 times better than any universal carb you can find. Dual plane manifolds are highly overrated I suggest a Torker 2 manifold it work great I have it on my 76 nova 305. Your compression ratio will likely drop with the new heads because most smog 305s have dish pistons meaning you have small combustion chambers, which is why a set of 350 heads meant for flat top pistons don't work. Also get MSD it'll be about $500 for the whole setup but its worth it. Go to Summit racing for the cam because you can order a custom grind cam from them with lifters and all for really cheap. But make sure your tranny can handle this because 4th gen novas like that come with the THM-250 instead of the THM-350 for weight savings if you have to get a street-fighter transmission and components from TCI it'll be about $1000 for the whole tranny setup with torque converter. Keep stock gears unless you want your highway driving to suffer. If you want disc brakes in the rear get a second gen camaro or firebird/trans-am with disc brakes and posi. Now you need to get wider tires then those 215s you have and swap out for some 245s or 255s.
If you have the stock Q jet- you are limited. If you have an aftermarket carb, your power potential is greater.
-1.6 rockers- makes the engine *think* it has a bigger cam. I use and recommend aluminum roller rockers.
-Headers- no larger than 1 3/4, 1 1/2 will make the best torque.
-New free flowing exhaust- 3" if you are running a Y pipe, 2.5" if you are running duals. Good mufflers (I prefer Flowmaster for sound).
-New intake manifold (Edlebrock Performer/ Performer RPM).
-New carb- your choice of brand, no larger than 625 CFM.
-Add an electric fan- get rid of the clutch/water pump driven fan.
-New gears (make you 'scoot' quicker).
-Remove your emissions junk if you can- it's ugly and heavy. Did I mention it's ugly?
If you really want to get down and dirty, get a new cam and 416 heads- 416 heads have 58cc combustion chambers, and will probably increase your CR. Never use 350 heads on a 305- it will only cause problems. If going with a new cam, ALWAYS use new valve springs and hardware. I'd recommend a cam with around 212-218* duration at .050 on the intake side.
keep in mind that a 305 has a small bore size and a "good set of cylinder heads" will not work because of engine block interference with larger valves. It is difficult to make allot of power because of this problem. A 305 shares a crank shaft with the 350 ci. It has a much smaller bore size to reduce the engine size. Its not a good design. It was done to increase fuel mileage in the 80s. Kind of a band aid fix. If you like the small ci Chevys use a 327, 302, these are high revving engines with a 4" bore and have allot of potential for power gains