Hi; is it feasible to make 300-ish WHP with ~$4,000 in engine modifications with a 305 TBI out of a 91 Camaro reliably or should I look for a moderately used 350 TPI & throw performance parts on that?

 

Feasible, yes. Fiscally advisable, no. Not without nitrous. Or a very deal savvy and capable person in charge of the project. That's 1 hp per ci to the wheels. It's a lot to ask of that smaller ci sbc with so few good head choices and an injection system that isn't performance oriented. You can put the same dollars into a 350 as a 305 and you'll still be down 45ci worth of power. Making a 305 just not worth the value. Sometimes the 350 stuff is cheaper than a 305 based on supply. More 350 stuff out there due to higher demand.
Find a good condition roller cam 350. Tpi, vortec, tbi, short block crate, doesn't matter. Ditch the factory heads. Find good aluminum heads and cam appropriately. Top off with a good intake (carb'd would be cheaper but is losing the advantages efi offers) You'll be at 350 hp to the crank fairly easily, that'll equate to roughly 300 to the wheels depending on your driveline. You've got a decent budget in mind, but you're going to go over that if you're anything like the rest of us. It always costs more, especially in our "lack of supply" world we're currently in. Not to mention that trans, axle and chassis would need attention and money to deal with added power. Good luck.

 

I have a 305 tpi t5 gta
it had got I'm dyno 275hp 375tq engine
and it did 14.30 at 99mph
it smoked posi 1st gear
smoked posi 2nd gear and chirped 3rd gear hard everytime
street tire
I spent 1500 to 2000
Full exhaust
lt1 hot cam
roller rockers
ported cylinder heads
all the free mods
I had the head apart and put stage 1 valve springs
and my engine had 230kms and had horrible low uneven compression
did smoke oil
we thought 300hp and 400tq with a rebuilt engine

 

I had a 305 TPI 5-speed that had around $4k into it and it was quicker than 300hp LT1s. I never dyno’d it’s but it was right there with 300hp cars.

had all the bolt on tricks, smog delete, heads ported and polished, built T5 after it blew two of them, etc...

with that money into a 350 you’ll can get more power though so people will tell you not to bother...

A 300hp car from that era will do mid-high 13s and you can definitely do that with a 305... but then you get stuck there which is why people want to go 350 and even the L98s are limited compared to other options now...

My guess is the TBI would need heads, cam and intake... My guess is also that a carb would be better than the TBI...

 

Single most effective "go fast" part you can throw at a 305, is a BORE KIT for the cylinder block. Amazing how much it accomplishes for how little $$$. BY FAR the biggest bang for the buck mod you can do to a 305. Almost as amazing is, now many people don't "get it", and think that somehow, just because they "have" a 305 and it's "free", they're stuck with it.

 

the below linked engine masters episode suggests 350 (flywheel) horsepower out of a lightly modded 305 is possible. Given the stock 305 TPI topped out at around 230ish (flywheel) there's decent amount on the table there and it sounds like it will meet your goal

 

Achieveable? Yes, but IMO your money would be best spent on a 350, even a 383. You could find a used engine, headers, intake, carb, etc for very cheap. There are SBC parts for sale everywhere. When I pulled my believed 350 and discovered it was a 305, I went LS. But LS is not very budget friendly in the least. Also a TPI swap would be quite a PITA from what I've read. There is no replacement for displacement.