Hi,

My sister wants some work done on her 91' 305 TBI to bump up the power on it a little. What is a reasonable hp expectation out of a TBI 305 engine with minor mods done to it.
ie. headers, different air filter, exhaust possible even a cam somwhere down the road.
Is it better to save up and go for a switch to TPI or a complete 350 swap. I don't personally have a whole lot of experince with the TBI 305 engine. How many mains does it have, what types of internals did they come stock with?


Thanks for any info

 

better off just leaving it alone unless you put nitrous on it like me (check the sign)

just simple bolt ons such as headers and crap won't hardly do anything

all GM 305s are 2 bolt main blocks if someone tells ya they have a 4 bolt main 305 just smack em

as far as the LO3 is concerned from the factor the whole motor was not built for performance it was built so that people that couldnt afford a TPI car or didn't want a gas hog could have a V8 the heads,cam and injection setup are junk. it was made for gas milege not the 1/4 mile thats why Mustangs beat LG4 (carb 305) and the L03(TBI 305) its only got 170 hp stock and with just bolt ons you might end up with 200 not worth it but it can be done just spray it with some help from the N.O.S company

 

Bull****, headers are probably the biggest mod you can do to an L03 as far as bolt on's go. You can expect a huge increase in power with them. As far as bolt on's go, you can probably expect around 200 or so hp, and with a bigger cam you can possibly approach 250 hp if done right. If you really want to make power though, you will have to ditch the swirl port heads. Don't let anyone tell you the L03 can't be made to perform.

 

An L03 with a cam, heads, intake, etc isn't really an L03 anymore. I think what you meant was, don't let anyone say a 305 can't be made to perform - but when you get done "making it fast," all it will have in common with an L03 is the displacement and firing order...

I think what you really meant, though, is that the small block Chevy has great performance potential, something we all knew. And if you wanna pat yourself on the back for owning one, well, feel free, I guess.

 

Hey,

I've messed around with 350's in my truck and the LS1 in my TA. Are you guys basicly saying that the 305 in general will respond similarly to mods like these engines. Are the swirl port heads that were mentioned pretty low flow small valve heads? Is there a site out there that has info on the L03 engine? Things like what type of lifters, compression ratios and valve sizes.
One more thing, how big of a problem is it with the 305 having only a two bolt main. Doesn't that tend to make for a weak bottom end if you start dramatically raising the horsepower?

 

2-bolt main block will hold up just fine with room to spare to any horsepower you're going to make with a NA 305. As for responding to mods similarly to the 350's you mentioned, a 305 will not respond as well to the same mods, the same mod on a 350 will have a bigger impact on power than on a 305. The 305 has one inherent flaw that will always limit it to reaching power like a 350 and that's the fact that it has a small bore as compared to the 350's 4" bore, there's no way around that. You need to decide exactly what kind of horsepower numbers you're looking for and then we can give you advice as to what the best route would be.

 

The L03 is also known as the 305 tbi which got a bad rap because it has a very small cam and very low flowing heads. For that reason tbi has a bad name because it was put onto such a lame engine. What I was saying is that the 305 tbi can and has been made into a very nice performance engine.

 

I agree, with a new cam and heads, along with your normal bolt-ons, these cars can be easily as fast as the last of the LT1 Z-28's and Impalas. As for ever reaching LS1 speed, I highly doubt it, unless you're on the juice.

Then again, since it's a girl driving the car, her definition of fast might be easily more obtainable (ie exhaust and gears).

-The Gunny

 

your hanging out with the wrong girls

 

****, just start out with a flat bottom 14x3 open element

 

Put a good exhaust on it.
Although the performance gains may be minimal, the sound should keep your girlfriend happy How cool is it for a chick to drive around in a Camaro with a good exhaust note.
(At least it worked for my wife ;-) )

Look at my sig to see what I've done to my L03. It made alot of differnce (I leave stock 305 TBI and TPI's in the dust), but it still sucks so I'm ditching the 305 for one of the 350's in my garage (probably the 4-bolt main block)

 

Dude, the best to do to that car is to open up the exhaust. Get a 3 inch exhaust and a set of hedders. You will notice a very good gain from just that. Simple bolt ons is about the best way you could go.

 

your GF needs one of these.....

 

hey,

Yeh, its my sisters car not my girl friend, minor difference. As to the super charger my TransAm needs that before the camaro........ The LS1 would be making 400+ with one of those babys on it

 

This guy doesn't have a clue other than he's right about the amount of HP from bolts-ons. His stock car with nitrous is probably slower than my LO3 NA.

With just bolt-ons (headers, exhaust, K&N, timing, and gears) My car made 178 rwhp (~205hp) and 271 rwtq (~310tq) and That's ~35 more hp and 55 more ft*lbs than stock. At this power my car ran 14.7s @92-93 mph.

However, this also knocked more than a SECOND off my 1/4 mile time (documented). Probably closer to 1.7 secs, but I never ran the car completely stock w/o the gears.

Here's my list of what bolt-ons did for my car.
mods vs 1/4 times

I'd say the stock heads limit the power to ~250 hp. A NA 305 done right could stay streetable and make close to 300 hp.

One thing to keep in mind is that if you change the cam, then the you HAVE to get a custom chip for it to run well.

 

heres a hint


NNNNIIIITTTTRRRROOOOUUUUSSSS

or to the ricers ..........NNAAWWSSS