If my friend were to convert his 305TBI to a 850CFM Carbed engine. You think there will be a nice power gain? He's looking to make some nice power out of this engine and I heard that the conversion is a great place to start. When I say nice power, I mean well into the 3's

 

He will probably see a gain, but not a big one, I'd expect around 5-10 HP. The stock heads, camshaft, and exhaust (probably some of the most restrictive parts GM ever produced) are still going to hold it back.

EDIT: Wait, is he swapping in a whole different engine, or just putting a carb on the 305?

 

Carb on a cammed 305 TBI

 

an 850 cfm carb is WAY overkill for a 305.

 

He'll lose power going to an 850 carb on that engine. The carb is way too big, which means no air velocity, which means poor fuel metering. He won't ever be able to get it tuned right, and if he does get it close I expect it'll still tend to stumble/lag badly on initial acceleration. If he HAS to go carb, use a 600 or 650 until the heads are upgraded. Then go bigger, to a 750 or 800 tops. I'd probably stick with the 750.


IMHO there's no sense in swapping to a carb anyway, but that's a whole other can of worms (and likely flames.)

 

Definatly don't bother with a carb, it's not going to help you much.

 

Cam and full exaust will go a long ways. The cams specs on the LO3 are rather sad. A descent cam, some chip work, and full exaust will make a HUGE diffrence. There are several guys running 13's and very low 14's with the LT1 cam, and exaust work.

 

Any stall on that car?

 

an 850 is overkill for a lot of motors.
i would say jsut keep the tbi. the induction system is not the restriction to power that the stock cam is.
check out the free mods on thirdgen.org. they are enough to knock a full second off of the stock 1/4 time
also, get teh car some gears. stock tbi was 2.73's with the auto adn 3.08's with stick. both are factory peg leg, not ideal for performance. throw in a set of 4.10's and it will feel like a whole new car.

later
tim

 

My thoughts exactly.

Unless he plans on putting a very large cam in the car he will be fine with the stock TBI injection.

It is a pretty easy swap to carb though on the TBI cars if it ever comes down to that.