TBi to carb?

[jhicks]

Im currently running a terrible 4.3 (non-vortec) in my 94. Its a manual 5 speed btw.

I want to swap from the TBI 4.3 to the Carbed 350. I have a 350 that has been bored .30 over with a 283 cam, Edlebrock Performer X intake and a double roller timing chain. i want to put it in my truck but i want to have some kind of economy.

Im currently only getting around the 15 mpg range anyway in the 4.3, I want to take the cam out and replace it with a stock cam. So with the stock cam and the other mods, could i keep at least 15 mpgs? Im fairly new to the Chevy truck scene. I just recently got out of Hondas. any help would be appreciated.

 

[TylerZ281500]

explain the second paragraph? your 4.3L is cammed and you want to put the stock cam in yet you want to swap to a carbd 350?

or are we talking you want to take the cam out of the 350? whats the lift and everything on the current 350 cam, stock tbi cams are beyond crappy so are the heads and intake. stockwise that is. what heads are on the carbd engine?

theres many swaps to swap to carb but basically you need to adjust thottle cable, modify wiring harness(zip tie stuff out of the way) and youll need a fuel pressure regulator. now that is basic of the basic but do a search for some other threads and you can see what others have done.

15mpg on a 350 is probably not possible with city driving. a vortec 350 might, i dont see a carbd or tbi one doing it though. im no heavy foot and i only get 12-13.5 on a good day.

 

[jhicks]

im currently running a stock 4.3

i want to swap to the semi-built 350. just to remove the after-market cam so i have a chance to redeem some mpg.

i have no clue what the lift is on the cam.

and as far as i know the heads are stock.

 

[4x4incountryboy]

its like anything, if you get the carb tuned in right it actually has potential to be better than a tbi because its mechanical and doesnt rely on all these electronics

 

[TylerZ281500]

countryboy is right. just dont go back to a stock cam thatd be a bad idea.

 

[jhicks]

why would it be a bad idea? i figure it would bring my economy up alittle.

 

[4x4incountryboy]

depending how worked your engine is, you wont see much mpg gains at all...none justifyable to go out and buy new to replace whats already in the engine like seals, new crank, ect. If the engine is already "built" the carb is probably already adjusted for optimum or close to it performance. Not to be rude but if your worried about the little mpg you will see by downgrading an engine that already gets poor mpg then you should look into another vehicle. you would be better off doing things like headers, a full exhaust system, better air filter, and few other small mods if your looking for mpg gains as well as hp

 

[TylerZ281500]

Agreed. Im blunt terms stick tbi everything literally chokes an engine. Im getting better mpgs with my built 355 tbi than it was stock with more power and everything. My 383 tbi got 13-14 city with it incorrectly tuned. There's alot more work in tuning a carb but the engine internals are better than anything stock tbi. With a bigger cam depending on cam the engine will breathe where its suppose to instead of having a cam that's too small for even your 4.3

 

[4x4incountryboy]

not to mention, opening up the engines lower half and swapping bearings, cranks, and seals gives greater potential for failure if there is contaminents, a bearing isnt seated right, there is too much "play" with the cam, and so on....In college, we built diesel motors had to give precision measurments using micrometers and such determine wear, replace, and rebuild things....lets just say mine was one of few that didnt blow....anything from bearings being in wrong to bolts being torqued wrong resulted in holes in blocks and everything else...I dont mean to scare, but when it comes to something that you can easily spend hundreds if not thousands to replace because of a mistake, its best to know what you are doing.

 

[jhicks]

I guess this would be a fine time to state that the motor is being rebuilt before it even gets close to my truck. And it doesn't currently have a carb on it or dist. I don't do the whole "used motor thing" I may be new to 350 but I'm not new to motors.