350

[adam89]

i wanna do away with the tbi and go carb what would be the best way to do this im also gonna BEEF up the engine ,im gonna stay with my tranny 700r what do yall think

 

[Jims86]

i wanna do away with the tbi and go carb what would be the best way to do this im also gonna BEEF up the engine ,im gonna stay with my tranny 700r what do yall think

Whats your reason for switching to Carb? Its a step backwards.

 

[lusktommy]

i wanna do away with the tbi and go carb what would be the best way to do this im also gonna BEEF up the engine ,im gonna stay with my tranny 700r what do yall think

ok well you have LT heads so your gonna have to modify an aftermarket carb intake or buy one all read modified, its your choice on the intake. now a 350 came factory when it came with a carb was a 750CFM rochester 4 barrel and they are awesome carbs personally i love them. but on a 350 your secondaries will never reach 100% open, hint why rochesters gum up easily. so i would get a holly street avenger 670CFM carb they have awesome response and performance with out draining your wallet. now i would also trash the original cam and put a very mild cam in it like an RV i can give you the durations of good cams to run if you want. but you have to keep in mind your drivetrain isnt beefed up to handle extra horsepower main worry is the TH700R4 that will not stand to much over stock horsepower with out beefing it up as well. trust me ive shelled 2 haha. and you can also keep the stock distributor and just add a good higher output HEI coil on it and a good performance set of wires. i have a beastly 350 that i build from the bare block up will all new internals and high dollar **** too. you can run into money quick but you need to stick with a mild performance upgrade unless you wanna beef the 700R up then we can talk more about raw horsepower haha and mine isnt mild its got alot of pep it'll make my posi 3.08 boil the rear tires haha that what i shelled 2 700R transmissions im going back with TH350 short shaft

 

[Jims86]

LT Heads? where do you get your info?
He has TBI swirl port 193 heads. Not good for high performance, but good for low end torque and fuel economy. The best bang for your buck would be a set of vortech heads, and an LT4 cam. You will need a specific manifold for the Vortec bolt pattern. A 750 cfm carb, either qjet or holly, would be a good choice.
As far as fuel system, you can still use the in tank electric pump, but you will need an external regulator that will drop the fuel pressure to around 7 PSI.

 

[lusktommy]

LT Heads? where do you get your info?
He has TBI swirl port 193 heads. Not good for high performance, but good for low end torque and fuel economy. The best bang for your buck would be a set of vortech heads, and an LT4 cam. You will need a specific manifold for the Vortec bolt pattern. A 750 cfm carb, either qjet or holly, would be a good choice.
As far as fuel system, you can still use the in tank electric pump, but you will need an external regulator that will drop the fuel pressure to around 7 PSI.

i have always referred to those heads as LT heads because of the center bolt cover pattern and the center intake manifold bolts are different angles and i was thinking about Vortec heads too so....my bad lol i see now what they are really called thanks for the correction. but he is running stock 700R which he doesnt need to much performance or he might run into trans failure later so the 193 heads would be all he would need and i would think a 750 will hurt him on fuel economy is why i recommended a 670 holly avenger or even a 600CFM universal holly would be better for fuel economy and still deliver performance with it really depends on what kinda performance he is wanting..i was recommending things to give like 75 to 100 horses over stock. mild performance gain.

 

[Old77]

wow

You must be registered for see images attach

 

[Jims86]

i have always referred to those heads as LT heads because of the center bolt cover pattern and the center intake manifold bolts are different angles and i was thinking about Vortec heads too so....my bad lol i see now what they are really called thanks for the correction. but he is running stock 700R which he doesnt need to much performance or he might run into trans failure later so the 193 heads would be all he would need and i would think a 750 will hurt him on fuel economy is why i recommended a 670 holly avenger or even a 600CFM universal holly would be better for fuel economy and still deliver performance with it really depends on what kinda performance he is wanting..i was recommending things to give like 75 to 100 horses over stock. mild performance gain.

Yes I agree with the Holly, a truck avenger preferrably, is a really nice carburetor.
But, Just because the q jet is a 750 cfm, dont be so quick to throw it in the pile because of the percieved bad MPG by wet behind the ears folks whom only have beginner experience.
The Qjet is one of the best carbs out there. small primaries, large secondaries, and the ability to achieve 23MPG on a C10, when set up correctly.
As far as heads, 193 heads are not slouches at all. are they high performance heads, No. but only a dumb ass buys a truck, to race against a Camaro.
I had t uned port on my Suburban for a while, with the 193 heads. I achieved 403 ft lbs of torque @ 4300rpm, but only 230hp...and that was while I was tuning the chip, so, it was by no means optimized.
The heads do wake up with exhaust porting, and 300+ HP has been achieved.
Vortec heads are excellent heads, But there is a drop off on torque in the off Idle range compaired to the swirl ports!where you want as much as you can get.
Vortec heads are basically LT1 heads, with the SBC cooling plan.

 

[lusktommy]

Yes I agree with the Holly, a truck avenger preferrably, is a really nice carburetor.
But, Just because the q jet is a 750 cfm, dont be so quick to throw it in the pile because of the percieved bad MPG by wet behind the ears folks whom only have beginner experience.
The Qjet is one of the best carbs out there. small primaries, large secondaries, and the ability to achieve 23MPG on a C10, when set up correctly.
As far as heads, 193 heads are not slouches at all. are they high performance heads, No. but only a dumb ass buys a truck, to race against a Camaro.
I had t uned port on my Suburban for a while, with the 193 heads. I achieved 403 ft lbs of torque @ 4300rpm, but only 230hp...and that was while I was tuning the chip, so, it was by no means optimized.
The heads do wake up with exhaust porting, and 300+ HP has been achieved.
Vortec heads are excellent heads, But there is a drop off on torque in the off Idle range compaired to the swirl ports!where you want as much as you can get.
Vortec heads are basically LT1 heads, with the SBC cooling plan.

thank you and i personally love rochester qjets but those large secondaries drink the gas haha..thats what i meant by the fuel economy part sorry for not making that clear. i couldnt agree with what you said though i have 2 rochester qjets in my shop that ive rebuilt and put away for 383 im building im gonna run twin qjets on it

 

[Stroked]

Eh what the hell, I'll throw my 2 cents in.

Is your truck a 2wd or 4wd? While I agree that Vortec heads are the best bang for the buck, you don't necessarily need them. Those tbi heads are way better than the smog heads from the 70's and early 80's. You can buy a carb intake for those tbi heads and make pretty good power and you would probably be pretty happy. BUT, I think it's a fairly expensive intake, so you might be better off getting the Vortec heads and intake. I personally would get Vortec's if I had the money. That's what will hopefully be going on my 350.

As for the carb, you're going to get a hundred different opinions on which brand to get so I'll let you decide. I will say that a 750 Holley or Edelbrock or whatever is a wee bit too much carb for a mild 350. Stick with either a 600 or 650.

Quadrajets are a great carb if everything is working correctly. I personally think they are the best carb ever made. Those large secondaries only drink the gas if you have a lead foot all the time. Lol. You'll almost always get better mpg out of a q-jet than you will a Holley or Edelbrock.

 

[lusktommy]

Eh what the hell, I'll throw my 2 cents in.

Is your truck a 2wd or 4wd? While I agree that Vortec heads are the best bang for the buck, you don't necessarily need them. You can buy a carb intake for those tbi heads and you would probably be pretty happy. BUT, I think it's a fairly expensive intake, so you might be better off getting the Vortec heads and intake. I personally would get Vortec's if I had the money. That's what will hopefully be going on my 350.

As for the carb, you're going to get a hundred different opinions on which brand to get so I'll let you decide. I will say that a 750 Holley or Edelbrock or whatever is a wee bit too much carb for a mild 350. Stick with either a 600 or 650.

correct me if im wrong but most stock to mild 350 dont even create enough vacuum to make the secondaries on a 750 Q-jet open to 100% in the power band ive always been told about 75-80% is that right or wrong

 

[Stroked]

A 750 Q-jet is nothing like a 750 Holley. That's the great thing about a quadrajet. Without getting too technical(and Jim can probably explain this better than I can), they meter fuel and air based on engine vacuum. Which is why you see them on anything from 283's to 454's.

 

[Jims86]

A 750 Q-jet is nothing like a 750 Holley. That's the great thing about a quadrajet. Without getting too technical(and Jim can probably explain this better than I can), they meter fuel and air based on engine vacuum. Which is why you see them on anything from 283's to 454's.

All carburetors work off of engine vacuum.
Here is a good read. Make sure you click the blue highlights, for example; the Bernoulli principal. Very important part of carburetors, but, the knowledge can be utelized in other places, like exhaust design.
http://en.wikipedia.org/wiki/Carburetor

My favorite 2 barrel carb, is the Ford 2700/7200, Variable Venturi carburetor. Yes, it was complicated, and you had to keep it clean(as you should any carb)... but once its set up and tuned to your engine, it is like a dream. No dead spots, no falling flat at high altitudes, and an Idle as smooth as a lake at 4am on a calm morning.

 

[Stroked]

Well, that's what I was getting at. Lol. I was just tryin to sneak posts in while working so my full train of thought wasn't in it.

 

[Jims86]

Well, that's what I was getting at. Lol. I was just tryin to sneak posts in while working so my full train of thought wasn't in it.

Nah, you got it right! Pretty good for a young fella!

 

[Stroked]

That Wikipedia article is good stuff. I'm gonna have to bookmark that for future reference.