carb and intake on 350

I've been thinking of upgrading my current 2 barrel Rochester on my 350.  I'm reluctant because the engine is original but i'd love to get more horsepower out of it.  i've heard from different sources that if i put a 4 barrel carb on it, it will get better gas mileage too if i can keep my foot out of it.  is that true?

I'd like some advice as to what kind of carb I should get.  A friend gave me an intake for free.  it reads 485912.  will that fit my 350?  Also should i try to find a rochester qjet to fit it or should I go with a holley carb?  

As far as carbs go, i've seen them listed with specifics like, " went on standard transmissions."  Does that mean that carb only has hook ups for standard transmission cars?  Do i have to find a carb that is specifically set up for automatic tranny or is that just a numbers matching thing?

thanks in advance  

The intake is originally for 1972 350/400/455.
Better gas mileage with a 4bbl carb. I very much doubt that.
If you intend on using a factory intake then I would go with a q-jet for auto trans. but if you plan on using a aftermarket intake then go with a holley.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

if i upgrade to a four barrel qjet using the factory intake, how much more horsepower will i gain?  what if i go with a performer intake and a holley 650?  what combo would  give me the best return?

also, i was skeptical about that 4 barrel / better gas mileage thing.  i know i could never keep my foot out of it.  i'd be stomping on that pedal all day.  i just have to make sure not to let the wife drive.  she weighs about 100 lbs  and 90 of it is in her right foot.  you'd think she'd be able to talk he way out of a speeding ticket, but i guess she just has a guilty face.    

Hahahah.  Yeah, I don't know about getting better fuel economy by switching to a 4bbl, but who cares?  It will definitely perform much better.  I would do the Edelbrock performer + Holley 650 combo, in fact, that is what I am planning to do with mine.  I think the Holley is a simpler carb to work with, and the Edelbrock will outperform the stock 4bbl intake.  
1969 GTO, YS code 400, 350hp/445 ft lbs of torque (stock specs), LT headers, H-pipe, 750 Holley 4160, Ignitor II ignition.  Complete Painless wiring.

I have a 76 400 with a performer intake and holley spreadbore 650(part # 0-80555C), it did have the stock intake and qjet carb on it(probably in need of a rebuild).  The holley has much better throttle response and my fuel mileage went from 8 with the qjet to 12 with the holley.  I have been told that a 4 barrel does increase mileage if you keep your foot out of it because first of all the primaries are smaller on a 4 barrel than on the two barrel which uses less fuel and increases velocity, this leads to more torque and fuel mileage.  

For the best power I would get a edelbrock performer intake and a holley carb. if it has the stock cam you will not see a big increase in power by just going to a 4bbl carb. but if you change to a bigger cam then the 4bbl with the edelbrock intake will work very well together.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

I heard that when going to a bigger cam i will lose vacuum.  will this affect my power brakes or give me other vacuum issues?  if I go with the bigger cam, would I have to get a vacuum pump or something?  

oh, and just out of curiousity, would a tri-power set up work on a 350?  

You will lose vacuum with a big cam but if you go with somthing like a .450-465lift you will be just fine.
I would recomend a lunati .458 lift cam kit.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

P#Lun-00072LK would work very well.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

The better mileage comes from using a Quadrajet as the primaries are quite a bit smaller than the ones on the 2 bbl.  This is only if you never put your foot into it, and what the hell is the point of that??  Quadrajet, Holly, Edelbrock will all work great.  The tri power will work on the 350, but it is a very expensive option.  You can get a great intake and carb for around $600, compared to more than $2000 for a tri power setup.  Just remember not to over carb your car.  600 - 750 cfm should be just about right.  Hope that this helps.

AK  

I think i'd like to use the '72 intake manifold since I already have it sitting around.  can i put a holley 600 on it ?   also, i'm fuzzy on the details about different carbs.  i see them listed for sale with specs like  for auto trans or manual trans.  does it really matter what i get or do they have different hook ups?  

If you're gonna use the '72 intake you'll have to use an adapter because of the carb bolt pattern on the original GM intakes. Go with an Edelbrock performer they cost about $210 for the performer and $220 for the perf. RPM, Edelbrock carbs will run about $290 for electric choke and $270 for the manual choke (600 cfm). Personally I would choose the edelbrock-edelbrock combo. If you choose to stick with the '72 intake you'll need to find a q jet or a spreadbore(4150) to peanut-bore adapter to run an aftermarket carb. Also if you're running an automatic trans you'll need to have the kick-down cable hooked up to the carb throttle linkage for the passing gear, this also increases the line pressure on the internals of the trans so that it doesn't burn up the clutches because of excess slippage, so this is a must-have with automatics.
What trans is in the car?  

i have a Turbo400.   i was thinking about getting a holley 600 and the guy selling it states he has the adapter for the quadrajet intake and is willing to just give that to me.   if i go that route, i need to find a way to connect the kick down cable i guess.  i probably need to get a book or something to read up on all that stuff.  any suggestions on what and where to get good information on setting up a carb?  

There's a bracket that goes on the carb throttle linkage so that it has the right "pull" on the TV(kickdown) cable. Check out Summit, Jegs, PAW (your neck of the woods) or your local speed shop for this bracket. I've always been told that when the carb is at WOT, there should be no pull left in the TV cable. Should be simple enough right?