Making the change: 2BBL to 4BBL

[MosportGreen66]

I am strongly considering making the change on my Camaro from a 2 barrel to a 4 barrel carburetor. I am not looking to make the Camaro into a hot rod, just looking for more power, while utilizing basic bolt-ons. Before I invest money in parts and hardware, I thought I would ask the community for some help with my homework.

Here is what I have to work with:
L-65: 250hp, 350 cubic inches (2 bolt main)
Turbo 3 speed trans
All stock, original internal engine components

Will the addition of a new intake/carb set up affect any power assisted options?
Mechanical Options Include:
Pwr Steering
Pwr Brakes
Dealer a/c

Will the addition of a new intake/carb set up affect the distributor, coil, or fuel lines?
If so, what will need to be changed?

Besides updating the carb and intake, what other mechanical pieces am I going to need?
Will I need to change any internal engine components? If so, what are they?

I would like very much to work with original appearing parts, what do you recommend for an intake? Carb? Air Cleaner cover, base, etc? Any past experiences you guys would not mind to share? Thanks very much guys!

-Dan

[Salvatore]

I would go with an original cast iron intake and Quadrajet. I think your throttle linkage will hook up and trans kick down if you have an automatic. I am not sure of the fuel line but that is simple to fix. All other componets should bolt right up. You can get dated intakes and carbs fairly cheap. You can even get your choke to work. All internals should be the same. Basically the same motor. Good luck. Sam

[WILMASBOYL78]

Simplest route would be to use a Q-Jet intake and carb form that era. Since the 350 motor was available with that set up the linkage and mounting issues should be minimal. You don't need to make changes to the internals unless a cam upgrade is of interest. Here again there are many hyd. cams available to give a boost over the stock unit. I would also suggest having the dist upgraded with a petronix or crane setup while it is out. Looks stock and eliminates the points hassle. Also check the curve and vacuum advance on the dist while it is out and have someone set it up for optimum performance with your car.

wilma

[Seattle Sam]

Dan,
I second Sam! The Q-jet is a very driveable carb with a good choke, and with the small primaries / large secondaries it is fairly fuel-efficient. It also makes a cool "honk" through an open element air cleaner when you put your foot into it!

The cast iron manifold for a 1970 350 4BBL (350/300 hp)is 3965577.
The carb you are looking for is 7040402 (non-California 350/300 automatic)although any Rochester QuadraJet will look OK. This should work fine with everything else under your hood.

Or, if you want to spend more money you can get the aluminum 3972110 (1970 LT1 intake). The carb for this is a Holley 4490. However, most would say this is more carb than you need for your motor.

(Thanks to Alan Colvin, Chevrolet by the Numbers 1970-75)

-Sam

[MosportGreen66]

Whoa! Thanks guys!

The Holley carb on the Convertible is not correct for the car. I was thinking it would make a good candidate for the Camaro? The convertible is an L-79 327 ci, 350 hp car. What do you think?

-Dan

[Salvatore]

Put the Q-Jet on it. Simple and never fails. All linkage hooks up easier. JMO Sam

[Kurt S]

I disagree with y'all.
Everyone swaps 2bbl to 4bbl, but I doubt you'll see any performance gain. That 2bbl is more than keeping up with the engine.
I'd suggest rebuilding the distributor (vertical lash and advance tweaking) and tuning what you got.

[Jeff H]

If you're gonna change to a 4 bbl, do a cam swap as well. Otherwise the gains will be minimal like Kurt said. Even with another cam, the heads are probably limiting the potential with small valves. So do the cam, heads and 4 bbl. Or do nothing(it's cheaper). I would look at the ignition system as the best place to pick up some performance.

[Pantera]

Jeff I hate to disagree with the head statement but you are not going to pick up a great deal of noticable in the seat of the pants HP by changing the heads on a low compression street car. If you had the motor on a dyno it would be such a small gain that the cost would not warrant it. Heads only make a difference above 4,000 RPM.

In my opinion a good mild Hyd cam and a four barrel carb with the timing set up right, makes for a very drivable street machine with out spending a small fortune.

Pantera

[Salvatore]

Put the Q-jet and cast intake on. Have the distributor rebuilt and if everything else is where it should be and up to the correct tune up, the car will perform good with NO complications. Don't need to change cams, heads, headers, etc. Clean it up and paint the engine to look nice. Make it a one day project. Don't need to over engineer it.