Making the change: 2BBL to 4BBL

[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.