Hello, I was wondering if doing a 2bbl to 4bbl swap on my 1970 350cui. is a smart move to gain a little bit of performance. If my memory serves me right, I was reading that I must do a cam swap as well to match the 4bbl intake, or else the power gain won’t be there. Is this true? Has anyone done a 2bbl to 4bbl swap without a cam change? Has there been any performance gain/loss? Thank you for reading
No reason to need a cam change from 2 bbl to 4 bbl. You CAN change the cam if you want, or if its worn, you can upgrade, but its not needed to go to a 4 bbl carb.
I'd imagine the basic increase in seat-of-the-pants feel when the secondaries start to howl. I would certainly make sure to completely and diligently retime and tune the engine with the new carb for maximum benefit before you hit the street.
I did a 2 to 4 barrel swap on my 68 350. I like it. It runs great. No complaints. Swapped from a cast iron intake to ta performance aluminum intake. Went with a 750cfm quadrajet. Pretty simple swap. A cam would be beneficial too. If not, it's still a nice upgrade. You can put together a parts list via this site if you decide to go that route.
On the other hand, as long as you would already have the intake off and if a cam swap is in your budget then I would consider that the best time to do it.
I think the swap is your only realistic "performance upgrade" option. Dual exhaust and re-curve distributor will help the combo, too. I'm sure you will never consider going back after you make the change.
Hey hey woah, that’s crazy talk. One does not simply stop at one modification. Next thing I know, I’ll be taking apart the valve train! Jokes aside, I do get what your saying. Thank you!
A good Quadrajet is a great idea. This is one modification that's a win-win move. You will gain performance, and if you keep your foot out of it on trips, you may well see improved fuel economy - especially if you install a good dual exhaust system. I did the same thing with a '62 Chrysler 383 and picked up mucho performance and about 3 mpg better fuel economy on the highway.
There is no difference in the camshaft on 2 and 4bbl engines, it's the same. If you do the 2 to 4bbl swap, make sure you go to a nice dual exhaust as well. In fact, I recommend you do the exhaust first.
Secondaries are classified as a gateway drug. The sweating hands, increased heart rate, faster breathing, drooling, the glazed stare, the uncontrollable urge to stomp the flat pedal flatter...
I made the change. 4 barrel Quadrajet and dual exhaust. If nothing else it makes the car look and feel right and the car fans seem to appreciate it more too.
