Hello all, this is my first post to the forum. I have a 1971 Olds Cutlass, 350 2 barrell, automatic, 56k original miles. I searched the forums and found a few threads that work around this question but the one focused more on the trans swap so hear it goes...

What do I need to buy to convert my 1971 350 2 barrell to a 4 barrell set up? I have purchased a 1971 4 barrell intake, and am debating which Edelbrock carb to be either square bore with an adapter or spreadbore.. What else will I need to do this all at once? thanks for your help

 

X2 - I am a curious novice as well.

 

I would find a rochester 4v for your stock manifold. I have done this using an edelbrock and you will need the spreadbore to squarebore adaptor. It's about 3/4" thick. I'm not saying that the edelbrock carb won't work, it will work nicely. But after playing with both carbs on my 330 for 2 years, I found that I liked the rochester better for all around performance!

 

X2 on the Q-Jet!
Since offered stock on the car, all factory parts can be used, without modification.

 

So just a carb, everything else is a direct bolt on then?

 

NO!
I did a 2bbl to 4bbl swap in 2008. I used a
- 7042250 quadrajet - restored ( I believe the one for 71 is 7042150) Also need the base gasket and air horn gasket.
- 4bbl quadrajet fast idle solenoid (will plug directly into same connector for 2bbl one)
- 4bbl intake manifold - I didn't play around with adapters. A stock 4bbl intake manifold for your car is cast iron and is designed specially for the Q jet. It weighs a lot though. If you decide to go to an aftermarket that's ok too, just so long as it's designed for your engine and 4bbl carb
- 4bbl throttle cable (different than 2bbl)
- 4bbl throttle cable bracket (bolts to back 2 bolts of carb - it's different than 2bbl)
- new intake manifold gasket set
- 4bbl air cleaner (2bbl will not fit. The air horn is different diameter)
- replace thermostat/gasket and connecting hose
- transfer water valve at back right of manifold, or buy new one.
- transfer idiot light/gauge sensor to new intake

That's pretty much it. My car is not AC. You will also have to play with the fuel mixture to get the right settings for a 4bbl. They are in the 71 CSM if you need them.

 

Either get a Q-Jet or a Holley 4175 spreadbore for the manifold you have or get a 65 4BBl intake if you want to run an Edelbrock, it bolts right on. What ever you do don't use an adapter plate.

 

A good carb for the street, works on either square or spread bore intakes, is the new Street Demon. It is basically a modified Thermoquad, with either the plastic(polymer) or aluminum main body. They made it a 3 barrel so it would flow 625 cfm and still fit a square bore manifold. It has small primaries and will be very comparable to a Qjet mileage wise. Holley now owns the Demon line, so quality issues should be gone.

 

Allan, you forgot to tell him he'll need a new fuel line, too, unless he can wrestle the original into the right position.



- Eric

 

I already have an intake (cast iron) and have been looking at some aftermarket spreadbore carb (I have had an edlebrock for years on various cars and never had a single issue with them so would like to stick with them)

 

D'ohhh!!! Yup slight brain fart there. If he tries to do that he'll probably end up putting a bad kink in it or cracking it. My bad - thx Eric!

 

Thanks for all the help guys

 

If you have a rebuildable core Q-Jet or want to buy one done check these guys out.

www.everyday-performance.com

I had them rebuild my Edelbrock QJet and was pleased with the work & the price.