[JACK_BURTON55]

I have 2 Qjet carbs here
Carb numbers:
17059272 - 79 301 auto car
17054931 - 74 chev 350 or something

Now currently on my 76 Firebird i have a 2bbl setup, car is an automatic and the brakes are ran off of a vacuum line fitting coming from the back of my 2bbl.
The 79 301 carburetor which is the one i would like to use has no hole large enough for the fitting that comes off the 2bbl carb. (fitting connects to a line that runs to the brake booster/master cylinder)

However the chev carb's base has a fitting hole that looks big enough for the fitting that is currently on my 2bbl.

My question is can i change out the base plates from the 2 carbs and have everything work properly or is there a way to make the 79 carburetor work with my brake setup. I would like to step out of the realm of 2bbl and into 4bbl. Thanks!

here is a picture of the bottom of the 79 301 carb

here is a picture of the bottom of the 74 chev carb

[Mark1968]

They look like different baseplates. It's probably best not to mix and match here, things on these carbs change from year to year.

I have a chevy q-jet that I could never get to run right, eventually found out it was 2 different carbs pieced together.

[Overkillphil]

You can use an adaptor fitting readily available from a Hardware store or Home Depot, etc. There are alot of easy ways to deal with the fitting issue on the back of the carb. As Mark said, don't mix the baseplates.

I would also use the 79 Pont. carb.

[77 TRASHCAN]

THE 79 CARB IS A MUCH BETTER CARB. IT HAS THE APT.
IS THERE A HOLE IN THE BACK OF THE 79 CARB? IF NOT, OR IF IT IS TOO SMALL, DRILL IT AND TAP IT. JUST TAKE YOUR TIME. THE CHEV CARB LOOKS LIKE 1/4" PIPE THREAD. ANY PARTS STORE SHOULD HAVE ONE.
DID YOU GET THE BOG OUT OF THE 2 BBL CARB YET???

[JACK_BURTON55]

hey guys! first off happy new year, ya i did manage to get the bog out of the 2bbl carb. JB welded the hole works great. . for now lol.

Yes the 79 carb has a hole but it is very small. the adapter on my 2bbl takes a 5/8 wrench. the hole on the back of the 79 carb is about half the size of that. and is plugged with a screw that turns with an allen wrench. how were the brakes ran on the car this carb came from? or do 301s just not make enough vacuum to run vacuum brakes? strange either way but you guy think i can use this tiny hole to work my brakes? i really would rather not mix bases, it was just the first idea that came into my head.

[77 TRASHCAN]

THE PIPE PLUG IN THE BACK OF THE 79 CARB ISN'T SOMETHING I'VE SEEN IN A STOCK CARB BEFORE...WHO KNOWS..
I AM SURE YOU CAN OPEN THE HOLE UP TO 1/4" PIPE THREAD. (PIPE THREAD IS TAPERED, DON'T TAP TOO FAR INTO BASE PLATE TO START WITH, GET SOME DRILL BITS, ONE THE SIZE OF THE SMALL END OF THE PIPE TAP, AND A FEW THE SIZES BIGGER, JUST DON'T DRILL THE HOLE TOO BIG TO START WITH.
SOME VACUUM SOURCES CAME FROM PORTS IN THE INTAKE MANIFOLDS.
YOU COULD ENGINEER SOME FITTINGS W/ THE SMALLER HOLE, IT WOULD SURE BE NICE TO USE THE PIECES THAT CAME ON THE ORIGINAL 2BBL, THAT WOULD BE MY DIRECTION.
DO YOU HAVE CLIFF'S BOOK???