350 2bbl -> 4bbl carb

I'm totally new to this game. I just upgraded to dual exhaust on my '72 Skylark, but now I want to get more air coming in. Is switching over to a new intake manifold and 4bbl carb pretty straightforward? What should I look for/be aware of when looking for a new carb and manifold? I've done a bit of searching on the site here, but I couldn't find an exact answer to my question. Also, can anyone recommend a good book on carburated engine mechanics for an eager learner? Thanks!

 

Hi Mike, welcome to the boards. I'm originally from up around there, Westfield to be exact. A little bit out west from Boston so I don't have the wicked accent!

A good book is "Rochester Carburetors" by Doug Roe, around 20 bucks I think.

I just did this swap myself a few months back. I went with an original cast-iron (thing is damn heavy) 4v intake and a rebuilt Qjet because I wanted better performance on the cheap. If money is not as much of an issue as it was for me, you can go aftermarket for an aluminum dual plane from Poston or TA Performance. Beware these are not cheap, I think upwards of $300 whereas I got a nice original bead-blasted intake from a kind gentleman for under $50 shipped. Check around here, the Buick community really supports each other well and people will cut you a break.

For anything other than the Qjet like spreadbore Holleys and Edelbrocks you would need an adapter. You can get these for around 20 bucks with studs etc. from the local parts store. You may also need to pick up a variety pack of those little "linkage balls" for the throttle, I did when changing over. I'd suggest getting an already rebuilt carb or something easier than a Quadrajet in need of a rebuild kit. The kits come with instructions good enough to get you through a rebuild of ANY of these carbs, but I had other tuning problems that I never resolved with the Qjet. I eventually went to Edelbrock and forgot about it since the difference was almost night and day.

The gasket set will include an intake/lifter valley pan-type thingy. What I tried to do was use the supplied RTV to set it up on the heads for a while before installing the intake. All this done after I cleaned the ports on the surface of the heads with a putty knife. Be sure to keep a hand towel or a vacuum handy for all the little bits that would drop into the lifter valley. Anyway, I found that it's probably best to just try to do it all in one shot. RTV at the edges and corners of the front & back rubber gaskets, around each port and the water jackets, careful not to get any stray goo in the water passages, set the intake on and tighten/torque.

When torquing, I usually start from the center and don't tighten down all the way at first. I do it maybe 4 times, each time tightening gradually and working in a circular pattern outwards. Doing it this way should distribute the load more evenly and help prevent any leaks or stripped threads.

What else... I had to do a little creative and extremely careful bending of my hard gas line. I eventually had to go to rubber hose -> filter -> rubber hose -> carb setup because I ended up swapping the carb to Edelbrock but the Qjet uses the hard fitting straight to the carb just like the 2-barrel. I also had to cut and re-run a new rubber hose for brake vacuum since the original wasn't long enough. Thankfully you probably won't have to mess with kickdown adjustment since it's all on the pedal. If you go with Qjet make sure you use the stone filter in the front fitting if you retain hardlines all the way to the carb. There are no other filters in the fuel system down the line. Of course, a new air cleaner is in the works so why not get a nice shiny new one with a cool little Buick sticker on it?

Another great resource for instructions on how to do mods and stuff is Buick Performance They have tons of tech articles up there and I've used a few so far.

Any other questions, feel free to ask. There are MANY more knowledgeable people on here than me to help!

 

Wow, thanks for all the detailed info! I'll grab that book for sure. What is an RTV? I've read conflicting things regarding air cleaners. Some people say to pull the stock cleaner, bolt on a new less restrictive one (what do you do with all those hoses?) and add a little intake filter on the valve cover. But others say using the stock housing is important precisely because of those vacuum hoses and such. Is someone making a correct style 350-4 air cleaner housing for Buicks or am I looking for an original?

 

I'd find a 4bb stock intake snorkel, they come up on e-bay all the time.

 

4 barrel

Hey Michael here is a little comparison experience. My dad bought a new Skylark in 1970 and drove it until 1978 and decided to put dual exhaust on it. Nothing high tech basically stock. There was a noticable difference in the performance and mileage. It drove like a different car. I had a 65 Skylark convertible that I put a 350 in drove it a couple years and pulled it out for a rebuild. it was a two barrel engine. It went back together with stock rebuilder cast pistons a Poston 114 cam and a factory 4 barrel manifold rebuilt quadrajet and 3.42 gears.The car ran great, after a few months I took it to Bremerton raceways and made a couple time only runs 14.98 and 14.95. I realize you aren't trying to build a race car here but just trying to give you an idea of how little it takes to make the little Buick 350 respond. :TU: Have fun

Bob Harris

 

The RTV that OneBadBu is talking about is gasket sealant

 

Yep keep the original snorkle intake...you want cold air going into the carb and not the hot air being pulled in from the fan across the radiator.

I also went with the Performance Holley carb due to tuning issues with the Qjet, it's a nice bolt and pray item and the parts store had the adapter plate and linkage studs I needed to set the carb up.

Wayne S

 

Hi just following up on this how did the swap end up going?? I have a 72 350 2bbl and im in the same position, new to the buick scene and looking to get some better performance out of this beauty. The car will be a daily driver so dont want to start messing with internal stuff too much, looking for solid and reliable while fun to drive. Thanks for any help and info!!