I am getting ready to switch from a 2 barrel intake to a 4 barrel stock intake. Does the metal pan under the intake have to be installed. is there a gasket set without it i can order. also is there a difference in the two barrell and 4 barrell heads as far as horsepower
Hi David, The metal pan style gasket is required, since the pan deflects oil away from the PCV valve which is inserted into the intake manifold behind the carburetor. You can purchase "paper" type composition gaskets, but then you still have to devise a way to protect the valve from oil splashing. The easiest plan is just to use a stock replacement steel gasket. There is no difference in cylinder heads between two and four barrel that I've ever heard of. You will love the upgrade you're planning. Devon
thanks for the help one last question what size rochester is best to use or the holley equivalent. I am planning on adding a better cam since the motor only has 80,000 on it now
The best thing you can do to begin with is to find a Quadrajet already calibrated for a Buick 350. We can talk camshaft once we have more info about your car and what you'd like it to do, but some other upgrades (ignition advance recurve and exhaust in particular) should happen first. Devon
may want to check in with ken @ everyday performance . check down below in the vendor section . never heard a bad review that i can remember . just got an 800 from him . nice guy - fair pricing . others out there probably fine also - cliff is excellent but seems to be busy always , which in itself is a good review . would be an excellent time for some basic port matching and maybe some plenum work depending on time/skill/needs .
You can get composite gaskets and modify your existing pan if you want the composite type gasket. AM&P makes a valley pan piece that will work also. The pan is necessary for the PCV valve. And yes, get a 750 cfm Quadrajet. I have several here too and build them if Ken can't help you out for some reason.
if you want to use a holley carb and want the right answer on what cfm carb to use go to their website and they have a calculator which will ask questions on engine mods type of driving,rpm range of driving etc.....these are the people to get the right answers.....most people tend to use too big of a carb for the engine and are actually producing less not more horsepower.......the rochesters that came on the car most were 850 cfm BUT!!! the primaries very small which accounts for their fuel economy and that is where most of your driving is done.....when their secondaries are engaged the cfm is calibrated for the specific engine.....aftermarket carbs have larger primaries which if the carb is too large only gas wash the engine......in NASCAR's former BUSCH NORTH series and Modified series our carbs were limited to 390 cfm and our engines could put out in excess of 600 hp out of a 355cu engine
Some of us have done track and dyno testing on Buick 350s, so trust us over a calculator.:beers2: The Q jet carb that came on the Buick 350s were 750 CFM just to clarify. In the later 70s the Q jets were 800 CFM. Do not bother with the calculators, use a 750-850 CFM carb on a Buick 350 if you go Holley. be prepared to re-jet the Holley to make it work and fuel milage will be lower than the Q jet.
Yes. listen to Sean, ignore the sugestions of carb. cfm from the calculator. Buick/GM/Rochester spec'd a 750 cfm carb for the Buick 350. Why go smallerou:
Hence my suggestion to find the correct Quadrajet carburetor for a 350 Buick. All too often the lack of q-jet understanding makes a quick path for a person to buy aftermarket. It's tough enough for us owners of older cars to find a carb that's right for a 2v to 4v swap like this. These parts seemed to grow on trees in the '80's, but no more. Realistically speaking, a stock 350 Buick may not need 750 cfm, but there's the beauty in the q-jet design...even though the throttle blades may be wide open, if the q-jet is properly calibrated as Buick intended, the secondary air valves will only allow what the engine wants. Even better is that the q-jet meters fuel with the air valves, something an aftermarket Holley cannot. Lastly, a 600 hp engine relying on 390 cfm for competition is an engine designed around it's restrictions. We already know why the restrictions were put into place. How much output would you get if you designed the engine around a 600 cfm input? A lot more, I'd suppose. Rant over, you guys already said it better than I could. And I'm a Holley guy. Devon
Devon you are almost close to right about the 390 carb and engine but the the engines are not changed were not changed from when we used the larger carbs....what NASCAR did to us was take a larger holley which cost approx $1000 set up to $3000 carbs in the 390 cfm ......we had to adjust gearing to compensate for where the power now comes on in the car.... the reason for recomending to use the HOLLEY website calculator was that it is a good starting point....from what i saw with the initial question is that he was going to change from a 2v to a 4v carb an intake with no other substantial changes.....i have been around many engine builders and tuners in NASCAR drag racing and street rods and they all seem to say that one of the biggest problem is that people think that bigger is better without conideration of the whole package......they run the wrong carb, wrong size exhaust,wrong cam profile,wrong gearing in any of those combinations to what the use of the vehicle.......a street car which runs at lower rpm's will require a different setup than a drag car which will run at much higher rpm's...... and yes not only have i seen this on engine dynos but chassis dynos [which give the hp and torque to the wheels] and have seen more over carbureted engines that just fell short.... this is the reason i recomended the HOLLEY site.......they are the engineers and have tested these units for specific uses......that is a good baseline then you build from there......Devons insite on the rochester is right and as others have said the right rochester calibrated to the right engine is pretty hard to beat for a good street application with decent gas mileage.....one last thing if what you are running on your car works well then you nailed it but one thing if found with engines especially higher performance engines is that you can build 5 engines to the same specs and dyno them all and have 2 that have 1 type of hp and torque ,2 that react differently and the last one is a totally different animal to them all
The Buick always liked a bigger carb than what was suggested by the Holley calculator. Even the 350 came stock with a 750 Q-jet. I used a 750 Carter AFB and a Holley 750 Dbl pump at the time I had the engine rebuilt. On the dyno the Carter gave me 365 hp and the Holley was at 395 hp.
as i said before if it works for you then that is the way to go......like i said before our race team used to rent out its chassis dyno and have dyno tune days where we would tie down the cars and do a pull......our engine builder and tuner would be there and soo many times guys were over carbureting the motors and not putting out what the engines were capable of.......our team owner also had a speed shop located in the next building to the dyno shop would provide different carb combinations to try [nice way to sell parts] and do another pull.....alot of people were surprised with the results....yes i never did see this done on a buick but i did see a bunch of pontiacs and olds go through with similar results....dont get me wrong i am not contesting anybody's setups or results if you are having good results with your setups than thats the way to go.....i am only stating what i have seen on the chassis and engine dynos [ more so the chassis dyno] and also am repeating what engine builders have told me
I have one of those old badboys. Flop those two big back barrels open and booooooooooo... On the old stock motor with the one whellie peelie and that comp cam 268 it would burn that tire for a block.
