The Stovebolt Site Forums The Shop Area Engine Shop Carb Orientation on Manifold + Radiator

Hi All,

I found a great article by Jason Sternhagen that details a kool 4-barrel throttle linkage for GMC and Chevy Inline engines. I have a 270 and want to use this set up versus a cable type arrangment. In the article, Jason sets up his carb with the primaries to the outside of the engine. Mine is installed with the primaries to the engine side and runs fine, in the barn under no load. Here's the question, is there a right and wrong way to mount the carb?

Also, can someone tell me were the springs used on 47-54 GMC radiator bottom support go. I beleive they were below the center cross member when i removed them?

Thanks

Grant
50 GMC coming along
45 Burb just starting

Generally, a four barrel on a six would be mounted with the primary side toward the engine. I cannot recall previously seeing a carburetor mounted with the secondary side toward the engine.

If the manifold were designed for it, a better way would be to have the primary side toward the radiator, as most 4-barrel carbs are designed for mounting in this manner. Depending on the design of the carburetor in question, fuel slosh can be a problem when rotating ninety degrees to mount on an inline six.

Jon.

Carbking's reply is correct in my experience.During the last few years I have run several different 4bbls on my 261 powered 37 truck.I found when the carb was mounted V-8 style, primaries foward, low speed response and idle was better than when the carb was turned 90 degrees with the primaries away from the engine.Wide open throttle performance was the same either way. I'm using a Clifford manifold, which has an open plenum design, probably less sensitive to carburator position.The AFB and Edelbrock when mounted sideways, would have a tendency cause the engine to stumble when the truck was braked, the Holly 4bbl less so.Maybe on another engine, another vehicle, the results would be different.Position the carb the way it works best for you.
Yes, the core support tension springs go on the bottom.

Using a quadrajet would allow you to mount it sideways and keep it GM simultaneously. They have a central fuel bowl. I used one on my jeep CJ-5 and it worked great. They are not as bad to tune as most people think.

Thanks everyone. I guess I'll just play around with it. Secondaries to the engine is the easiest for the linkage hook up. Haven't looked at secondaries to the rear position. It's a holly 390- square bore on one of patricks 4-barrel intakes. Seting it up forward might make a difference but with the center hung fuel bowles it may not matter anyway. Guess I'll know if I get it wrong by the way it resonds during accel and braking. Won't be on the road for a few more months so i can always change it back if need be. Thanks also for the info regarding the springs on bottom of the radiator.

G

The quadrajet is an often-overlooked carburetor. It is a wonderful carburetor for the street, and can be modified for racing or autocross. The biggest problem with the Q-Jet is that GM never sold them aftermarket, and never tried to market individual performance parts. If one were going to install a Q-Jet, one from an O.E. application of similiar displacement is a good idea. Pontiac used a Q-Jet on the Sprint option OHC 6 in 1966 through 1969. The 1966 and 1967 were 230 CID; the 1968 and 1969 were 250 CID. The design of the 1968 and 1969 carburetors is better than the earlier design. There is an excellent book on Rochester carburetors, called 'Rochester Carburetors' written by Doug Roe and Bill Fisher, published by H.P. Books.

One need not be intimidated by having to change the travel of throttle linkage. If the linkage pulls to open and needs to push (or the other way), simply machine a hole in the throttle arm on the other side of the throttle shaft (if the present hole is on the bottom, bore one on the top). Like a child's seesaw, this will reverse the travel.

If the travel needs to change ninety degrees (at right angles) it is still no big deal. Simply machine a bolt to set where the throttle linkage and carburetor linkage cross. The bolt should be machined to have a smooth shaft of three-eighths inch ABOVE the bolt. Now machine a piece of flat steel stock in the shape of the letter 'L' with the legs of the 'L' each two inches long. Bore three holes in the 'L'; one at the end of each leg, and one in the 'heel' of the 'L'. Slip the center hole of the 'L' over the bolt and attach the throttle linkage to one end and the carburetor linkage to the other. Moving the throttle linkage will cause the 'L' to rotate, thus moving the carburetor linkage. Bore a hole in the top of the smooth shaft above the 'L', and install a cotter pin to retain the 'L'.

If none of this makes sense, give me a call during normal business hours.

Jon.