Hi guys I have a question in regards to the mounting of a 390 cfm carb mechanical secondaries no choke on a Clifford intake manifold. I currently have a stock Rochester one barrel carb on it right now. I am going to be installing the new carb and intake in the spring. I have been looking online and everything I see has the carb facing east west vs the normal way it would mount on a V8. just curious if this is necessary for the carb to work or if I can mount it normally. right now the linkage for the carb runs on the inside of the carb.
Just speculating, but I would guess that the "East West" mounting is an attempt to equalize the mixture as much as possible. If mounted "North South" most of the mix from the secondaries would got to the North cylinders while most from the primaries would head South. It's pretty unlikely that the primaries and secondaries would be equally rich as the secondaries are "power adders" and typically jetted richer.
A carb with primary and secondary circuits typically runs off the primary circuit until you get on it. Then the secondary circuit opens up and provides more air and fuel to the engine. If you mount the carb north/south on an inline 6, one primary and one secondary will be closer to the engine and the other pair farther away. This will also place the primaries closer to the front three cylinders of the engine and the secondaries closer to the rear three cylinders. This will negatively affect the evenness of the charge getting to the cylinders. When you mount the carb east/west you have one primary and one secondary feeding the front three cylinders and the other pair feeding the rear three. This also allows each primary/secondary pair to feed every other cylinder in the firing order. The same reasoning applies to inline 6 headers or splitting exhaust manifolds
With the Aussie Speed intake I have for mine I am not sure that it makes any difference which way you set the carb on as that one may have too much volume and flow. I was figuring on putting the carb on in and east-west orientation though. It's not going to be a race motor but will have lump ports and a decent cam,
I suspect its more convenient for the throttle linkage to run north/south so that would determine the carb position. Air/fuel flow would not be an issue as the intake lengths are different anyway. On a V8 all the intake ports are a different distance from the carb choke. Not worth overthinking it.
Some schools of thought say that you are correct, Low pressure in the cylinders is what moves the fuel and air anyhow. Low pressure created when the piston goes down in the bore on the intake stroke.
I have a similar combo in my avatar 41 Chevy....I6 Chevy 292 with a 390 Holley. I had to rotate the carb 90 degrees because the linkage on the carb was too far to the drivers side to line up with where the gas peddle cable would come through the firewall. Works great though.
My vote is for North/South, like on a V8 and here's why, fuel distribution notwithstanding: If the carb is mounted sideways the acceleration and deceleration of the vehicle will cause the fuel in the bowls to slosh fore and aft. (I should clarify this by saying that I assume the bowls have side-hung floats.) That will cause the floats to close up the needle and seat, restricting fuel just at a time when fuel is needed most - during accels. That will cause a hesitation. With center hung floats it is not as big an issue, although it can still happen, especially on hi-G launches like in a drag car. Aftermarket carb float manufacturers sell an array of specially countoured float shapes to mitigate these effects, with varying degrees of success. As far as fuel distribution goes, it is my opinion that it matters little which way it is orientated - the center cylinders get more fuel regardless and the end ones get less. On my inline drag cars, I've had the best luck using a 4-hole spacer under the carb. On the Aussie intake pictured, I agree with Mr48Chev that it looks to have an awful large plenum volume for a street driven vehicle. That would be tantamount to running a tunnel ram on a V8 street driven rod. Do-able, but not optimum.
Throttle response is going to be terrible. The Aussie intake has way to be of plenum and runners for a street driven low rpm engine. Even the Clifford intake is considered big compared to the Offy intake. The air velocity will be so slow, most of the fuel will drop out of suspension before it gets to the ports. Chuck a turbo on with some big boost and kick the rpm way, then yes, both will run pretty good. Here is how Pontiac mounted the four barrel,
thanks for the input guys. yeah I had a feeling that it had to do with the air/fuel mix. I'm going down for a week in the spring to my uncles place whose been messing with motors since he was a kid. If mounting it sideways works better for the mixture and makes the car run smoother and it's not a complete pain in the ass to run the linkage that way I will do that.
hey guys have another question in regards to the linkage. just for bit more clarification. The transmission I'm running behind the chevy 292 in my 1953 chevy 210 is a 700R4. I dont want to change the linkage for the throttle for the transmission. On the Clifford I don't see any sort of boss or threaded hole that I could use to take the old linkage for the new intake/carb combo. is there any sort of a prefabbed linkage kit I could use or have to slightly modify to run the carb the way it faces now I could make it easier for myself and run the carb north south vs the way it sits east west but if running it the way it mounts to a v8 is gonna cause the carb not to run right I dont want that either
The intake is a single plain, so it won't matter which way you mount it, the fuel will find it's way to the cylinders. Where you might run into trouble is auto-cross style driving or hard launches at the drag strip if it mounted sideways. Mount it the easiest way possible for the transmission linkage to work correctly, or you will be rebuilding it after it burns up from a misadjusted cable. Look at some of these, https://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=throttle cable mounts you should be able to find something to work no matter which way you mount it.
The Jalopy Journal
