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Hope you report back when you find the vacuum leak and where it was. I've rebuilt the carbs on mine numerous times over the years. I struggle with how any vacuum leak at the carb could fine it's way to the diaphragm that opens the carb.
The fact that the car stalls when the end carb is covered does show a problem with that carb. Look closely at the casting and plate for any cracks.
I sure will! I'm thinking a worn shaft bore. Thanks for your help! Jim
Normally when you have a vacuum leak and cover the air horn of the carburetor the engine RPM will rise, due to the lean mixture created by the vacuum leak.
So by covering the air horn you richen the mixture up which raises the RPM.
Did you check the float level on that carb? If fuel poured out of the venturi I would suspect a high float level.
Joe
The problem is NOT with the front carb. Even at idle, there is flow through the secondary carbs. Completely choking either front or rear carb should cause the engine to stumble/stall and fuel to drip out of the boosters momentarily.
The problem is NOT with the front carb. Even at idle, there is flow through the secondary carbs. Completely choking either front or rear carb should cause the engine to stumble/stall and fuel to drip out of the boosters momentarily.
Thanks for your input. A couple carb shops tell me that at idle the only functioning carb is the center primary. The outside carbs are non functioning at idle. I tried to read your info. on tri power set-ups. unfortunately the print is so small it's hard to read. If your saying that it is normal for the engine to shutter and stall and gas to come out of the venturi, when I cover the front carb, then why do you think there is NO change when I cover the rear carb?
Am I correct that you are saying the front (secondary) carb is also assisting the engine with fuel at idle? Does the rear carb offer fuel too at idle? Very confusing!
The problem is NOT with the front carb. Even at idle, there is flow through the secondary carbs. Completely choking either front or rear carb should cause the engine to stumble/stall and fuel to drip out of the boosters momentarily.
Correct me if I'm wrong - but for clarity I think when you say there is flow through the secondary carbs at idle - you mean some air flow past the throttle blades and not fuel. Is that correct? I think most carb throttle blades - either secondary on a 4bbl or outboard carbs on tri-power, have their throttle blades slightly cracked open as a precaution against their sticking in the bores - which allows some air passage at idle.
"The outboard carburetors have a fixed idle system mentioned on the previous page. The fixed idle flow through very small idle passages in each outboard carburetor maintains good idle characteristics. This reduces the possibility of flooding from the outboard carburetors, and maintains a fresh fuel supply in both outboard carburetor fuel bowls."
In short, there is a non-adjustable idle circuit in both the outboard carbs. Covering the inlet to either outboard carb should cause a stumble at idle. The fact that covering the rear carb doesn't impact engine behavior tells me there is something amiss with that carb. I don't know how that is connected to your acceleration issue, though.
I would disconnect the linkage from the outboard carbs entirely and see if the issue persists. Some pictures of the carbs and linkage might help us to troubleshoot also.
"The outboard carburetors have a fixed idle system mentioned on the previous page. The fixed idle flow through very small idle passages in each outboard carburetor maintains good idle characteristics. This reduces the possibility of flooding from the outboard carburetors, and maintains a fresh fuel supply in both outboard carburetor fuel bowls."
Ah yes, "fresh fuel supply". Now that I read it, I remember that from another tri-power thread a few months ago. You probably posted that one too. I stand corrected.
Ah yes, "fresh fuel supply". Now that I read it, I remember that from another tri-power thread a few months ago. You probably posted that one too. I stand corrected.
This is the idle slot/hole in the 2300's base plate.
Thanks, I didn't realize what those slots did. So all three carbs offer fuel at idle? Guess it also helps to balance fuel distribution..
I'm away for a few days at Corvettes at Carlisle. Back on Sunday!!
This forum is very helpful
"The outboard carburetors have a fixed idle system mentioned on the previous page. The fixed idle flow through very small idle passages in each outboard carburetor maintains good idle characteristics. This reduces the possibility of flooding from the outboard carburetors, and maintains a fresh fuel supply in both outboard carburetor fuel bowls."
In short, there is a non-adjustable idle circuit in both the outboard carbs. Covering the inlet to either outboard carb should cause a stumble at idle. The fact that covering the rear carb doesn't impact engine behavior tells me there is something amiss with that carb. I don't know how that is connected to your acceleration issue, though.
I would disconnect the linkage from the outboard carbs entirely and see if the issue persists. Some pictures of the carbs and linkage might help us to troubleshoot also.
I will try your advise. But actually I think I need to shut off the vacuum source to the outside carb to shut it off (one at a time to test it). The linkage is only for shut down. I suppose I should also wire tie the throttle plate closed on the carb that is disconnected so it can't open with suction. Thanks for all your input..
Thanks, I didn't realize what those slots did. So all three carbs offer fuel at idle? Guess it also helps to balance fuel distribution..
I'm away for a few days at Corvettes at Carlisle. Back on Sunday!!
This forum is very helpful
Well - at least my miss-information can be informative.
Well - at least my miss-information can be informative.
All this information I have been getting is helpful an very appreciated! The forum is a great site when you hit the wall and need help. Thanks again.
Off to the Corvette show in Carlisle...
One of the diagrams shows an internal vacuum connection from the throttle bore of the secondary carbs to the diaphragms that actually open the secondaries. That is in addition to the vacuum lines from the primary carb that I thought was the only source of vacuum.
One of the diagrams shows an internal vacuum connection from the throttle bore of the secondary carbs to the diaphragms that actually open the secondaries. That is in addition to the vacuum lines from the primary carb that I thought was the only source of vacuum.
What is that for???
The secondary diaphragms are activated by venturi vacuum from the center carb, not by manifold vacuum; that operation is assisted by additional venturi vacuum signals from both end carburetors when they begin to open. Same operational theory as the venturi vacuum orifice in the secondary venturi in a vacuum-secondary Holley 4-barrel.
08-24-2016, 09:00 AM
