Having problems with your 1965 Ford Mustang ?
I have a newly rebuilt engine (289, 4bl) with a Demon carburetor (Road Demon Jr. / 525 cfm). The engine idles, and at strong acceleration runs fine. When I try to moderately accelerate or try to maintain speed when going up an incline, it stumbles as if being buffeted by the wind. I have exchange the squirters from a 32 to a 35 with no effect. The carburetor sits on a 4'' high rise manifold and the engine has a cam that is slightly bigger than stock. Timing is between 12-14 degrees advanced
Your problem would be in the power valve/accelerator pump circuit. This is the circuit that feeds gas to the engine when the changeover from idle to driving occurs.At idle the vacuum in the carb draws gas so no mechanical means of delivering fuel is needed. The same is true when you reach a consistant driving speed.During the changeover you need a way to increase fuel to the engine by mechanical means. Some carbs have an accelerator pump some call it a power valve. The changes in your intake and cam are enough so the stock circuit is unable to compensate properly. The dealer for the carb should be able to help you out with parts to increase the flow and rate of flow. Hope this helps.
Repair Help & Product Troubleshooting for 1965 Ford Mustang
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