[fonzie65]

hey i have a 1965 mustang with a 289 2 barrel. it's been sitting a long time but me and my dad got it started. it idles fine and if you floor it it revs fine, the problem is it has no mid range power. if you give it half throttle it runs bad and acts like it wants to turn off. anyone know what it could be?

[Bob A]

Try changing your fuel filter, if not you said the cars been sitting awhile you might have a bad accelerator pump in your carb. It maybe time to have it rebuilt. Good Luck

[paul289]

Usually, a flat spot means the ignition timing is off, there's a vacuum leak, or the carb isn't tuned right. It's probably the carburetor, so it likely needs a rebuild.

[fonzie65]

thanks it was a vaccum issue. thanks for the help.
Fonzie65

[bbianco]

If it works well at full throttle with no hesitation, the accel pump is probably OK. Check the ignition timing, 10-12 degrees usually works well for a 289. Make sure to check the timing at idle with the vacuum advance hose off. The increase the speed to about 3000 rpm and make sure the timing advances properly. If it doesn,t, the distributor shaft and advance may be gummed up. If it advances OK, the make sure the vacuum hose has vacuum on it and reattach it. When you reattach, the timing should jump 10 degrees or more. If it doesn,t then the vacuum advance unit is leaking and will need to re placed. If the cavuum hose to the advance has no vacuum, make sure it is riouted to the correct place on the manifold and that the rubber hose on the manifold end is in good condition.