350 runs rough

[newfdude]

hi guys my 350 runs rough when put in gear checked timing its set at 8 degrees idles at a 1000 rpm fairly smooth i put a vacuum gauge on it it flucuates rapidly between 10 and 15 hgs it has a 650 holley dp new plugs and wires cap rotor button any help would be great frusterated

[MagicRat]

If the camshaft is stock or near stock, that vacuum reading is pretty low. You may have leaking intake valves, a vacuum leak or late timing.

Try advancing the timing 2 degrees at a time and see if the roughness improves. Beware of hard starting, detonation or a spark knock. If you hear one, or the engine does not start easily, you have advanced things a bit too far.

[Bad81bu]

Would the rapid fluxuation of the vaccuum possibly be something as simple as a vaccuum leak, perhaps at the carb gasket?? try spraying carb cleaner all around the base of the carb and where other vaccuum leaks may occur, if it idles up or changes in any way then poof theres the problem. I like to go the cheap diagnosis route first.
Hope it helps
Brett.

[MrPbody]

Generally, when the vacuum guage fluctuates, an intake valve is either "weak" or bent (POSSIBLY "burned", but intakes rarely burn). A cylinder leakage or "leak down" test is called for. A static compression test MAY spot it.

Jim

[newfdude]

thanks guys did a compression test found #4 and #7 low 40 psi and 7opsi thanks