[Stang-289]

My 66 has been running roughly since I had done a few things that you wouldn't think would do anything but..

These are ALL the things I've done to it prior to it running roughly. Given, it was not perfect before but now it needs a higher idle to stay running and something sounds different.

-change oil
-change oil filter
-change air filter
-added lead additive to fuel
-changed fuel filter

I'm no mechanic by any means but If I had to guess it would be the lead additive. I was told that this specific engine needs it to run properly but I'm not so sure.

If you would like any more info and pictures,video. Just say so.

Thanks,

Stang-289

[19coupe66]

8 cylinder ?
you may need a fresh set of points, plugs, wires, cap and rotor, thats where i would start. if you have never set points learn BEFORE you change them. good luck

[19coupe66]

as for the lead additive, i ran my 63 mercury for 5 years and now my 66 mustang, both 6 cylinders without any lead additives. they both run great so long as the points are set right, the plugs are clean and the carb is adjusted properly.