Ford Mustang Forum banner

351 cleveland not running correctly

12668 21
ok i have a 351c that i cant get to run right, it idles really ruff under 1000 rpms, then when you take it up to 2 or 3 and hold it there it pops through the exhaust every few seconds. any help would be awesome thanks guys.-Eric
1 - 5 of 5 Posts
Not alot of information to go on here but it sounds like a typical case of needing a tune up and a carb rebuilt/adjustment

If you have not done a tune up in the last couple years I would put in:

Cap
Wires
Points
Coil
Pull the plugs and check to see if you are running lean or fat, put in new plugs
Check timing confirm it is still set to stock specs (if you have a stock cam)
Check carb float levels and adjust the idle air/fuel settings until you get the car it idle where you want it.

I have generally found when I am popping out my exhaust it is because I am not getting full spark in one or more cylinders that traces back to the ignition system in 1 way or the other...in my case it is usually a stupid wire is not completely on one of the spark plugs.

I have a 410 Cleveland with a decent sized cam that runs 11.45 in the 1/4 through an AOD on 17s...and it idles at 700-750 or so RPM so even if you have a larger than stock cam you should be able to idle well below 1000 RPM.

YouTube - Fixed the header leak again....first start
So now that you have new cap/rotor, what is your initial timing set at? What is the total advance? When is it all in by?

If all that passes muster then turn your attention to the carb, if you floor it and it bogs your power valve could be shot, is it a vacuum or mechanical secondary carb...what spring is on it?
Out of curiosity why on earth would you do this? Both of these transmission are huge power stealers. If you are going to spend time and effort changing a transmission it should be (IMO) either to put a much lighter c4 in or an AOD to get you an over drive benefit. There is nothing deficient about an FMX behind a 351c.
Now i need to replace my FMX for a c6.Id say it's your carb.
Well you are eliminating problems. So if you changed the plugs, wires, points, coil, cap, rotor, etc...and it was all installed and gapped correct, wires in the right order, and the timing is adjusted properly now you need:

I would say check the carb and confirm it is operating properly, doesn't have a blown power valve, floats are set, air bleeds are set right, etc...but you claim you put a new carb on. Out of the box new?

If the problem remains then you pull a valve cover and check to make sure all your rockers are still connected, make sure you don't have a collapsed lifter.

What is initial advance, what is your total, and what RPM is it all in by?
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top