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Discussion Starter #1
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
 

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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
 

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Try cleaning out your distributor cap. Sometimes if you have some tracking or crud in it the spark can jump to another cylinder or just ground to the dist. Then try adjusting or replacing your points if you dont have electronic. Sounds like a definite spark issue.
 

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Next I would look at the plugs making sure all the same color, if you find one different color I would check that plug wire with a ohm tester and compare it with another wire or 2, if it different replace the wire
 

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Plug wires running too close to each other may cause "cross-fire". That is when the wire next to the one firing fires through induction at the same time. If you are running a high output ignition keep the wires an inch apart - at least.

Retarded ignition timing can also cause the exhaust to pop.
Make sure all the plugs are gapped the same; I found that my engines like a small gap (.030") Some have better luck with large gaps (.040" to .060")
 

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Discussion Starter #13
i had a tick that turned out to be one of my lifters, i think it maybe my plug wires, i started it last night and i didnt see any arking, compression tested at 160-65, plugs are golden brown, put a new rotor and distributer cap on today, seemed to smooth things out a bit. but it still going down the road at 1500-2000 and flooring it craps out and backfires through the carb, but ive checked my timing many times and its good, i think its mixed bag of problems
 

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i had this same problem my 600 holley carb.It' was not rebuilt, like i paid this guy to do.I fought this thing for a month.Everything was new,so i thought.I bought a new holley street avenger 670.Now it runs like a top.351c 4bbl eldelbrock torker intake,crane cam 272dur 524lift.Now i need to replace my FMX for a c6.Id say it's your carb.
 

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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?
 

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Now i need to replace my FMX for a c6.Id say it's your carb.
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.
 

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Discussion Starter #17
ok ive had it with this thing, i put a brand new carb on, new plug wires, cap, rotor, and coil. Timing is dead on, and its still idling ruff and popping through the exhaust. i dont know what else to do.
 

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I was having the same problem!
But it only happened when I had to lower my idle, because it was idling way to high!
The odd thing is that it happens after I let go of the gas going 65+. But I just saw one of my wires and it looks like it has a cut in it. Not sure how it happened but I gotta get it fixed asap!
 

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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?
 
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