[blakesmustang]

hey guys,
i have a 66 mustang with a 351W. and i just got the car running again. before i pulled the engine the car would stutter and it died at stop lights if i wasnt on the gas. so i got it started today and drove it around,the tac would wobble and fluctuate at idlem and when i would let off the clutch and give it gas it would stutter until i got up to about 15-20mph. what would cause this? valve adjustments? and also when i would go to start the car i would turn the key and nothing would happen (no click) and the 2nd time id turn the key the car would start. weird seeing that i replaced all the battery cables yesterday. could this be the solenoid? and all of my electrics would work when the key was in the on position...
any help would be appreciated!!

 

[a228380]

i would use a vacuum gauge to diagnose the stutter and stall problems. a good site for a tutorial is How to Use and Interpret a Vacuum Gauge

 

[dklistul]

Hmmmmm. Lessee here.

Could be ignition. Wires, plugs, cap, rotor. Pretty cheap to replace.

Could be carburetion. Idle mix wrong, off-idle circuit clogged, power valve blown (does it put out a lot of black smoke?).

Could be vacuum leaks. Carburetor throttle shaft bores worn, intake manifold leaks, vacuum line leaks (that's what I'd look for first), etc.

Could be leaking valves. A compression check can help diagnose this.

Could be a worn out motor (probably not the cause here, but who knows???)

Probably NOT valve adjustment, unless someone has put mechanical lifters into your motor. Does it make lots of valve clatter? If not, look elsewhere.

Just way too little info to work with. Tell us what you've done to it since it last ran properly. What does the exhaust look and smell like (no, don't stick your face directly into the tailpipe. gringreen) Does the motor make any unusual mechanical noises?

My first thought is a vacuum leak. As stated above, get that vacuum gauge hooked up and tell us what it shows. More than the number, too. Tell us whether it's steady at idle or if it oscillates up and down. If the idle speed is unstable, you'll probably see the needle fluctuate a bit with the idle speed.

Test. Don't guess. Vacuum test, compression test. And if required in your area, an emissions test report can tell you a LOT about the motor.

 

[rex1965]

You may have multiple problems:

1. For the no crank problem. Check the ground wire on the back of the passenger side head to the firewall. Also check the battery cables and connections, solonoid connections, and the connection of the starter. Other possibilities are (neutral safety switch if an automatic) or a maybe a switch on the clutch pedal if a manual trans, or the ignition switch. A voltmeter or even a test light would prove helpful in finding where the voltage is missing.

2. For the shudder and stalling when slowing down, if the engine runs okay under load (accelerating), then it is getting gas and most likely the ignition is performing okay, then I would look for vacuum leaks, check the initial ignition timing, check the float level, and the idle mixture and speed adjustment, automatics usually have a dashpot on the carb, this slows the throttle closing when letting off the gas so the engine doesn't die. If it is shuddering under acceleration, then you have an ignition problem, bad valves, or severe compression loss on some cylinders, and possibly fuel related problems, the spark plug wires are not in the correct firing order for your engine, 351 is different from a 302, unless it has a 302 camshaft installed.

Post your results. Good Luck.

 

[blakesmustang]

Hmm well the motor has about 1500 miles on it, and before we pulled the motor we had it running rich, that's the only way it'd run, so i guess it hasnt run 100% properly yet haha and im
Only 16 so i dont know exactly what to look for just yet. I did make adjustments to the carb to make it run a bit leaner. And the Carb is new, the intake gasket is new, and when ever I plug up the power brake booster hole (engine side...) same problem and i also checked for leaks with the carb (used wd 40) and the vaccume seemed fine. The distributor is new pertronix, and that helped the problem, I had points in it before and the car would run 10x worse than it does now. And the car doesn't smoke
At all. And if I adjust the carb to get it to run right what exhaust smell should I be looking for? And the only weird noise is a valve tick from cylinder 4 I haven't adjusted it yet, but it made the same noise before I pulled the motor. And where can I get a vaccume tester?

 

[blakesmustang]

Oh and thanks for the comments guys I'm definatley going to look
At all of the options and suggestions:bigthumbsup

 

[blakesmustang]

Also my timing is way off! Its suppose to run at about 6 degrease but the timing light shows the mark to
Be almost at the top of the harmonic balancer. I checked the timing chain and gears to see if they were off, but they were right on. And the distributor isnt 180 or a tooth off

 

[dklistul]

What carb do you have? 2 or 4 barrel? Who made it? Ford? Autolite? Holley? Carter? Edelbrock? Don't overlook the obvious. Someone hasn't installed a single-plane 4-barrel manifold on a grocery-getter, have they?

And what exactly did you do to it to "make it run a bit leaner"? Jet changes? Metering rod changes? Idle screw adjustments? On some carbs, the idle screws are fuel metering needles, others are air-bleed screws. They work backwards from each other.

A vacuum gauge can be found at Sears, Harbor Freight, Auto Zone, O'Reilley's, etc. Basically, most places that sell automotive tools. Probably less than $20, though I haven't bought one in years so I might be a bit off on that price. Good to have in your toolbox, though.

If the mix has to be rich to make the car run, it could be telling you that your spark is weak (a rich mixture is much easier to light than a stoichiometric or lean mix). Causes of weak spark include (in no particular order): low voltage at the coil, crappy points, bad condenser, poor ground of the engine to frame, bad wires, weak coil, + (bat) and - (dist) wires connected backwards on the coil (common mistake - yes, it makes a HUGE difference and correcting this has made a LOT of cars run great), and probably a few that my tired old just brain isn't letting go of tonight.

As I said in another post, one thing I've learned over the years (I've been bending wrenches since 1968) is that 90% of your fuel problems are ignition related - especially on non-computerized, carbureted, breaker-point ignition engines.

One more thing. Over the years, the harmonic balancer can degrade. The outcome of this is that outer part moves on the rubber, the result being that the timing mark isn't in the right place any more. If you're not having any kicking back during engine start, or any detonation or spark knock problems, I wouldn't suspect or worry too much about timing just yet.

 

[blakesmustang]

That carb is edelbrock and to make it run leaner there are 2 idle
Mixture screws on the front of the carb screw out to make the mixture lean screw in for a richer mixture. I unscrewed 2 1/2 turns.

 

[blakesmustang]

4 1/2 (not 2 1/2 typo sorry haha tired) turns from where it was running before

 

[dklistul]

OK. A new carburetor. This could be a clue.

I'm going to assume that the 351 is essentially stock. That is, a stock or mildly upgraded cam, stock heads, factory compression ratio, etc.

Which Edelbrock? Do you have a number on it? Like 1404, 1406, 1407, etc? I'm assuming it's a vacuum secondary, carb. If you're running a 750 CFM carb, it's too big. Velocity through the venturis is too slow to provide a good signal to the rest of the control circuits.

Living most of my life in Colorado, I've learned to spot a carbureted car a long way off, especially in the mountains. A carbureted car will nearly always belch black smoke while pulling the grades to the passes because the car effectively has too much carburetor as the altitude increases. Less venturi signal to control the metering circuits leaves the mixture very rich and the result is very visible. Looks like you're in Texas so altitude isn't the problem, but the basics still apply.

You have the logic right on the idle screws. They're air bleed screws on an Edelbrock so OUT is LEAN. But you also said that you had to make it rich to make it run, so I'm a little confused here.

Based on what you've said so far, and assuming it's NOT over-carbureted, I'm still leaning toward either a vacuum leak somewhere or ignition trouble, and I think I'd start with the ignition if there are no obvious vacuum leaks. But check all the hoses over closely with a bright light, flex them all as best you can while the engine is running and listen for any changes in idle speed or obvious hisssssssssssssing sound.

Do you have power brakes? If so, do they work OK?

When I mentioned exhaust smell, I was referring to the smell it gives when it's running overly rich. Another clue of this is lots of soot in the tailpipe.

I'm actually in Houston right now on business and won't be able to look at this thread again until tomorrow night when I get home, but keep us posted on what you find (or don't find).

 

[blakesmustang]

Hey guys sorry for responding so late, but we think that my power brake booster hose was leaking and that caused the stuttering. I still have a small stutter whenever Im driving at a constant speed and I step
On the gas to get going a little faster

 

[blakesmustang]

Oh and the carb is a 600cfm and I don't have the part ##

 

[jay_pearce]

I vote vacuum leak. Not sure if anyone else has tried this or not but an old farmer had me take an acetylene torch and SLOWLY bleed acetylene out the tip while moving from vacuum connection to vacuum connection.... when the engine speeds up your getting warmer ;-) worked like a charm. found a ruptured secondary diaphragm that was causing mine to run just like you are describing. i would assume that a propane or map gas torch would work just about as well. Just a thought...

 

[blakesmustang]

Well now the car won't run right at all. At idle it runs extremely rough and the tach fluctuates violently at any rpm. It happened today. I was driving and heard a horrible ticking so I pulled over and determined one of my valve nuts came loose. I was close to home so I got it home ok and pulled a valve cover to tighten the nut. Once it was tightened (not too tight just about as tight as the others) and i started it and it's been acting up since. My timing issue did get better be cause the mark was closer to where it should've been, but the timing light showed that cylinder 1 was not firing all the time at idle...im not sure it's vaccume any more.

 

[blakesmustang]

The valves were adjusted yesterday. It's a hydraulic cam, with hydraulic lifters and the whole 9 yards. And it was cylinder 1's exhaust valve that came loose

 

[blakesmustang]

It is also just now deciding to kick back and run backwards