Still having acceleration issues:

[TheDude]

**1968 200ci engine with Pacemaker dual outlet header, dual exhaust, Holley 5200 2bbl carb, Pertronix electronic ignition**

Hi,

I was able to take the Mustang to my old high school for a show today, and as usual, it stumbled when accelerating. It does not seem to do it as bad in the higher RPM range. A few minutes into the drive home, the engine did not stumble much at all but not all of the power was there. It does not seem like that would be a timing issue. If it was, wouldn't the problem be continuous? I just redid the carburetor and carburetor adapter mounting gaskets, and this time I used gasket sealer. I thought that might haved solved the problem if it was a vacuum leak. No good. I have my spark plugs gapped to .050", which is what many I6ers run them at, correct?

What are your thoughts on it being the accelerator pump?

Thank you,

Justin

P.S. I have four (yes, four ) pretty girls who want a ride in the Mustang but I cannot do that with such poor performance.

 

[Junk-Falcon]

it

 

[MustangSix]

I would investigate the timing again. Too many people are too quick to jump to carburetion as the cause of their problems before completely checking out the sparks.

Always, always, always check the ignition and timing first. Poor acceleration and the symptoms you describe could be caused by timing or poor plug wires, both of which could be easily checked and ruled out before tearing into the carb.

Try advancing the timing a little. rotate the distributor counter clock just a bit and see if the symptoms go away. Make sure the wires aren't arcing at higher rpm. Mist the wires with water to see if you can replicate the problem when not under load. Try gapping the plugs back to .035". If the gap is too wide, you could be arcing somewhere else.

 

[CobraSix]

I agree with Jack, rule out timing and ignition first. Those issues are not always consistent. I've been of the forums for awhile, so when is the last time you check TDC mark on your pulley? Make sure its right.

Make sure you are getting good spark on all the wires. I was having a similar problem (not exact) and I ended up have a wire's cover cracked (New wires too) that was arcing across to the fuel pump filter housing on my early style fuel pump at lower RPMs.

Slade

 

[Lazy JW]

....
Always, always, always check the ignition and timing first...

Yup. No amount of carburetion wizardry will cure an ignition problem. We went through this at length with Cfmustang, turned out it was his carb but it was easy to prove once the ignition was dialed in. He did have serious timing issues at first, including overheating.
Joe

 

[TheDude]

Thanks for the help so far. I increased the timing and did a test drive. I increased it by a small amount each time. That did not help.

The stumbling problem occurs whenever it wants to, unlike I siad in my first post. It happens all across the RPM range.

it sounds lean , weather its the mix or exl pump , i would try the screw another 1/4 to 1/3 out n see if that makes any diff , look at the plugs after a good ride then look after ya richen it ,
just a cheep thing to try , it could be the pump isnt pumping enoff of a squirt , but thats a linkage thing aint it?

Are you referring to the air mixture screw?

MustangSix, if I mist the spark plug wires, what exactly am I looking for?

Thanks

 

[JackFish]

I'll throw something out here. Had a slight hesitating at rpm, a small stumble.
Tracked it down to a vacuum line that had become loose in its boot. In this case it was at the distributor. It has tape on it now.
Of course, last night I had to go and melt the line to the egr...

 

[hasa68mustang]

Thanks for the help so far. I increased the timing and did a test drive. I increased it by a small amount each time. That did not help.

The stumbling problem occurs whenever it wants to, unlike I siad in my first post. It happens all across the RPM range.

it sounds lean , weather its the mix or exl pump , i would try the screw another 1/4 to 1/3 out n see if that makes any diff , look at the plugs after a good ride then look after ya richen it ,
just a cheep thing to try , it could be the pump isnt pumping enoff of a squirt , but thats a linkage thing aint it?

Are you referring to the air mixture screw?

MustangSix, if I mist the spark plug wires, what exactly am I looking for?

Thanks

I believe you are looking for it to start stumbling and not running smooth

 

[MustangSix]

Any misfire caused by leakage in a wire will be much worse when they are damp. Often you can see or hear the bad wire if it is arcing somewhere.

did you regap the plugs to something smaller?

 

[cfmustang]

Yup.

I had both timing and carburation issues, but would never have been able to sort out the carb issues till the timing was sorted out first!

 

[Anonymous]

i also would suggest reduceing plug gap. .050 is kinda large for a stock coil. I have seen plugs get way hot with a too large gap resulting in terrible performance. To run that much gap everything must be in perfect shape and able to cope with that much resistance. Sounds as much like weak ign. as anything else and more fuel will sometimes mask a certain amount of problem especially in a cold engine. but unless you're at Madi Gras a mask doesn't cure acne ( wow that was wierd even for me)

 

[Guest]

Idle air screw and choke. The choke should be properly tuned, if its not, youll either run lean or rich, in either case, sounds like some of the symptoms. Loss at acceleration. Youre probably puffing out a black cloud of raw fuel (rich) every time you step on it, cause the flap on the choke aint lettin' enough air in.

Condition: rich A/F ratio. Too rich=bad acceleration, low fuel economy. etc.

Idle air screw adjustment: with car off, turn the idle air screw in ALL the way, then unscrew it 1 1/2 turns. Start the car, and fine tune it to your ear. Youll hear the sweet spot

Choke: With car engine cold and car started, unscrew the wire connecting the choke pull knob to the choke. Move the choke flap very little while its at idle until you feel it is properly idling, open to closed. Move it here, hold and listen, move it there, hold and listen, until its idling correctly. Youll hear the sweet spot. Then just tighten down the screw.

Do the choke AFTER the idle air screw. Works better that way, because 1 1/2 turns is a reference.

Either that, or your float is bad, but you said you rebuilt it?

 

[TheDude]

Great, thanks for the information everyone.

The carburetor is a rebuilt unit I bought from Stovebolt. I should have mentioned that I have a Flamethrower coil and Pertronix electronic ignition. I ran .05" plug gaps with the previous 2bbl carb with no problems. It could very possibly be the air idle screw, I do not think I ever had it properly adjusted.

Thanks

 

[TheDude]

Who's whistling?

Now I have a whistling sound coming from what seems like the carburetor. This happened before but it went away...any ideas?


The engine would turn over but not stay running with the air mixture screw only backed out 1 1/2, or even several turns. I think I have it idling smoothly now but I shut the engine off because of the whistling. The Mustang is blocked in by the other cars and it is almost time for dinner, so I will have to do a test drive tomorrow evening.

 

[Anonymous]

the whistling sounds like a vacuum leak to me...it might be on the carb itself not between the base and manifold...get some sort of spray and spray down the carb with the car running....if u spray over the leak the whistle should temporarily go away and the engine will run like it should. only other time i had a whisle was when i bored out a venturi on a carb and made a new one lower down just for fun...it didnt work so i chucked it, lol.

 

[kspageddie]

I had a whistling noise too. I rebuilt my carb and the noise went away and the car ran like a champ. Just thought I would throw that out there

 

[TheDude]

Ha! Take that, carburetor.

I made some adjustments to the air mixture screw. It runs much better now. I can spin the tires quite well from a standstill. When I accelerate from 1500-2000 RPM, or around 30mph, I can feel a loss of power. Maybe it happens when the secondary valve opens up...I will have to do some more test drives.

Basically, the air mixture screw is solving the problem.

Looks like I can drive the Mustang to work tomorrow.

 

[Guest]

Line up the babes you got wanting a ride.

Then get a picture of all of them cruising with you.

That WILL work dude. At least that helped so far. Sounds like you have a slight float problem too, but not sure.