[Murdawg]

The bane of my life Mustang will not give in. The car is horribly cursed and it is driving me insane. I am having an issue with it running lean and having a horrible off idle dead spot. Before I found that the distributor was bad and it had a total timing above 44 deg. So I ordered a new Petronix distributor. The first one I got the bottom of it where it goes into the box was not round and it would not fit in the motor. Then they where to overnight it to me and they forgot. Then it took me 4 sets of wires to get ones that will work.
Now after all that BS, I still have the same problem. The carb is a holley 600 with 64 jets which should be perfect for the car. I have taken the carb apart and everything looks fine. The floats are set right. The car will not run right until the secondaries open, and even then I think it is still not getting enough fuel.
The carb was supposed to be new. I took it part and looked at everything before I put it on the new motor. The renew kit I got as one through napa. In the kit there was not a lower gasket that was exactly the same. I checked it out and it looked like it would work. I guess I will order a Holley kit for it just to make sure. I did have some of the same problems on the old motor before I took the carb apart but not this bad.

 

[Explorer]

Off idle stumble is usually the accelerator pump. Vacuum advance set too high before advancing will cause it also. some have a allen head screw inside the spout to allow for adjustment. Just a couple things to ponder.

 

[Print Dad]

Hello Murdawg,
The issue is most likely in the carb because you had a problem with the other
motor.

Please don't take this the wrong way but I want to be sure - -

1. - Did you check the bowl heights with the site bowl screws on the side
of th carb?

2. - Have you adjusted the excellerator pump? To do this, you are supposed to tip carb over and set the gap between the lever and arn.
I find it works out pretty good with just a slight touch of the crew to the arm.

3. - Have you run a vacuum check on the motor?

Not sure if you mentioned if the carb is vacuum secondaries?

4. - When you apply the gas with the motor off - can you see a shot from the squirters? It should be almost a mist and not a heavy shot.

Would not hurt to rebuild the carb.

I think we can figure this out - - may take a few tries but we can fix this.

I hope you understand what I wrote - -it seems as though you can handle wrenched. If not - -please ask and I will explain my statements in finer detail.

Print Dad

 

[Murdawg]

I have checked the squirters, float level, ect. It idles fine and I have not been able to find any vacuum leaks. If you hold the throttle in a middle spot it is dead not just when you step on it but if you hold the throttle there. As soon as you give it enough gas to get the secondaries to open it comes out of it. They did send me a 4150 kit that I put in and the carb is a 4160. I am hoping that the small difference in the base plate gasket might take care of it. I have messed with a lot of holleys and never had this problem before. I have a 4160 kit coming on Monday and I am going to put that in. I pray it will solve my problem so I can do a final buff and wax, and I can give the car to the owner.
Thanks

 

[Murdawg]

So I just got a bran new Holley 600 for the car which should be almost perfect right out of the box. It is better but still not right. Now is has a much smaller light throttle bog but it is till there. I am going to go for another ride in it and see what the plugs look like after. The other problem it still has is if you jump on the throttle to quick it will fire out the intake. It has a bran new petronix distributor on it and the timing is set to 6 deg. All I want if or this clam to leave!!!!

 

[Murdawg]

So finding more out. The pcv is pulling a ton of vacuum. If I plug off the bottom of the pcv valve the rpm drops a good bit and the motor evens out. The pcv is connected to the spacer below the carb. It has a stock intake and the spacer plate came with the car. It has a formed rubber line that goes right to it. Why?

 

[Print Dad]

Hello Murdawg,
The first thing I would do is kick the timing up to 8 0r even 10 BTDC.

I think the car will run much better

The second part of this response deal with the PVC and hose.

I am not quite sure what you are asking.

The PCV is connected to the port on the base plate spacer to recycle the emissions from the PVC. In other words - the gases inside the motor rise up inside the head
and go through the PVC. They are then sent back into the motor and burned again.
This has to do with emissions and efficiency.

The reason you have a formed rubber line is so that the PCV will sit correctly and snuggly into the valve cover. If you just use a regular piece of hose, i could cause the PCV valve to lift or pull to the side a little and then the gas would escape and not get recycled.

Hope this helps.

Oh yeah - - on the carb issue. I really think advancing the timing will help with the bog. If not - - you may have to tweek the carb or the motor.
When we get new carbs - - they are supposed to be very close to set but they almost always need a fine tune.

Print Dad

 

[PaulS]

I suggest you replace the PCV valve. At idle it should almost shut off the vacuum. You will feel the vacuum when you plug it with your finger but it should not change the idle much. Does it hiss loudly when it is idling and you don't have it plugged?
They are cheap - replace it and see if that fixes the bog.
Other things to look at are:
timing - already mentioned
idle mixture adjustment
Idle speed
If it only has the flat spot when it is cold then adjust the choke.

 

[Murdawg]

So I have looked at it some more without figuring it out. Did some more checking though. I changed out the PCV. I re adjusted the mixture screw and I am still having the same problem. I got it so that at idle it runs rather smooth and I get a steady 16 on the vacuum gauge. As soon as a crack the throttle open a little the vacuum gauge starts to bounce up and down between 15 and 16. You can also hear that it is not running 100%. This is also where I have the running problem.
The squirters are fine the carb is new. When you hold it in that low throttle position is where it has a problem.

 

[Murdawg]

Going to try and do something to this POS today. I really just want to burn it or run it over with my big truck. I got rid of one POS Ford yesterday hoping to get the other one gone this week two.

 

[PaulS]

Sounds like the idle feed restriction needs to be opened up. That kind of tuning is normally restricted to road race fanatics who, like me, want a carb that runs silky smooth on and between all circuits. It will be better to use a genuine Holley kit and genuine Holley parts when working on it. That way the parts you get and the instructions provided will be correct for the carb that you have. I wonder if the gasket(s) you used are leaking vacuum into the idle circuit.

 

[Murdawg]

The carb that is on it now is bran new and I have done nothing to it besides adjust the idle screws. The carb should be almost dead nuts on right out of the box so I am a little confused. I was thinking today about maybe trying to set the idle screws with the throttle in the dead spot to see if that will help.
What should the plugs look like? I like to see a plug with some color. The plugs I am taking out of this are white white. Someone told me that on the gas today you won't get much color on a plug. How much color should one get on a plug. On my race snowmobiles I have them so I have a uniform light chocolate brown.