I have been trying to get my 65 mustang to run for awhile now. It was previously sitting for 20 years before I bought it about 3 weeks ago. The engine was supposedly rebuilt before it was sitting and the carb was also supposedly rebuild right before I bought it. The transmission was all screwed up so I just put in a rebuilt C4.

Anyways, the car isnt holding an idle very well. I believe it is the carb. When I manually adjust the flap it makes a big difference in how it runs. Even if I barely touch the flap. I can also screw one of the idle screws all the way down and it doesnt really effect how it runs. The other idle screw is barely unscrewed and that seems to make it run the best for some reason.

I am getting fuel and spark no problem. I replaced all the plugs and the entire fuel system from the sending unit, tank, lines, and fuel pump.

It sounds like there might be a vacuum leak? The port on the manifold goes down to the transmission and its all hooked up well. The PCV valve looks brand new and I manually closed it and it did not effect how it ran. The vacuum advance is hooked up correctly and I believe its working fine. Where else should I check for vacuum leaks or do you have any other suggestions?

 

you can check for vacuum leaks sparaying it down. get a carb cleaner spray and spray that with engine running along the intake manifold, the carb base, the carb itself etc. everywhere but inside the carb. if idle changes you have a leak where you're spraying

if you have power assisted brakes disconnect that for a quick test as well (don't forget to put back on). if the diaphragm in there is gone that could be a problem.

however if you can screw in one til stop without the engine cutting out i'd say it's running too rich or something in the carb is blocked already, check if you can see petrol pouring in the carb while running. if you do that's a problem.

i guess with the flap you mean the choke butterfly. when warm it has to be fully open

 

On a motor thats sat for 20 years i would suggest a compression test. You can rebuild the carb 20 times but if you have a dead cylinder then it wont do any good.

Once you know the motor is good then its time to look at what else is going on. Start with spraying carb cleaner around the intake and base of the carb. If there is a spot that the RPMs increase then thats your vaccum leak. If you have power brakes disconnect the line off the booster and plug it to see if that helps.

Next take the fuel line off the carb and disconnect the coil wire. shove some rubber fuel line onto the end of the hose and stick the other end into a clean and empty soda bottle(clear plastic). crank the motor and get a sample of the fuel. Just keep safety inmind that you dont make sparks, spray gas or start a fire. You are looking for water or particles. After sitting for 20 years its likely you have something funky in the tank or lines. You need to get this sorted out before rebuilding the carb or your just going to put the crud right back into the fresh carb.

After you know you have a solid fuel system, no vaccum leaks and a solid motor then i would buy a kit for the carb and rebuild it. 20 year old gaskets leak. 20 year old needle valve rubber doesnt seal. Also i bet that when you open the carb up you will see build up and crud in the bowl of the carb and in the passages.

 

Already did a compression test and the engine is good. Also I replaced the whole fuel system so I know I am getting good fuel. The carb is also supposedly rebuilt.

Ill try the carb cleaner

 

any other suggestions I should try other than the carb cleaner? Could it be something other than a vacuum leak?

 

you can use WD40 as well. about anything that sprays and doesn't leave marks.
as said before, if you can screw in one side idle screw i have my money on either something in the carb is blocked/dirty. or you're poring fuel where you shouldn't. check with choke open if you can see gas anywhere in the carb. if you can see gas something is wrong with the carb or float levels. was the carb rebuilt before you cleaned out all the fuel system, if yes it might just have gone dirty again.

 

I bought some carb cleaner and did the test and nothing improved the idle. I also set the screws correctly and it didnt seem to help the idle much but I was able to get the car in gear and drive it around.

I have 2 problems now

1. When I drove the car it was very sluggish almost like I had a heavy trailer attached to the back. I would floor the gas pedal and the car wouldnt go anywhere. It was almost as if it was riding the brakes. I should check the brakes but I dont think it was that. The vacuum advance might not be working in the distributor end but would that have an affect like this?

2. The engine is running pretty rough. I adjusted the timing and tinkered with the carb more and cant get it to run well. I did a compression check earlier and it was good. I just checked the valves and noticed that they were all pretty loose. I tightened the rockers down until they touched the springs without being able to lift them up or rock them very much back and forth, then tightened them 1/2 turn. I did this to all of them and they all needed at least a full turn. Could these loose valves cause the car to run rough?

I will run the car again tomorrow. Its late and I am probably pissing my neighbors off with these open headers haha

 

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I bought some carb cleaner and did the test and nothing improved the idle. I also set the screws correctly and it didnt seem to help the idle much but I was able to get the car in gear and drive it around.

I have 2 problems now

1. When I drove the car it was very sluggish almost like I had a heavy trailer attached to the back.

---> put the car in neutrtal handbrake off and push it forward and backward. then you'll know if you have locked brakes. or just lift everyu wheel one by one and spin it


2. I tightened the rockers down until they touched the springs without being able to lift them up or rock them very much back and forth, then tightened them 1/2 turn.

loose valves can cause car to run rough but you will hear that as a valve ticking. if you adjusted them by just turning then you did that wrong (don't run that way).
what you need to do if you have hydraulic lifters is to:

turn the engine to TDC with a rachet and socket at crank. turn clockwise
- keep turning until the exhaust valve of #1 cylinder just starts to open, the pushrod will go up. (here we are guaranteed that #1 intake valve is closed)
- now you can adjust the #1 intake valve: open the rocker until you can move the intake pushrod up and down, close slowly until you can't move the pushrod up and down anymore. you'll feel as well that you can't turn the pushrod anymore. that's zero lash. close by another quarter to half turn.

check on your firing order which cylinder will come next.
in case you have 1-3-7 ... it will be number 3, but check first!

let's say it is #3, then you keep turning until #3 exhaust just opens. now you can adjust #3 intake valve as above. do that for the full firing order (2 full engine turns).

Once you are done with that it's time to adjust the exhaust valves . for this keep turning until intake valve just closes (turn til you see it opening, when youkeep turning it will start to close again. that's where you can adjust exhaust #1). keep doing so for the rest of the firing order.

A good practise is to write the firing order down twice and cross out what you have adjusted. further doubel make sure that you are looking at the correct valve to go up or down, as well that you adjust the correct valve.

if you just used your rachet across all valves without turning engine it was done wrong.

 

I did adjust them that way just not in that order. It did it the quick ghetto way and tightened all the ones that looked like the valves wernt open, then turned the engine a little and checked again. I did that 4-5 times on each side. Even if I accidentally tightened a valve that was open a little, the rocker should be able to move at some point when I was rotating the engine (when the valve was completely closed). But I checked several times and they were all tight in the end.

 

Ok one thing that i am confused with is the fact that you touch the "flapper" and it runs better. Correct me if i am wrong but i am assuming you are talking about the choke plate on the top of the carb. Is it that you close the choke or open it that it runs better? If you lay your hand over one of the barrels does it run better(running lean) or does it die(running rich)?