gassy spark plugs

[amaterasu71]

Hi everyone, So bought 73 mach one with q code 351 cleveland. She had been sitting (less than a 1k in ten years and 2k over the past 20 after a rebuild) and idle was rough so brought it in. My mechanic told me he changed thermostat and took off bowls and rejetted carbs as they were dirty. So it now is kind of herky jerky when it comes to throttle response best described as it seems to load op on fuel then take off. I changed out the plugs tonight and discovered each plug smelled of gas/oil and were slick to the touch. So i think it is running rich? what should I do? thanks again...

 

[kcmash]

Ask your mechanic what he did when he "re-Jetted" the carb.  Did he tell you what size he took out and what size he put in?

How does the car do at idle?  Black smoke?  Stings your eyes?

I am assuming you have a Holley carb.  Did your mechanic do a idle adjustment with a vacuum gage to optimize the idle mixture?  Also, what RPM do you idle at?

Sounds to me like you are loading up at idle(too much gas) causing muddy takeoffs.  Let me know the answers from above and a few of us can chime in for the best things to try from here.

kcmash

 

[Don C]

Not sure why he would have changed the jets. Did he put in a complete rebuild kit? New power valve and accelerator pump diaphragm, new float needles and seats and adjust float level, new check valves (balls), new gaskets, thorough cleaning?

Yes, it sounds like it is either running rich or an ignition problem isn't burning the fuel.

 

[OzCoupe72]

Sounds like flooding and due to the fact it has been sitting around for a while the needle & seats are probably sticky

Perhaps just replace them and readjust your float levels

What carby is on it? Maybe others can give some tuning tips?

 

[MustangNJ]

when I bought my 73 mach 1 in the Spring, it had been unused for the better part of 10 years. It would start, but would not idle. when driving, the motor was surging badly. the biggest problem was 10yrs of ethanol residue in the carb, so I cleaned in completely. there was also a problem with the fuel sending unit, so I replaced it and the fuel filter which was a mess. that solved the idle and surging problem. very smooth now. I have not looked at the plugs, but that is on the list for this weekend.

 

[delawarebill]

been a long time without new plugs.. yes replace, add high test fuel, and a bottle of cleaner in gas tk, change oil and filter and take out for a hard run.. it needs it. a car just sitting for years and not put away correctly is bad news and much can happen over time..

get the stang running and come to the "delaware park casino car show" it's sept and can't remember the date.. but it brings about 800 cars. it's called "gears and beers"

 

[SteveO_71]

When the mechanic changed the thermostat, you may want to doublecheck if he was aware of the proper thermostat to use in the Cleveland. The one that properly blocks off the bypass so as to not get overheating issues. One less thing to worry about.

 

[Carolina_Mountain_Mustangs]

You should also change all the rubber gas lines to ethanol resistant. If old they are not. Use the fuel injecting type clamps on the lines has smooth surface not like the toothed clamps. Hose back at the tank pick up, going through the inner fender under the master cylinder. Going to the fuel pump then at the carburetor. If the mechanic did not change the rubber parts in the carb they are probably the old non ethanol type and can cause issue also.

I run ethanol free 90 91 octane fuel in my 351 C and add the Lucas gas treatment that replaces the lead. I have gone through probably 6 tanks of fuel this summer and runs great except for my vacuum leak in the brake booster. 

I would also be suspect of the thermostat. He might have done something wrong. They do have the right ones at the parts houses just has to have the post or hat in the center of the thermostat to go into the baffle in the block. I would run a 192 deg..

Here is pic of a couple of the correct styles. I have sold all of the ones I had found in old parts house. I do know they have them at Advance I had them pull one and looked at it.

 

[amaterasu71]

Thanks guys I will let you know what i find out from mechanic today your knowledge is appreciated...

 

[Stanglover]

Run a part bottle of "Sea Foam" through the carb and add the appropriate amount to a fresh tank of fuel. That stuff works wonders. Not cheap, but worth it.

Check your timing too. the amount of initial timing depends on your total mechanical advance which should be around 34 - 36 degrees @ 3000 rpm, vac lines plugged. I'm not too sure about the 73's timing requirements, others will advise I'm sure. If the timing is too far retarded, your idle will be affected. What distributor do you have on that bad boy?

 

[amaterasu71]

so when it was in the mechanic did the following..clean front and rear fuel bowls, replaced needle and seat o rings, replaced bad power valve adjusted fuel bowls levels as needed,adjusted idle mixture screws adjusted ignition timing..... he also replaced the thermostat (ive ordered a tmeyer with the correct thermostat) which is working ok... after talking with him he said to bring it in and he would look at it to determine what is up with the issues im having......ill keep you updated ...

 

[amaterasu71]

So I just ran a bottle of seafoam through the carb and changed the fuel filter, this did seem to improve the issues. Part of the problem is my inexperience when it comes to driving a old classic with a v8. Not sure what i should be expecting for power but it does seem to be running smoother and i will have my guy take it for a spin to see if it needs further attention thanks for the help and i will keep you all informed...