200 idle

S

stangman196700

Active member
OK i have a 67 stang with a 200 and c4 tranny. I recently got my car up and running and the problem im having is that in order to keep it turned on i have to have the idle at a very high speed. and if i dont when i put the car it gear the car shuts down on me. Also i recently put in a rebuilt carb and noticed that it makes a wierd slushing/sucking noise at all times and im not sure if this has to do with the problem. Before the new carb the car was running fine and im not sure what happened. The old carb just gave up on me one day so this rebuilt carb was a must and now i feel that it made things even worse since i cant even drive my car.

any ideas how to fix it would be appreciated.
 
I'd give 10:1 odds you've got a bad vaccum leak. That sucking sound is just that: air be sucked in from somewhere OTHER than the throat of the carb. Probably look for unplugged vac lines around the base of the carb. Some of them are VERY hard to see..tucked way in. WHich carb do you have?

Start there. If all of your vac ports are plugged or tied to something, you'll want to check around the base of the carb where it meets the intake or spacer. You can use starter fluid in small bursts sprayed down there with the car running. If there is a vac lean, the fluid will be sucked in and the idle will change noticeable. You can also use a propane torch UNLIT..just open the gas and prod it around the base of the carb. Listen for idle changes.
 
ok can anyone tell me a step by step on how i would check this vacuum leak. i really am not sure where to even start. i had a mechanic look at it not to long ago and he said its the carb thats the prob.
 
first, which carb do you have? That will help us ID where you may have an open port.

If that's not the case, you can use the method I mentioned above (starter fluid or propane torch). Simply take the flamable item of choice and spray it lightly around the base of the carb (for starters) with the engine running. If the idle changes, that means it's sucking the stuff in...that's bad. You can identify pretty closely where the leak is that way. Resolution ideas will come after you ID where it is.
 
do you have an old carb to switch it out and see if it is the carb?

I love proving mechanics wrong.......
 
ok well i havent had a chance to swap carbs but something i wanted to add was that since i put that rebuilt carb in mt exhaust has had alot more smoke coming out of it. not sure if this could be in part of the rebuilt carb or if its the motor.
 
if you didnt do anything ot motor....i would suspecty its the carb running too rich
 
ok im not sure if this is a big deal but earlier when i was looking at my motor before i had to go to work i noticed that the carb has 2 gaskets under it. i think my mechanic installed 2 of them to stop it from leaking gas. Could this be the reason that i might have a vacuum leak?
 
there shouldnt be more than one gasket..if he added an extra one then i think thats pretty dumb...u can get different thicknesses of gaskets too...u can get the cardboard thin ones or the 1/4" thick ones...i like the thick ones best. but there should be 2 gaskets...one between the intake and the spacer and one between the spacer and the gasket. i had a vacuum leak (using the thin gaskets) i just took some of that black gasket sealer stuff and did that cause i was getting really sick of it leaking...that fixed it just fine. But most of the time if your idlespeed goes up and down its a vaccum leak.
 
Your carb may be running too rich. As you mentioned a higher idle speed would be required to keep it running and might also give you a loud sucking sound since your plates are openned further. You may need to check your float setting. You might also have too large of an idle jet. Check to see that the fuel mixtrue screw works and is not damaged. It could be that the screw is damaged, and will not meter the fuel properly. Depending on the carb modes, some have metering rods or power valves that adjust fuel delivery depending on engine vacuum. Springs and metering rods can be replaced to tune the carb to your car's configuration.
 
Does it speed up or slow down if you partially block the throat of the carb with your hand.
 
if you have the wrong carb base plate gasket ( like the autolite gasket with 4 holes plus the venturi hole, under a holley you will ge a vacuum leak )
I would start there, 2 gaskets is one to many and most likely your problem
 
ok well hopefully this weekend ill have time to get under the hood. Whenever i put my hand over the throat of the carb the car begins to slow down and shut off. Im going to try to take off one of the gaskets hoping that maybe it is just a gasket problem.
 
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