I was checking my idle vacuum last week and noticed a leak around the idle mixture screws (specially the passenger side one). Is there a way to fix this? Are there gaskets that can be installed under the screws/springs, I've never had these out. The tip someone gave me last week worked great while trying to locate a vaccum leak (thanks! :TU: ) . I used a rubber hose; one end in my ear the other end sniffing around for that sucking sound.
It is probly the baseplate of you carb leaking. Just remove the carb, put in a new gasket, and use some rtv sealant. It will run better too.
Do NOT use RTV. RTV is not stable around gasoline, it will turn to ugly jelly. There are gasoline safe gasket sealers, but you should NOT need a sealer on a carb base gasket. Clean, dry, straight (not warped) parts, torqued to spec, and you're done.
Seal All. Gas oil & nuclear proof. Some bad a-- clear stuff. You can find it most any where. Its a red n yellow package. Look kind of like PB blast the way it has that old fashion writing all over it with facts n stuff. Works great for sealing or gluing most anything.
The base plate was already replaced, initially I thought that was the problem. Changing gears: The big vacuum leak I found was under the master cylinder, close to the booster. Anyone ever heard of a leak there before? Seems it's leaking through a vent that goes to the booster? Is this common? Not sure but I think this 2nd issue is master cylinder related vs booster related? Ideas? I temporarily plugged the leak to increase vacuum so the brakes worked better. Time for a new master cylinder I guess...
gasket between the throttle plate and carb body? I seriously doubt the screws would leak so bad that you could hear the air escaping. Did you spray carb cleaner around that area to see if you could get the idle to spike? If you're dead set on the fact that the screws are leaking, then take a very small amount of bearing grease and put a coat on the threads of the screws. Do this very sparingly....it should be enough to plug any air that is escaping/getting sucked by the threads.
Craig, That is too far out. The carb will react better with a leaner idle mixture. As you turn the screws out, the ideal idle mixture is somewhere between maximum rich, and lean misfire. No wonder you are leaking vacuum. The needles are out so far, you can probably wiggle them. You'll probably fuel foul the plugs if you idle it too long. Try this. Pull off a full vacuum line. If the idle immediately increases, it's too rich. If you choke it out, and the idle goes higher, it's too lean. When you cause a deliberate vacuum leak, the idle should drop off some, if it's adjusted correctly.
How far out did you have to adjust your fast idle screw? On my new motor with 413 cam I have to adjust way out. Then you are into the next step in the carb. Makes you think you have a vacuumn leak. I think that I may have to drill a hole in the primary throttle plate to tune the idle in properly. I do have it at the OK point right now but not what it should be. You may be experiencing a similar problem. Also the curb idle hole (the part your needle fits into) may be too small. Again these are problems you can get with a larger cam.
