Well I've been fighting getting my rebuilt L69 to idle right.. Its got WP heads, comp cam 262, Edelbrock intake, headers and full exhaust... After I put it back together I couldn't get it to idle at all.. it would run for about 10 sec then die... I replaced all the vaccum lines and now it is MUCH better... but still not there yet.. It does fine until it warms up, I can drive it around, but sometimes when I pull up to a light it just dies, or idles super rough, unless I rev it up a little.. Could this still be a vaccum problem?

I read a few threads about using starting fluid to check for leaks but I must be doing something wrong.. I can spray it right in the carb and all it does is bog a little, not rev... How could a little leak in a line suck enough staring fluid to make the engine rev? I did disconnect a vaccum line from the carb while it was running and it almost seemed to smooth out a little... might have just been my imagination..

 

Best bet is to go buy a vacuum guage from a auto parts store. You should be able to get one for around $10. It will confirm if you have a vacuum leak, and it has other uses as well, such as setting the carb to get the best vacuum at idle.

You can use starting fluid, as well as soapy water, wd-40, and propane to try and find a vacuum leak. I've always used soapy water or wd-40. Spray the area you want to check, lets use the carb/manifold gasket as the example. Spray a small area around the base of the carb and see if the idle changes. If using the soapy water, see if there are any bubbles that appear. You should be able to track it down this way. Also, if you haven't done so already, go back and make sure all your intake manifold and carb bolts are tight. The intake bolts have a habit of coming loose after a couple of heat cycles. A friend of mine had a vacuum problem and when he checked his manifold bolts, all of them were so loose you could take them out with your fingers

Hope this helps and good luck with the motor