[87monte385]

my car starts right up, and idlels fine, drop it in gear and runs fine, but after driving just a little bit when i stop and try to let it idle, it doesnt want to and i have to keep my foot into it and right at about half throttle it starts to break up.. any ideas?? timing is at about 35 degrees and im running race gas

[cobalt327]

One thing to check is to see if the choke is partially closed.

[bigdog7373]

Set the idle speed when the engine is at operating temperature. When the choke is on it idles faster to warm up and when it warms up it slows down again. I'd have to say that when the choke is off it's just idling too slow.

[87monte385]

i havent used the choke on it yet, its always been open.. i took off the front bowl because when i shut the car off gas was still dripping in, turns out there was teflon tape plugging the needle and seat, i cleaned it but still the same thing it dies when ive been driving and when i come to idle in gear, also it breaks up when im at about half throttle and i get on it, the carb. is brand new...

[bubbahotep]

Hows everything fuel related?:

Fuel pressure?

Floats levels?

Idle mixture screw adjustments?

Brand new carb might just need a quick tuning. Is the cam radical enough to cause low vacuum at idle? Not something simple like a vac line getting warm and loosening up / leak?

[Aerotech]

Check that needle and seat again. Sounds like you might be running the bowl dry and it's not filling fast enough.

[87monte385]

the cam is a lunati voodoo with about .560 lift and i didnt know if when i hit the brakes to slow down to an idle, if that has anything to do with it? ill try to adjust the float levels again, its a pain with no sight glasses..

[cobalt327]

Originally Posted by 87monte385

the cam is a lunati voodoo with about .560 lift and i didnt know if when i hit the brakes to slow down to an idle, if that has anything to do with it? ill try to adjust the float levels again, its a pain with no sight glasses..

Which "650" is this- need the number off the carb.

[87monte385]

its a 4150 model and the number is, 0-4777C

[Aerotech]

Sounds like float adjustment or needle and seat problem. I like to adjust side-hung floats dry. Hold the bowl upside down and adjust the float parallel. This will usually equal a perfect wet adjustment. If your needle and seat already had tape debris, just get new ones. This may not be the ultimate solution, but it is the first thing you should do.

[87monte385]

so, taking the front bowl off, hold it upside down, and turn the set screw in so that the float is horizontal in the bowl?

[cobalt327]

Until the bottom of the float is parallel to the bottom of the bowl, but this can also be done w/a drill bit if you have either side hung or Duracon floats.

More here.

The dry setting for a brass float is to center it exactly in the bowl, w/the bowl inverted. From HERE:

[87monte385]

ill try that. today i started my car and it was running fine then i shut it off and looked in the carb and didnt see any fuel and i was holding fuel pressure still, so i think i took care of the needle sticking open. but i drove it up the driveway and was backing it down, i gave it a little gas and hit the brakes(not much) and the car died. i started it back up and put it in reverse and let my foot off the brake and the rpms went up then came back down.. im at a loss at this point..

[bubbahotep]

Possible vacuum leak? Seems to happen when you brake. Got all your vac ports plugged or tight on the hoses?

Does it ever happen if you mash the gas in park? I would think that a dry bowl would occur in park too

[87monte385]

i beleive i have all my vaccum ports plugged and tight.. i went over all of them..