whats wrong with my carb?

[woodyy24]

holley 600 double puumper.

first start the car up and it will idle fine at about 700-800 rpm and after about 30 seconds it will sputter and die.

if driven it will do the same thing, but if i get on it really hard it will start to run fine again, then 30-60 seconds later same thing will happen.

im positive its the carb becasue i let my buddy use it on his 305 nova and the same sh1t happens.

i figure its dumping too much gas, but what could cause this? and what should i look for if i take it apart?

also my fuel pressure is 7-8 psi and so was the novas.

 

[latamud]

Check your float level. You might be running the bowls dry if the floats are too low, or floading if too high.

 

[srothfuss]

Sounds like it's running rich.

What do the plugs look like after your car starts acting up?

 

[woodyy24]

i had just put brand new ones in there, when i checked em they still looked brand new.

 

[Bad92GT]

how about trash in the bowls?? jets clogged? try a smaller jet in it first and see what happens

 

[mr.b]

--adjust the idle mixture screws for highest vacuum (after the car is warmed up)
--did u mess with the jets? put the stock jet sizes back in (if not sure, go to holley's website and match up your car number and it will tell the stock sizes)
--how much vacuum does it pull at idle? make sure power valve is at least 2" less than the lowest vacuum the car pulls
-make sure the power valve isn't popped.

basically sounds the car has too much fuel because it needs more when cold and then when it warms up it has to much

 

[FORCED2DV8]

Check your plugs and see if its running to rich, If the other things check out you might have an orfice thats partially clogged or dirt in it. make sure it has a good seal to the manifold as well all vaccum line or ports are hooked up or plugged.

 

[woodyy24]

thanks guys. im gonna open it up today and see what i can find.
i havnt messed with the jets since i first put it on my car (cant remerber the jet sizes either) and have never had a problem with them, i tried setting the idle with the adjustment screws but it wouldnt stay still and kept dieing. it has a good seal on the intake and good gaskets.
on the cold needs more fuel thing. its weird because if i floored it when it was warmed up, the sputtering would stop for a little while (about 30 seconds) and start again. it wouldnt do it on downshifting either until it got near idle rpm. no idea what the vacuumm is at.
whats a blown powervalve look like?

 

[mr.b]

put some new metering block and bowl gaskets on it. could have a gasket leak in the metering block area. I had this happen one time, could never get it to idle good and it would stall out a lot. check the power valve by putting it up to your mouth and sucking on it and seeing if it moves in and out (don't do this to much you might excite yourself!)

 

[Dark Knight]

Jets wont do anything at idle. Sounds like the needle valve has dirt in it, primary or secondary, holding the valve open so it doesnt shut the fuel off. With it running, look into the carb and see if fuel is dripping from the boosters.
Might also have to much fuel pressure, pushing the needle valves open. Check the fuel filter too..