Need Rochester carb expert

[Tim anderson]

Been a long time since I've had to work on one.

What to look at if:

Throttle plates are in normal position. (still covering idle slots)
Float is set correctly. (no cup runnith over anyway)
And gas is pouring out from the venturi port for main metering. (while running and won't idle below 1200 RPM.)

Could this be caused by float not seating, yet not runnig out of the vent?

Thanks

[Clem Z.]

Re: Need Rochester carb expert

check the float level again and check the float for heavyness also make sure the floats are not hitting the sides of the floatbowls. check to make sure the bowl vent is not blocked

[Shannon Burgess]

Re: Need Rochester carb expert

I had a very similar problem on my '69. It was due to a burned-through gasket between the intake and the base of the carb. The area by the heat crossover passage had burned through from the exhaust gasses, and was causing a vacuum leak. This was keeping the power piston from pulling the primary needles down into the primary jets abnd the carb was loading up very rich.

Just a guess.

Shannon

[Tim anderson]

Re: Need Rochester carb expert

I went back and rechecked the float. And lowered it a 16th just for fun.

No change. I pinched off the fuel line at the pump intake. Ran it out of gas. And until it died it pulled from the main discharge.

Am I correct that the idle gas discharges at the slot by the throttle plate.
And the main circuit should not discharge at idle.

Could this be a totally disfunctional idle circuit?
Thanks

[Joe L.]

Re: Need Rochester carb expert

Tim-----

I'd recommend doing like Clem mentioned and checking the float for "heaviness". Rochester Q-Jet floats are made from a nitrophyl plastic material which is coated with a gasoline "impervious" coating. In time, the coating breaks down and the nitrophyl material begins to absorb gasoline. That's the end of the float.

You can do a crude check by placing the float's angled bottom surface on a flat surface. If the float will not stay balanced on the bottom surface and "tips over" to the metal arm side, then the float is probably ok. However, if it will remain balanced on the base and not "tip over", it's likely junk.

New floats are available from GM/Delco or aftermarket sources. Actually, although they don't come with most rebuild kits (even the so-called "major" rebuild kits), I ALWAYS recommend replacing Q-Jet floats when rebuilding the carb. They might last 2 rebuilds or they might NOT. Why take a chance?

[Clem Z.]

Re: Need Rochester carb expert

if you are talking about a Qjet nitrophyl float it should weight 10 grams.never use a brass float in a Qjet and if the carb is not a Qjet the brass float can be just shaken to see if fuel has leaked inside.

[Tim anderson]

Re: Need Rochester carb expert

I wish it was the float but.........My life with project Corvette could not be that simple.

[Craig D.]

Re: Need Rochester carb expert

Tim,

Exactly the same thing happened to me with my 73 last month.It was the float level.I would try lowering it one more fraction.Lowering too much can cause a stumble when you accelerate.My problem stopped but I could not set the float at exactly factory spec like it tells me to.I did not want to buy a new carb so I took a shot and at this point it is ok. We'll see if things change.good luck. Craig