I did a search, and found nothing. The 750 DP on the Camaro is running real rich. THe jetting is 69/74, but it runs rich at idle. I have all 4 mixture screws bottomed out, and it still runs rich, he||, it still runs with them all the way in. I have the FP at 6psi, and the floats are below the sight hole. At idle, the power valve should not work even if it is blown, correct? Vacuum is a good 10 in. at idle, so I didn't think the cam was causing this. Timing has been moved from 30-34, with no change. I have noticed, if I run some 110 in it, in doesn't run as rich but I also advance the timing a bit to smooth the idle with that fuel. Any suggestions what to do? I have had the carb apart 3 times, and cleaned it everytime.

 

The throttle blades are probably open too far at idle. Check the secondaries to insure they aren't at fault.

The primaries should be open enough to just uncover the transition slots (about the same as the width of the slots). The only way to check for sure is to have the carb off, set the idle speed screw to get that uncovery. Try 1-1/2 turns out as a starting point on the idle mixture screws. Put it back on that way and adjust the idle with the mixture screws only - you may have to keep it running by holding the throttle open by hand a little, but try to adjust the mixture screws so it will idle when you let off the throttle.

Oh, make sure the ignition is doing its thing properly - timing being one critical parameter.

 

Probably a blown PV. IF fuel isn't overflowing out of the bowl, and the idle screws are closed, and it still runs, gas is getting in somewhere else. 90% of the time it's the PV.

 

Jester, I thought the same thing, but I read that the PV is part of the main circuit, and at idle, that circuit isn't open.

 

When it's intact sure. When it's ruptured it exposes manifold vacuum directly to the fuel bowl. makes for a hell of a leak.

 

Well, it looks like Joshua is going to be pulling that carb apart then. Thanks guys.

 

I'm currently trying to equalize the front & rear openings. Basically I opened the secondaries just a little, so I could close the primaries a little.
But like 'Five7Kid' mentioned my primaries where uncovered too much.
I was going to test it as soon as it warms up around here!!! For now it's on display like art work

BTW: Mine is a four corner idle, so I have to balance it just right.

Ron

 

Ron, I have the four corner deal too. I am going to try to close the butterflies like they suggested. I don't think the power valve is blown, the car has ran for like 20 minutes since I put in a new trying to nail this problem down.

 

Heres a photo to help in adjusting the secondaries.
Beyond adjusting the secondaries, there the old drill a couple of very small holes in the primary blades (AS A LAST RESORT)...




Ron

 

Okay, I'm following what you guys are saying, but when do I know its time to adjust the secondary butterflies? Do I do this if I have to uncover to much of the transfer slots on the primaries to get it to idle? Then try the secondaries? And then if that doesn't work, drill the holes? How far is to far for the secondary blades? Do they have transfer slots to use as a reference also?

Thanks for all the help.

 

One important factor, is that the car is completly warmed up, when adjusting the idle speed, and idle mixture. Take it for a 15 minute spin before starting. Also make sure your plugs are not already fouled...The spark becomes real lazy, and the car becomes a turd to start if there fouled.

If you find that you can not get the idle mixture to respond, try 1/4-1/2 turn on the secondaries. See if that lets you close the primaries enough to allow idle mixture adjustments. I would open it in very small steps.

..and yes the secondaries with four corner idle have transfer slots, but are not affected by the idle speed screw. Thats why I say it's a balancing act


Ron