Well, in the never ending saga which is my car, like many other peoples, I am now trying to tune the darn thing. I stopped my intake leaking, I put a new one on it and I can now get 10in of vaccum out of it at idle in park. When I put it in gear I have 6. Does that sound low?

The car smells rich all the time, cruzing, WOT. The plugs are burning good but they are not white, they have a light black color to them.

When I was trying to tune the idle mixture screws the other night, when I idled it up, i could hear air being sucked through the throttle blades. I could slow the idle down to about 600 and the noise would go away, but I wouldn't have but 8 inchs of vacuum or less. Also, when I turned the air screw all the way in, the car wouldn't die, I thought it was supposed to?

I changed jets in it from 74/81 to 76/78, and changed the pink cam to the green cam I think. I know I shouldn't have changed two things at once. The car does feel more peppy on the primary side, I don't have to push the gas down as much to get it to move, I thought it didn't pull as hard up top but I got on it today and it felt good, the butt dyno isn't always a good indicator.

I have a 4.5 power valve
76/78 jets
green cam in front, pink cam in back
squiters are 31/28

Initial timing is 14 degree, total I don't know because the MAC man hasn't brought back out adjustable timing light yet.

I know pretty much jack when it comes to tuning a carb, it's something I just haven't done yet. I know there are several people on the boards that are knowledgable about carb tuning. I guess I need to get a holley book and start reading.

When you rev the car up it smokes some, but then goes away. It looks black smoke.

thanks for any help.
Jason

 

You've got a lot of cam to be expecting good manifold vacuum. I would expect the engine to have a normal idle of about 1,000 rpm. What's in it now for a torque converter?
How far are the idle screws turned out from the bottom?
Does the carb also have a secondary power valve? May be some of your problem too.

 

What carb do u have? model #....

When you can turn the idle mixture screws all the way in and it still runs its because fuel is leaking into the motor somewhere else. (Leaky metering block gasket, float level too high, powervalve diaphram leaking or dirt holding the power valve from seating at idle.

 

I would be expecting that if the engine was a 350, but I figured a 406 would be able to handle more cam. My friend has the exact same setup in his pontiac 455, and only pulls 12 inchs of vacuum though.

the converter is a 9.5 ACT 2800 stall

Car idles about 1000 in park and about 900 in gear, it doesn't want to die, chug or anything like that, I can idle it down to about 700 actually and it still is ok.

I don't know about the idle screws, I used a vacuum gauge when I was doing it and wasn't paying attention, i think about 1-1/4 turns out.

I don't have a secondary power valve, however my friend with the 455 has a four corner idle on his 750DP, and the 2ndary PV is blocked off, he bought it that way, what does a 2ndary PV do?

does a 4.5 PV sound right for the vacuum I am pulling?

The carb model # is 2538

thanks for the input, i do appreciate it
Jason

 

When I spoke with the Holley tech, he recommended a power valve that's closest to half of the idle vacuum in drive.
Power valves are an additional enrichment circuit.
If you did have one and decided to block it off, you would have to jump the jetting up a bunch of numbers to compensate.
His 750 must be the HP series (race) since that's the model with 4 corner idle.