After putting the T-quad back on the 400 in my 73 NY I'm getting a surging/erratic idle.

The car ran great with a 670 Holley but I wanted to give the t-quad another chance after it started spilling gas out of the vents 2 years ago. I put a kit in it and adjusted everything as per the instructions and tips I read from Demonsizzler.

There is no bog and it goes down the road fine, but the idle is all over the place revving up and down on it's own. It might be fine for a minute or so then it will start slowing down and almost die, then it kinda fixes itself and speeds up a little and repeats the cycle. If I crack the throttle to say 1500rpm it's ok, but it doesn't like anything under that.

The idle mixture screws are about 2 turns out, but messing with them didn't seem to make much difference. Because of the surging idle vacuum is going all over the place from 12 to 15 or so. It's a steady 20" at 1500. The exhaust sounds choppier than normal as well.

It's a low comp 400 with a lunati 60302, timing is 18 initial, and 36 total.

I'm not ruling out that it's something else though.

Pulling the metering rod tree up all the way or pushing it down doesn't seem to do anything. If I put my hand over the choke or close it by hand the engine revs up and runs smoothly for a few seconds and then dies.

If I keep opening and closeing the choke by hand it revs up and runs smoothly.

Maybe it's as simple as vacuum leak I suppose.

when my eddie 1406 started dying at idle I shot a 3 second blast of starting fluid into each idle mixture screw port with the thin red straw and that flushed the dirt out & fixed it. Your symptoms sound a bit different from mine though

any ideas? I can't find any obvious vacuum leak.

Did you try putting a dab of grease over the throttle shaft ends? Sometimes they wear and create leaks

Also when you installed it did you check to see that the base plate was not warped? They can get bent if not tightened down to the manifold right. What kind of base gasket are you using? I seem to recall a procedure for finding vacuum leaks that involved spraying a little bit of starter fluid in the suspected area of the leak and when the idle improves you've found your leak...

Does anyone have a diagram, or know how the bowl vent arm should be adjusted?

It looks like the bowl vent is open at idle and is pushing the float down, not allowing it close the needle and seat fully. Though if that was the case I figure I should be getting gas coming out the vent tubes.

The FSM and rebuild kit instructions are not clear on this.

Forget it....The Holley is going back on.

I took the whole thing apart and double checked everything. There is slight play in the throttle shaft yes, so I took it out and greased it. I pre adjusted the idle so just a "square" of the idle slot is showing.

Put it back and it still idles like garbage. With the grease the whistle is gone, but it idles way too low with just the small slot showing.

It's a 73 440 TQ. .100 jets I think and 1966 rods.

Cam is 220/226 st 0.050 .475/.494 lift
8.0 CR

Well after bending that vent arm so it wasn't open at idle, and opening the mixture screws a little more, I have it pretty good now. Idle vacuum is a steady 18 and it isn't surging anymore.

I'll take it for a test run and see how she runs.

When the shaft gets sloppy enough it will hang open and you will need to lift the pedal with your toe. Just open a little. Common problem with Qjets too. Like the Qjet on my van.

18" sounds much better!

Base line adjustment with the metering rod tree is push it down and back off the screw till it stops dropping. Then go 1 1/2 turns up. Just note where it is before you change anything.

And the floats are measured off the gasket, not the metal off the carb top.

.100's might be too big. Don't quote me on that!

I need to get the stuff to re-bush throttle shafts. Lots of Carters in my shop that need some love!