67 330 original Q-jet professionally rebuilt, (several years ago but very low mileage). Linkages (maybe) on the carb will not let the engine go down to idle speed. I don't have a tach, and unfortunately my old engine analyzer stopped working, but I can hear it's high, maybe around 2k. Does come down when in gear. I removed the throttle linkage and the dash pot for test purposes, and the engine is at operating temp. Runs ok at speed, although a bit rich. Has good throttle response. Don't want to start fiddling with adjustments that may make it worse.
Any ideas?
A secondary question, and please, just facts. Will a 1406 Edelbrock work on the stock manifold, or is an adapter required.
Thanks.

 

Have you checked the choke operation?

 

The choke seems to work fine mechanically. Engine speed does not decrease with the choke flap opening. Even after a rev up.

 

Pretty sure you'll need the adapter since a stock 330 manifold is a spread bore while the Edelbrock 1406 (600cfm) is a square bore. Others will either confirm or correct me. Make sure linkages are adequate w/ sufficient clearances. It's been a long, long time since I owned my 1st car (1967 442) & I maintained the Quadrajet.

 

Yup, you'll need an adapter, and one that includes bolts since the intake doesn't have square pattern holes.
Is the throttle bracket sitting on the idle screw when it's warm and idling? If it's not touching then something is holding the throttle open. If it is touching, then maybe the idle screw got screwed in, or there's a significant air leak somewhere.


There's a bunch of things that could cause this:
choke not fully releasing so the high idle cam is staying engaged. With the engine warmed up, see if the choke blades are vertical. If not, push them vertical then give the throttle a tap. If it idles down then the choke needs adjusting.
linkage problem in the choke mechanism preventing high idle cam from rotating out of the way. Could be grime/muck, could be something bent. With the engine warmed up and idling get a good look down behind the choke body to see if the high idle cam is engaged. You can also try just turning the high idle screw a bit to see if it affects idle.
Could even be the throttle cable/pedal. Disconnect the cable from the carb to see if that lets the bracket move more.

 

E-brocks have both bolt patterns.

 

"Seems to be" does not mean that it is. The original Qjet is the best carb for your car. Fix it correctly, including the choke. I don't know who the "professional" was that rebuilt it, but few rebuilders actually have a clue about Qjets, and with the divorced choke on the 1967 cars you still have to dial it in once installed on the engine. The rebuilder can't do that remotely. As for the 1406, it's perfectly calibrated... for a 350 Chevy. Do you have the patience and stills to adjust the jetting for your particular application? Yeah, you can bolt it on and it will likely run. It won't be anywhere near correctly set up for your car.

 

1) Try disconnecting the throttle linkage after the engine is warmed up and see if it's effecting the idle rpm.
2) See if the linkage is touching the Idle Speed Screw on the drivers side of the carb after the choke is fully open. If there is clearance between the Idle Speed Screw and the linkage the choke is not disengaging completely. The screw should be touching the linkage with the choke open and engine warmed up.

 

My first thought reading this is whether the fast idle screw is adjusted properly? I know the choke is said to seemingly be functioning properly but is the fast idle adjustment in too far? Just thoughts that came to me…

…

 

I agree to check for a gap between idle speed screw and throttle. If there is a gap the choke is likely preventing it from closing. Additionally, I had a q-jet so called, professionally serviced myself and was having the same issue with idle but it turned out to be a burr left over from the casting of the back side of the new choke cam follower lever. I was able to get a Dremel in to clean it up without removing the choke and it now clears the "standoff." This solved my problem. If there is a gap as described, close observation of mechanical operation should identify the issue. Good luck!

 

When you set the choke, start it up, and then after letting it run for a couple minutes tap the accelerator, is there a noticeable drop in your RPMs?