High idle speed?

[Shaggy]

I need help troubleshooting a high idle speed problem. I bought a vacuum secondary 600 cfm 4160 on Ebay and rebuilt it using a Holley kit. With the idle speed screw backed all the way out it still idles at 1100 rpm, engine specs below. When the idle mixture screws are adjusted for max vacuum it pulls ~17in +/-1, and only varies with engine rpm. I know the previous owner tried to do some “modifications”, like putting a sheet metal screw in the vacuum secondary linkage, but I don’t know the extents to which he went to “modify” it. If this thing ends up in the dumpster I can deal with it, as long as I know why it ended up there. I’ve got about $80 invested in this thing and I’d like to use it if possible. Anyone have suggestions on things to try/check?

235 cid V6
Holley Single Plane Intake
Cam duration @ .050” = 204 Int & 214 Exh
Valve Lift = 434 Int & 457 Exh
Heads are ported 8445’s
Compression is 9.0:1

[DaWildcat]

Any evidence that the throttle shaft(s) are binding, or that the blades are no longer centered in the bores? This can happen if someone tries to take the blades off the shafts for a rebuild.

Devon

[Shaggy]

There's no binding and the throttle blades are centered. I looked at the blades when I was doing the rebuild and it didn't look like the guy had tried to remove them. I was looking for evidence of drilling/cutting when I had it apart, nothing was glaring. :Do No:

[Shaggy]

Problem solved... The charcoal canister was the source of a major vacuum leak. :Dou: I now have a nice steady 680 RPM idle with 15" of vacuum.