Copied,condensed 3 posts,from elsewhere. 427 Street car,trying to make it civil as possible.
The big Holley HP 1000,was giving me fits. Set the mixture screws for a clean idle (about a 1/2 turn out x4) and it would idle at 1100 + with the idle screw backed completely out. This was with the black bushing in the MSD distributor and the stiffest springs. About 17 initial 33-34 total,all in around 3600 (slow) Trying to bring the timing in quicker with lighter springs,made the high idle problem even worse. I have about 10'' vacuum at 1k.
Long story short,swapping the stock drilled throttle plates for solid ones and 79 idle air bleeds,has the motor returning to idle nicely. Currently using 2 blue springs,all in around 2500. Not perfect yet,but a lot more fun to drive.
Jetting is 84-84. Dropped 82's in the primary. Hard to explain the improvement in driveability. Pulling away (smoothly) from a stop,has become much less of a chore. Able to cruise at 1500 in 5th,if need be.
For comparison,on day 1 the car was unhappy at anything less then 2300.
Will try bringing the timing in a little quicker next (blue/light silver) all in around 2k.(no vacuum advance) Maybe drop the primary some more,or larger air bleeds ?
I am thinking with more moderate temps,40+ 81 primary and more pump shot. (.031 now) would be worth trying ?
A question about holley jets. #84=.099 #85=.0985 Could the 85 flow more fuel ?
427 T56 3.90 2 kits