Just bought and rebuilt by me for a gas mileage experiment on the 327. Idles as smooth as a rock, pulls an unwavering 17" of vacuum, but there is a huge flat spot right in the middle of the primaries' travel that is spiking the A/F ratio up above 20:1, causing a big stumble. Once you open the secondaries(mechanical) it takes off pretty good but that primary side is killing me.
There are 2 primary jets and 2 larger secondary jets and one large jet that I am not sure what it does.
I have almost $60 into this carburetor so I really want to get it sorted.
Problem #1, huge flat spot midway through primary travel.
Question #1, are jets for this the same as other holleys? I have nothing to compare to.
Question #2, is that large, centrally located jet a power valve of some sort?
Three things I've thought to try but have not tried yet:
1) disconnect PCV as this could cause a large enough vac leak to have it go lean in the primaries.
2) Adjust pump shot. Not sure if this will help as the take off is fine until I hit the mid-travel of the primaries. Should the acc pump even be needed at mid-travel?
3) Swap secondary jets into primary side to see if just being richer kills the flat spot?
I know the Holley economaster is kind of 'fringe', especially for this forum, and I've read about all I can find on the internet about them(which isn't much) but if anybody with experience with this carb can make suggestions I am willing to try. Thanks.