[Jack21]

Mike,

You're running way too rich. And if your engine isn't pulling enough vacuum to keep 35 PV's closed, I'm surprised the e4ngine runs at all.

If your PV has 2 gaskets on it, remove 1. The PV could be pushing against the main body, and lot allowing the metering block to seal.

In fact, at this point, replace the PV with a PV plug (a Holley part) just to isolate problems. No getting on it!

While, we're at it, we're going to install another diagnostic. The main body has a small hole at the bottom of the primary power valve vacuum chamber. Thread this hole, and install a setscrew in it to plug it. Don't thread the corresponding hole in the baseplate so the setscrew won't back itself out. This will cut off the manifold vacuum from the power valve, AND the accelerator pump transfer passage just above this vacuum chamber, to the squirter check valve, and squirter.

An undocumented problem I've found on more than one Holley (some old and worn, some right out of the box). The primary power valve vacuum chamber draws fuel from an improperly sealed accelerator pump transfer slot where the metering block joins the main body. This gives a characteristly rich running engine, and stumble with any throttle application from off-idle, to cruise.

Extra fuel short circuits the accelerator pump squirter, and enters the engine through the power valve vacuum chamber passage in the main body, and throttle plate.

If blocking off the power valve vacuum hole seems to cure engine richness, and throttle stumble (because the squirter is now delivering good fuel shots), this may be the culprit.

Holley 4165's & 4175's have a small brass tube with rubber "O" rings on either end, that are fitted between the metering block, and main body.

The main body may be warped requiring it to be filed, or milled flat. A small casting irregularity in the metering block, or main body may require better sealing. Drill out the main body a short way into the transfer slot, with corresponding hole or chamfer in the metering block. A piece of brass tubing is then tapped into the hole in the main body side. A tight fitting "O" ring is then installed over the tube. Remove the piece of metering block gasket where the O ring goes. As the metering block is assembled on the main body, the O ring compresses, sealing the accelerator pump transfer channel, and power valve vacuum channel.

Remove the vacuum channel set screw, and replace the power valve. Power valve value = 1/2 idle vacuum + .5.

Pick up a Holley setup and tuning manual or two.