Holley 4000 Technical

Spring Loaded Needle & Seat

The type of needle & seat which works with the spring-loaded retention system is no longer available. However, the needles used in them are identical to those used with the threaded seat. Some kits contain instructions to simply use the new viton-tipped needle in the original seat and discard the new seat.What Does The Spark Control Valve Do?The spark control valve in the passage from the throttle bore provides an efficient degree of spark advance during periods of acceleration by momentarily providing a partially retarded spark. This partially retarded spark minimizes detonation, or pinging and increases engine responsiveness while accelerating. In effect, the spark valve provides an intermediate spark advance curve between a fully retarded spark and the normal spark advance which would be excessive when the engine is suddenly accelerated. The spark control valve accomplishes this by controlling the manifold vacuum admitted to the distributor vacuum line.

Removing stuck discharge nozzles.

Refer to #30. Please note before doing this that you can distort or crack the bowl housing. Take your time and be very careful. Grind the tip of a screwdriver tip to fit into the keyhole-shaped recess in the top of the discharge nozzle. Try to move the nozzle back and forth, but take your time with this. Any movement at all is a sign that they will probably come out if you work them long enough. Sometimes adding some heat will help. Now using a sharp blade or awl tip driven into them above the "duckbill", as horizontally as you can, pry against the adjacent casting.

Holley 4000 Carburetor Kits

Here are the various kits that we have for the 4000. There are subtle differences in the kits, so be sure to use the carburetor number and match to the list contained in each carburetor kit.

It is probably a vacuum leak due to a bent "boot" at the front of the bowl. You see, one side of that boot has a cast-in breech tube for the idle circuit (which recesses into the idle passage), the other does not -- makes no sense whatsoever, but there it is. I'll bet that it is the side without the breech tube which is causing problems. Put 1 or 2 more gaskets under the boot to see if that will solve the problem without lifting the front of the bowl too high to seal to the choke air horn. Using a very thin coating of Permatex Anaerobic Gasket Maker around the gaskets' passage holes can't hurt, either.

Running in a rich state has two basic possibilities. The carburetor is in a flooding state, or there is a vacuum leak. For the vacuum leak you can spray carburetor cleaner around the mounting flange gasket, intake manifold and around any fitting, or line connected to a vacuum port. If the engine RPM smooths out, then you found your problem. Assuming there is no vacuum leak, then the most likely cause is the carburetor is flooding. In simple terms, flooding means that there is too much fuel getting into the manifold. Here are some things to check out. Eliminate each one carefully.

There may be a few more things I haven't thought about, but this should give you plenty of things to think about. Also, the history of the carburetor should give you some hints on where to start. If this situation started only after you rebuilt the carburetor, then obviously the problem is probably related to something you installed, or forgot to install.

The spark control valve in the passage from the throttle bore provides an efficient degree of spark advance during periods of acceleration by momentarily providing a partially retarded spark. This partially retarded spark minimizes detonation, or pinging and increases engine responsiveness while accelerating. In effect, the spark valve provides an intermediate spark advance curve between a fully retarded spark and the normal spark advance which would be excessive when the engine is suddenly accelerated. The spark control valve accomplishes this by controlling the manifold vacuum admitted to the distributor vacuum line.