HOW TO INSTALL A LOW COST HOLLEY 2 BARREL CARBURETOR

The Holley 500 cfm $300 2 barrel seems to be it if a way can be found to lean it.



There are several options out there for that. See below.

Why is the 500 cubic feet per minute Holley needed when the rotary is only about 160 cubic inches? The answer is the p-port rotary will take in 20% more air than a piston engine due to its lack of intake valves and the tuned intake manifold. Here is a chart showing the air flow requirements for different displacements at different RPM's. One must multiply these number by 1.2 to get the airflow for a p-port Mazda rotary. That makes a 13B rotary equivalent to a 200 cubic inch piston engine. Note however the power is twice as high because the RPM is doubled.



The main problems are it must be mounted vertically and the height is rather high so getting it under the cowl is a challenge. This is one way I have come up with a configuration that still gives the right length tuned intake pipes for an RX8 P-port engine. HP should be well over 220 at 7500 RPM. These manifolds are made from 6061 2 inch OD .065 wall (16 gage) tubing bends with a 3 inch center line radius. Burns Stainless sells this stuff among others.











The spiral manifolds are made from 180 degree tubing bends.





This should be quick to build and straight forward to install. Could save as much as a year compared to electronic solutions.

It is kind of interesting that the RX8 p-port does not need a slide throttle or butterflies located in the rotor housings because it is a side exhaust with a peripheral intake configuration. It idles as well as any Mazda rotary engine built up to the RX8. The roles of the p-port are reversed. Side-exhaust p-port-intake rather than side-intake p-port-exhaust. As far as power generation is concerned it is far more important to use a p-port intake compared to a p-port exhaust. This is due to the modest pressure difference across the intake port.

So the answer is; the slide is not needed however the butterflies in the carb cause a bit of power loss due to their aerodynamic drag.

Organ pipe tuned engines with carbs on the ends of the pipes are notorious for what is called fuel vapor stand off. It is a cloud of fuel vapor that hovers over the carburetor when the engines is on the pipes so to speak. The plenums at the ends of the pipe mitigate this phenomena at the expense of some power. A ram air box will still be required to contain this fuel vapor.

Paul Lamar

Tom McNeilly tomcn@earthlink.net

Here is some information about the Holley mixture control kit. It is best suited for a two barrel 350 or 500 CFM Holley carburetor. However, the unit has been successfully used on large four barrel carburetors. The mixture control WILL NOT fit other makes and models of carburetors! The unit replaces the fixed main jets with a rotating valve that is remotely operated by a push pull cable. The unit will go from total idle cut-off to overly rich by rotating the shaft, while the engine is running. Installation is very simple with step by step instructions provided.

Due to the outrageous cost of materials and the inflationary state of our economy,the price of the kit has recently been raised to $150.00.

The mixture control body is CNC machined from 6061-T6 aluminum which is alodine treated, the shaft is stainless steel and the screws are plated steel.

The first picture is what comes in the kit. The mixture control plate is in the background with the accelerator pump extension arm., power valve block off plug, and installation bolts in the foreground. I also include a set of three gaskets which are not shown.



The second picture is a unit installed on a 4 barrel Holley carburetor. The installer is responsible for the push-pull cables and attachment hardware. As you can see, the unit is installed in-between the jet plate and the float bowl. This requires the use of longer float bowl bolts which are included in the kit. The arm swings thru 90 degrees of rotation from idle cut-off to full rich. The arm can be clocked anywhere on the shaft to make installation easier. The arm in the photo is in the full rich position and idle cut-off would be in the 4 oclock position. Two shafts are avialable to make full rich either in the clockwise rotation or counter-clockwise rotation. This sometimes simplifies the push-pull cable installation. I usually ship the counter-clockwise to full rich shaft, as this parallels the throttle rotation on the opposite side of the carburetor.



If you have any questions please e-mail.

Thanks

Tom McNeilly tomcn@earthlink.net>