Fabricating a Fiberglass/epoxy intake manifold. John De Armond, johngd@bellsouth.net Note: These photos are stored in a fairly high resolution format so that they may be downloaded and printed or viewed magnified. The pictures illustrate the steps involved in fabricating a fiberglass manifold for a Datsun 260Z engine. This engine originally used 2 SU-type carburetors, each one feeding one carburetor. The manifold is designed to adopt electronic fuel injection to this engine in as simple a manner as possible. One Mazda RX-7 high volume injector feeds each bank of three cylinders. The construction materials are fiberglass cloth and mat and Hysol high performance aerospace epoxy available from Alexander Aeroplane Company. The cost is moderate but the performance, particularly at high temperature is remarkable. One caution: This type of epoxy is known to cause first sensitization and then allergic reactions in susceptible individuals. Reactions can be severe enough to cause life-threatening anaphylactic shock. The process is insidious. Exposure to the uncured resin the first time causes sensitization (an immune system response) to the chemical. Subsequent exposures cause severe allergic reactions. Hysol has reformulated the epoxy to reduce the effect but it is still possible. The ONLY protection is to wear the proper gloves and respirator to prevent skin or lung contact with the epoxy or its vapors. Making this type of manifold involves forming bucks (internal mandrels) that the fiberglass is laid up on. Other types might involve forming bucks and molds used to shape both the inside and the outside. Flanges are made by laying up multiple layers of fiberglass and resin and then compressing it to squeeze out excess resin. The fiberglass supplies all the strength so it is desirable to have as little resin as practical. Photo 1 shows the raw materials used for making bucks. Wax bucks can be used since the epoxy is room temperature cured. It can be melted out after cure using a pot of boiling water. Runners are formed by pouring molten wax into molds made of PVC pipe. The wax must continue to be added as the wax cools and shrinks or else there will be air bubbles in the buck. Placing the mold in the freezer will shrink the wax enough that the buck will fall out of the pipe. The tapered part of the manifold in this case was cast using a milkshake cup. To mold the buck to shape, heat it in a bath of warm water until soft. Est. about 115 deg water. The wax should be flexible but not gooey. After it is molded to shape, spray the buck with cold water to set the wax. Allow to cool thoroughly, preferably in the refrigerator before handling. The transition between the plenum and runners is molded by heating wax just above its melting point, pouring onto the pieces fixed in place and then wiped with the gloved hand. A heat gun will flow the wax to make a smooth surface. The fiberglass picks up the exact surface finish of the bucks so for the smoothest finish, pay attention to the wax surface. Photo 2 shows this detail. Photo 3 shows the finished buck and photo 4 shows the buck suspended by strings and coated with the first layer of epoxy. This is a thin layer, a "gelcoat" to form the inner surface. Only after this layer is cured is any fiberglass laid on. Photo 5 shows the first layer of fiberglass in place. Photo 6 shows the first layer of vacuum bagging in place. Alexander Aeroplane's catalog shows the details of vacuum bagging. The bagging compresses the fiberglass and squeezes out the excess resin. It also holds the parts in place during cure. In these photos an air conditioner service compressor was used for the vacuum. This is hard on the compressor and is not recommended. The compressed-air-operated venturi pumps are much better because they are not affected by contamination like mechanical pumps are. Photo 8 shows the assembly after the first bagging is complete. The epoxy has leached the ink from the plastic bag. The manifold is ready to go Krogering :-) Photos 9 and 10 show the flange blank being formed. This is done by laying up multiple layers of fiberglass, each layer with the grain oriented 45 degrees to the previous and then pressed to squeeze out excess resin. This makes a very strong but light blank. Photo 16 shows my friend Jerry using a carburetor spacer to lay out a flange that mates to the existing manifold. Photo 15 shows the throttle body flange being fitted to the manifold. Photos 8 and 9 show the flanges being attached to the manifold using vacuum bagging to compress the fiberglass. Photos 17 through 20 show the fuel injector bungs being attached to the manifold. For the Mazda injectors being used on this project, it happened that the nut used to attach a regulator to an argon cylinder fit the injector perfectly. Therefore two nuts were molded into the assembly. The threaded body aided in bonding the bung to the manifold. The bung was ground flush using a die grinder after the epoxy had cured. Photo 21 shows the throttle body being attached to the manifold. A balloon is being used to exert pressure on the fiberglass inside the manifold. This does the same thing as vacuum bagging does on the outside. The rest of the photos on this page show the manifold as it is being finished and with the throttle body attached. This was one of my first manifolds. Later ones used metal inserts for threaded portions and where clamps attached. Silicone spray or better, PVA (alexander aeroplane) is used as mold release to get the epoxy not to stick to the mold. This manifold has been in service since 1992. This article and pictures are copyright 1999, John De Armond, All rights reserved. This material may not be reproduced in any manner without my prior written consent. John De Armond johngd@bellsouth.net -- Alexander Aeroplane Co PO Box 909 Griffin, GA 30224-0909 800-831-2949 Another source: Aircraft Spruce & Specialty Co. 201 W. Truslow Av. Fullerton,CA 92632 800-824-1930