Building an Intake System
Or, How I Built My Intake SystemStory and art by Patrick Panzera, EAA 555743, firstname.lastname@example.org
It doesn’t take a rocket scientist to realize that if care isn’t used when bending ridged tubing, you’ll kink or otherwise restrict the flow through the tube. This goes for custom intake runners as well as exhaust headers, which is the topic of this month’s How To.
When it came time to make the intake system for my Corvair engine conversion, I had several hurdles to overcome. First, I needed it to be light. I was already pushing the envelope by installing a six-cylinder Corvair where a four-cylinder VW was specified, so I needed to save as much weight as possible, which meant my intake had to be made from aluminum. Problem was, I didn’t have the equipment or the skill to weld aluminum – that meant I had to take my parts to someone who could weld them for me.
I built this Corvair engine to be installed in a Quickie Q2 but never installed it or ran it.
The second issue was bending the aluminum tubing. One might think that the local muffler shop could bend the tubing to my specifications, but most muffler shops only have bending equipment that literally crushes the pipe as it’s being bent. The pipe wasn’t kinked, but the volume was reduced at the bends, which just wouldn’t do. But the answer was a simple one; mandrel-bent tubing with a consistently round cross section can be purchased in all common materials, diameters, thicknesses, and radii, and they’re not overly expensive.
I mail-ordered my pre-bent 6061 aluminum tubes – most being tight-radius, 180-degree bends – from Burns Stainless (Costa Mesa, California). With a 180, I could get virtually any angle from it and could usually make use of the other half.
Although I've never had a practical reason to get the “show” engine running, I built an engine test stand and have run a similar Corvair engine on it for research and development and to help promote the use of the Corvair. The intake system on this engine (yellow) is also made from mandrel-bent tubes from Burns, but I didn’t bother with aluminum, which enabled me to weld the pipes right on the engine.
So with the supplies in hand and the skill to cut and mate the pieces, the third issue was how to mock everything in place while building it and how to keep it in place while I deliver it to my welder without covering the welds.
The answer was rather simple and inexpensive. All it took were three short pieces of welding rod and two hose clamps per joint. I think it took eight clamps for my project.
All the work was done on the actual engine for which I was building the runners.
Prior to tack-welding each joint, I made sure of proper alignment for everything.
It’s best if the hose clamps are as close to the joint as possible, but space needs to be left for the welder to work.
Sharp eyes will notice that the length of the horizontal runners (after the bend) aren’t equal. That’s to compensate for the offset in the stock manifold logs’ carburetor placement. The Corvair heads are identical side-to-side, but the placement of the carb isn’t centered. This isn’t an issue in the automobile since each head has its own carb. By compensating with the unequal length of these horizontal tubes, the completed intake runner system is equal length, from the off-centered carb to each stock log.