EAA Sport Aviation - April 2010

One of the things we learned that we’d like to pass along to anyone trying to get tight, even-fitting doors is to make sure you have the engine, or equivalent weight, hanging on the mount, because fuselages flex. They don’t flex much, but enough that your doors probably won’t fit if you minimize the gaps without that weight in place. We found that out the hard way.

We had hoped we’d be able to fly without headsets, but when we put one of the better muffler systems on it, we found it generated too much heat and was threatening to scorch the cowl. So we went back to straight pipes, which are much louder but at least they make the airplane lighter and faster.

Dan and Bill chose a 72-inch MT electric constant-speed prop.

While fitting the doors they changed the geometry of the gas strut arrangement so that it was pushing in such a way that doesn’t try to flex the door. At the same time, they stiffened up the doors so they can now taxi with them open and not worry about them being damaged.

on the dash with ‘lean’ and ‘rich’ lights that lets you fine-tune the system in the air.

Another little hint…when installing the hydraulic system and lines for the retractable gear we found out quickly that hydraulic fluid looks exactly the same as a wetted-out lay-up so you can’t see the leaks very well. So, we painted all of those surfaces white to make the oil stand out immediately. We also modified the gear mechanism slightly to prevent the cables from jumping off the pulleys. We found that out the hard way, too.

Originally we were going to go with a turbo’d V- 6, but we couldn’t come up with an ignition system that would give us the backup that we were satisfied with. The next move up, which would add 60 pounds but give access to a world of proven equipment, was the aluminum small-block Chevys [SBC]. I had one sitting in the shop, so we put it up there to see if the outside dimensions would fit, and it was a little tight, but very doable. So we went the small-block route.

When Bill said “small-block Chevy” everyone knew what he meant, and most thought the displacement would be around 350 cubic inches, since that’s the quintessential Chevy V- 8. Bill and Dan, however, wanted the name Velocity to really mean velocity, so they went a slightly different route.

The ignition uses dual pickups, and the primary ignition is an Edelbrock MSD ‘off-road’ unit. Paul Bergholtz, our tech guy, suggested that for the backup ignition we use an entirely different unit, specifically the Crane ignition box, so we wouldn’t be running two systems that have the same weak point. We have another knob on the panel that lets us change the ignition parameters, so between that and the mixture control unit we can really get the fuel burn down and the power up.

When they were doing the basic airframe, they kept an eye on future maintenance and tried to provide easy access wherever possible.

One of the real problems with running auto engines is coming up with a reduction unit that doesn’t cause more problems than it solves. And the CheVelocity guys had their share of problems.

Among other places, we put a big access door in the nose, so we can pull a lever and have a lot of systems, like the gear system, filters, etc., right there in front of us where we can service them.

The big challenge on their airplane obviously was the engine. At the time they started the project, there were a few Velocitys flying but none with a Chevy, so they had to pioneer their own path.

There is a wild little aluminum
block, called the Dart Aluminum Rocket
block that is used in Can-Am racing, in
which the oil pan rails are widened 1 inch
and the cam is raised in the block high
enough to allow a much bigger bore and
stroke. So, what you have is a whopping 427
cubic inches in a block that is the same size
as any other SBC, and the same weight. It’s a
block the racers love, so there is tons of rac-
ing stuff available for it. It has a
four-and-one-eight bore, and a 4-inch
stroke-billet steel crank from Eagle with
6-inch-long Trick Flow mid-weight rods.
The cam was ground custom by Crane, and
it’s running tuned port injection [TPI] from
Edelbrock. The injection system has a dial
(with not a lot of enthusiasm) We
bought a kit from a well-known supplier, and
it looked okay on the surface. We got it
together and on the airplane, and it lasted a
total of eight hours. I was on takeoff and felt
a strong vibration, so I chopped the power
and aborted. When I coasted to a halt the
propeller was freewheeling: it had broken
the input shaft. Dan and I looked at each
other and said almost in unison: ‘We can do
better than that.’