Howard Rock lives in a mobile home, just west of the Van Winkle Expressway. The mobility is just an illusion, of course, because the house isn't going anywhere. But the notion that you could drive it somewhere is appealing.

Rock, 71, has been intrigued by motion most of his life. He built an airplane when he was 15 and then tried to fly it down Redwood Road. The thing never took off, a non-event for which Rock has thanked the good Lord many times since becoming somewhat more practical.Practicality is relative, though. There are people who think Howard Rock is still full of ideas that will never fly.

One of his ideas is The Cyclone Carburetor, which, when hooked up to another of his ideas, The Rockcycle Engine, will enable a car to get 80 miles to the gallon, according to its inventor.

Rock began working on the carburetor idea about 30 years ago. The machine has had several reincarnations since then, all of which he includes under the heading "Phase I." These appear, slightly out of focus, in an album he spreads out on the dining room table, along with Phase II. He has carved Phase II out of aluminum, a task that took him more than two months because he didn't have enough money for speedier tools. Phase I sits in a red 1974 Ford Ranchero parked in the driveway next to the mobile home.

Rock and Kelly, his 30-year-old son and partner, have high hopes for the Cyclone Carburetor, despite the fact that the Ford Motor Co. and the National Bureau of Standards have turned it down.

Though disappointed by their cold shoulders, Rock says he is not surprised. "If you knew how much money General Motors and the Germans and the Japs have spent on this, and then some `nut' out in Utah working in his back yard comes up with something . . . " he says to explain their lack of confidence. "They're not going to listen to it."

Besides, he says, "People who aren't thinkers don't know what I'm talking about."

The beauty of the Cyclone Caburetor, says Rock, is that it creates a totally homogenized mixture of gas and air. As a result, he says, the Cyclone eliminates polluting exhaust products such as nitrous oxide, uses less fuel, and runs at much lower temperatures than normal carburetors. In fact, he says, it feels cool to the touch even after the engine has been running an hour.

Noel deNevers, professor of chemical engineering at the University of Utah, is hardly impressed. "There have been a hundred thousand patented carburetor ideas," he notes wearily.

As for Rock's claims, deNevers dismisses them as "nonsense, nonsense, nonsense." An equally skeptical A. Lamont Tyler, chairman of chemical engineering at the U., goes a step farther."Absolute nonsense," he concludes.

Not everyone is as pessimistic. Rock produces several encouraging letters from engineers in different parts of the country who have either read his proposals or visited Utah to see them first-hand.

"The evidence, gathered from your project, strongly indicates a new carburetion technology has been uncovered," writes Lawrence W. Cerenzie, a former ARCO Oil and Gas design engineer now living in Alaska.

At "pretty near 72," Rock has a weathered face, is missing a couple of teeth and sounds like a Bartles and James commercial. His right arm is only partly useful, the result of a run-in with a '29 Packard many years ago. He has no degree, no resume and little marketing savvy. In short, he's just the kind of underdog that would make a great folk hero if, years later, it turns out that his inventions are sound.

Howard Rock quit school after the eighth grade. "But I have a terrible curiosity," he says. "And my son's got it. We can't sit still for repetition."

Rock thinks time will prove him right. He is hoping that some wealthy investor will put money behind his patents, which include, in addition to the carburetor and engine, a new dredging technique that he figures will make America rich.

The dredge, he says, can mine iron ore at about $2 a ton rather than the usual $30. His son, he says, has developed a process that can then separate titanium and other rare minerals from the iron ore, also much more cheaply. All this will have a big impact on American manufacturing, he says.

He says he has been gypped out of enough money over the years "to have done several other inventions." He has built about a dozen dredges, selling each one to people who turned out to be more interested in selling stock and buying fancy cars than in developing his ideas.

Rock estimates he has spent $1.2 million of his own money on the dredge so far, and about $100,000 on the carburetor. Some of the money came from another of his inventions, the "Econojet," which was designed to increase gas consumption and reduce pollution. He says he sold 300,000 of these.

He hopes now to raise $1.3 million for Phase II of the Cylone Carburetor. "The problem is," he concedes, "that being so unbelievable and needing so much money, we can't go through normal channels."

And if he spends all that money and Detroit still doesn't want his ideas?

"We'll make our own cars! Why not? The Japs did it."

Rock fell in love with cars after seeing his first one, a model F, when he was five. When he was 20 he won the treacherous Widowmaker Hill climb. About that time he also started racing midget race cars at the fairgrounds, and later, with his wife, he built the old Hippodrome racetrack.

These days, the main thing he races is his mind. "I want to live to be 150," says Rock. "I have that many things in the works."