As with all '66 Corvairs, the 500's frugal tendencies stem from its power plant. Besides being pinch- penny to drive, the air-cooled rear engine scoffs at radiators, antifreeze, water pumps and winterizing expenses. Also, engine-behind design makes possible Corvair's virtually flat floor (there's no transmission tunnel); convenient front luggage compartment; and the kind of traction that lets you take the beaten track or leave it

Does 500's low price mean we've skimped in re- fining its hardtop styling? Decidedly no. The flush-mounted windshield and rear window are framed in bright metal, and the body front emblem and 500 nameplates are brand new. New taillight look and backup lights add to the standout value.

In the best 500 tradition, the roomy all-vinyl interiors are pleasing to the eye and, for all practical purposes-people-proof. (With easy-to-clean vinyl, there's no need to worry about things like soggy bathing suits.) Trim is offered in fawn, red and blue. Seat upholstery: vertically ribbed pattern vinyl with textured vinyl at the center and sides.

Door panels display a two-tone treatment. You'll also find chrome control knobs and trim on the padded instrument panel, all-rubber floor mats and color-keyed plastic cowl side panels. (Those last resist scuff marks from shuffling feet and contain ventilation grilles for cooling the same.)

Here are more 500 likeables, all standard: weather beaters, like a forced-air heater and defroster, windshield washer and glare-reducing two-speed wipers, padded sun visors. Easy-care features, like a long-life exhaust system and self-adjusting brakes. And comfort makers, like the foam- cushioned front seat and front door armrests. Plus cigarette lighter, coat hooks, interior lights, lockable glove box.

Pick either the 500 Sport Coupe or Sport Sedan and equip it with one of a selection of nine power teams. Either model stacks up as an ideal way to have a ball on a budget.