For nigh unto four years. Bob Venners has been hoeing up dumps in pursuit, say of the exclusive Phoenix cone top or certain Pfeiffer flat tops.

Venners is a beer can collector, one of some 2,500 such kindred spirits who descended upon the beer producing capital of the world last weekend for the eighth annual Canvention of the Beer Can Collectors of America (BCCA).

But not just any cans will do for Bob Venners, a 36-year-old administrator in the Jackson (Mich.) school system. "Once you start collecting beer cans," he said, "you find out that you've got to start specializing. I mean, if you went after all the thousands and thousands and thousands of cans available, you wouldn't have room in your house for anything but beer cans.

"So what I try to do is, get one can of every type of beer made in Michigan, like Phoenix and Pfeiffer. Which keeps me busy enough."

At last count, he was 140 cans along toward the magic number of 185. All told, he had about 2,400 cans, counting a good number of duplicates and others, making him a "grand brewmaster," the highest rank that the BCAA can bestow upon a collector.

It hasn't been easy.

Venners, a stocky man with a raven ring of a beard, has driven his 1970 Chevelle to every dump within a 300-mile radius of Jackson and then done battle with snakes and rodents out there in the trash. His wife, Suzi, once picked up a case of poison ivy working the dumps with him, and now chooses to wait in the car until her warrior returns from the rubble.

To say nothing at all about police problems. "This one time, which was in broad daylight, I was walking around a dump and a squad car rolled up." Venners recalled. "They probably wondered what I was doing, which I don't blame them for. I started running toward them to explain: but, see, I still had the hoe in the hand, and one of the guys drew his gun. It turned out okay, but it was pretty sticky for a while."

Why does he risk so much?

"I guess maybe it's a sense of power . . . to have the best collection of anybody. I guess it's the drive to be the best that's behind the whole thing. I'm competitive and I guess it shows."

Bob and Suzi Venners arrived at the canvention in a rented van. The Chevelle simply would not hold the 1,000 empties they brought to trade.

The heavy trading was done in the cavernous East Hall of the downtown Milwaukee Exposition and Convention Center and Arena. Three miles' worth of cafeteria-style tables were arranged on the gray cement floor, and each tabletop sprouted with beer cans (most were empty, although there were a few full-can collectors). An estimated one million cans were on the premises.

People wandered through the maze as if in a daze: Perchance to spot a James Bond 007 can - a brand that never made it past the test market - or (dare one hope?) a 1935 Krueger, first beer to come out in a can.

Periodic PA announcements reminded the members that only trading was allowed, and that anyone seeing money changing hands should report same to the proper authorities.

The BCCA has always been adamant about this, as opposed to World Wide Beer Can Collectors, an organization that does permit the passing of the green.

The Venners had their display set up toward the rear of the exhibition hall. Perhaps 700 cans were out on the tabletop, either standing on end or lying next to one another, in sweet repose, in boxes; the rest were stashed in boxes under the table. While Suzi minded the store and worked on her embroidery, Bob set off in search of the Phoenix and Pfeiffer.

In his right hand, he carried a makeshift display case: a desk drawer with a strap handle where the knob should be. Inside the drawer were several shells, roping in 26 tradable cans. "Simple," Venners said, "but functional."

Down the line Venners did swap one of his Goebels (from Detroit) for a Paul Bunyan (from Waukesha Wis.) but nowhere was there a Phoenix or a Pfeiffer he didn't already have."I'd hoped for better," he said with a sigh and rejoined Suzi.

The conventioneers came from 36 states, Canada and even South Africa. Some didn't even drink beer but stayed in the organization because they like the other people. Occupations ranged from doctors to CPA's to truck drivers and fork lift operators.

A good number were teen-agers, or younger, perhaps proving the BCCA point that one reason for the popularity of beer can collecting was that it involved the whole family. Greg Coleman, from Deerfield, Ill. was only 12, but had been collecting for 2 1/2 years. "My friend's got me interested. It's where the action is," he said, sounding a good deal older than 12.

Clearly, the collector of collectors was John Ahrens, a publishing executive from Mr. Laurel, N.J. whose claim of having 11,000 different cans has been duly recorded in the Guiness Book of World Records. He started his hobby during the mid-'60's, when he was a history major at Yale, and hasn't stopped since. Adroll sort, he said he collected beer cans, "because it was such a worthwhile thing to do."