The Washington Bullets agreed yesterday to give the Detroit Pistons their first-round draft choice in 1980 and another in 1982 as compensation for their signing of free agent guard Kevin Porter.

The Pistons had hoped to receive at least one player from among Mitch Kupchak, Greg Ballard and Larry Wright from the Bullets for losing Porter, who set a National Basketball Association assist record last season. But Detroit settled for the draft choices.

"I think we came out so good because Detroit just couldn't get anything better," said Bullet General Manager Bob Ferry. "Kevin wanted to play here so it was in Detroiths best interest for him to come here and get what they could for him."

It also was learned yesterday the Bullets probably will receive at least one first-round draft choice from the Houston Rockets as compensation for Tom Henderson.

None among the Rocket, Bullets or Henderson's attorney, Scott Lang, would confirm that Henderson had signed with the Rockets. But NBA sources said the signing is imminent and the compensation already has been worked out.

The addition of the high-stepping, crowd-pleasing Porter, who was known as the "Little Drum Major" when he played in Washington from 1972 through 1975, is expected to make the Bullets a more exciting and a stronger team.

"I think we're a better team right now than we were at most any time last year," Bullet Coach Dick Motta said yesterday from his offseason home in Fish Haven, Idaho.

"I think Elvin (Hayes) and Bobby (Dandridge) will have as good as, or better years than they did last year, and the fast-break baskets and cherry picking we get from Kevin will make us a more exciting team.

"I don't want to gush so much that it makes Tommy (Henderson) look bad, because he did a good job for us. We won a world championship with him. But to lose your playmaker and come up with a prize like Porter to take his place has to excite you. I'm having a tough time right now not getting too excited.

"I remember as soon as the season was over I told Bob (Ferry) that I didn't want to go to camp with the same team we had. I thought we needed something new. And boy, we got something new. The boredom will be gone from camp now.

"We've gone through some changes in my stay here and we've progressed to different levels. The addition of Kevin should bring us to the highest level yet.

"We were floundering at guard with Phil Chenier and Dave Bing when we brought Tom in, and he brought us up to a certain level. There's no question about his contribution.

"Kevin should come in and bring us to yet another level. He should fit right in with everyone, especially Dandridge because we just didn't get the ball to Bobby enough for that little shot of his from the side. We will now."

Ferry, the man who worked out the Porter deal, said the Bullets' success next year will depend on "how much more valuable Porter will be to us than Henderson was, and nobody can answer that right now. It just gives us something more to get excited about and getting excited is good and healthy."

Porter translates into a lot of easy Bullet baskets to Ferry. "We'll be sneaking down court again," he said. "He gives us the little extra. We are a very workmanlike professional club and Kevin will give us something we need - a little soul and a little life."

With Porter in the fold and Henderson on the way to Houston, the only Bullet question unresolved concerns Kevin Grevey.

Grevey is a free agent, but Ferry said the Bullets want him back. Grevey's agent, LaRue Harcourt, said Grevey wants to return to the Bullets and he is optimistic things will be worked out.

Assuming Grevey does sign with the Bullets, Motta will have a serious roster problem. The Bullets will have 13 players under contract, and they can carry only 11 on their active roster.

Not counting Grevey, the 12 Bullets now under contract are guards Porter, Wright, Chenier, Charles Johnson and Roger Phegley; centers Wes Unseld and Dave Corzine, and forwards Hayes, Dandridge, Ballard, Kupchak and rookie Steve Malovich.

Next session's starting lineup is set at four sports with a battle expected among Grevey - if he signs - Chenier and Phegley for the big guard or shooting guard spot.

Grevey is a fine shooter, but limited otherwise. Phegley is an untried second-year player who also is limited and Chenier is a former superstar trying to get his game back. He currently is playing in the Urban Coalition's summer league, and if he returns to his form, he could emerge as a starter.