Clark scored just before halftime to decide a lively contest in which the teams combined for 28 shots and numerous near-misses. Forty-three players took the field, with only Dynamo defender Pat Iannigoing the full 90 minutes.
Said San Jose coach Frank Yallop, "It was a good start for us. The guys put forth a good effort and we created some good chances to score, especially in the second half."
In that second half, Shea Salinas, Matt Taylor and Yuri Morales all tested Houston keeper Tony Caig, but he turned them away with sharp saves. Caig had replaced regular starter Pat Onstad at halftime.
Clark scored after a penetrating pass from Dwayne DeRosario triggered a scramble in which Chris Wondolowski centered a ball that Clark drilled past Quakes goalkeeper Joe Cannon.
The teams play again on Saturday in San Francisco. Houston is using the two games as preparation for the Pan Pacific Championship in Hawaii next week. After Saturday's match, San Jose will play Columbus and D.C. United in San Luis Obispo.