My '88 first started leaking around 80K miles, and not very badly. I lived with it until around 100K when I changed out the head. That was last July, and another 5K miles since then with no leakage.

Make sure yer not over tightening the hold-down bolts, and like Richard sez, check the cover carefully for defects.

C/YA!
Jeff
'88 Trooper
2DR LWB 4ZE1 5SP
bone stock DD