I just replaced my blown motor with a differant one that had 60K miles on it, an 87' N/A. The clutch looked good and the pedal feels like a good cluthch but it slips bad with a shift hard or dump it. All I have is a ported intake and full exhaust so I do not think that it is to much power or is it? I have a performance clutch on teh way but I did not want to install it until I put in my rebuilt street ported motor in a few months. Any suggestions? Oh, it did do it really bad and it got better this only the second day that I have driven it so coudl it be it just has to seat or burn off some grease?

 

As long as there is play between throwout brg and presuure plate, grease could cause slipping, however I would be more inclined to believe a weak pressure plate. Weak springs just don't exert enough pressure, or sqeeze the disc tightly against the flywheel.