I Have A 1978 Datsun 280z Thats Been Sitting For A Year Cause I Blow The Motor. I Just Put A New Motor In This Weekend And Now My Clutch Is Not Holding Pressure. Like I Have To Pump Up The Pressure Just To Get In Gear. Once I Pump Up The Pressure An Get Going Once It Time To Change Gears I Hit The Clutch To Go To The Next Gaer It Want Go. But It I Roll Down The Street An Pump Up The Clutch It Will Go Into Gear.
All My Fluid In Right An I Have A Brand New Clutch.

Somebody Please Help Me
Thank You

 

I also have a 280z and I pulled the motor and now it does the same thing yours is doing. My buddy told me it might be the master cylinder for the clutch.

 

I got mine fixed. All u have to do is take the master cylinder off and pull it apart and clean it. I tried it on mine and now it works fine. It jus had brake fluid on the seals I cleaned it all out and it works fine.