Bleach

Replace your timing chain and put the bright links on the proper marks on the cam sprocket and crankshaft sprocket as mentioned in most any 280ZX manual. (Haynes is good enough and really cheap on eBay)

Then insert the oil pump properly so that your distributor lines up where it should at cylinder #1 when the engine is at Top Dead Center on the compression stroke. Your distributor should be at the very "center" mark of the manual adjustment nut with a new timing chain. Use a timing light on the front pully to verify that your timing is 10 degrees before TDC. If the timing is way off, then most likely your oil pump was inserted wrong and is off by one tooth or more. Re-insert the oil pump and distributor to correct the problem.

Also, make sure you have a good distributor that has a functioning vaccumme advance system and that the rotor's lower bearing is spinning free and not binding.