I have a 87 Z28 w/ a 350 rebuilt from a 85 corvette.I tried 3 diff. types of valve cover gaskets and still leaks on pass. side rear causing light smoke.I do have chrome covers w/ a breather on pass. side and a PCV on driv. side.All sensors, Ecm, and Prom are for this car w/ the 350 install.Also has coolant leak from t-stat gasket/housing.I replaced w/ new t-stat and gasket and still drips?No cat , flowmaster ex. , 24lb. inj., perf. prom, 180 t-stat, no screen MAF, coolant hose to T-Body delete, mild cam, manual cool fans, and 2 new K&N filters.Also throttle response is a little awkward (slow??) I believe w/ weak feeling at higher RPMs. PLEASE HELP ME GET THIS CAR GOING!!!!!

When I got this car----Had to repair 37 wires (mice) change all 305 sensors,prom,plugs, etc to 350, re-route all vac. lines,batt., and repair 2 bad grounds???? This is driving me C R A Z Y! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

 

I'd suspect your valve cover is warped. You might want to try other ones or put a bead of silicone on both sides of the gasket next time. Make sure all the surfaces are clean (I use lacquer thinner). Same for the tstat housing.

As for the running problem, it's impossible to diagnose without runtime data from the ECM. It could be lots of things. Any codes?

 

No codes, new valve covers (they are chrome orig. gone when I bought it), gaskets, w/ silicone top and bottom of gasket.Also used brake clean to clean surfaces. Thanks for reponse!!!! I m heading over to parents now to give them a hand w/ new dog.I ll be on later though.