my 84 GMC sierra 1500 had a crated motor installed in 97, along with hedders,alum intake etc. about two or three monts ago it started to guzle oil ( a quart every 500 miles). it just about drove me nuts trying to find the cause. i took my truckin to have some other work on it and the mechanic said he wood check out the oil problem too. come to find out it has a cracked intake manifold gasket. gasket replaced,problem solved.