I bought an '86 Blazer that had a new Jasper 2.8L V6 installed in 07. The problem is oil is pumping into the cooling system...previous owner said the intake manifold gasket needs replaced...new radiator, new hoses new thermostat and about $9000.00 worth of work he has done to it..I have all the receipts..I wanted to test it myself so I topped off the coolant system and the oil was full...looked brand new...at start up it cranked over and started but had a backfire popping coming from carburetor..engine seemed to have good compression..could the intake manifold gasket failure cause the oil in radiator..and the backfire be a miss adjusted valve or sticking valve? Also there is no coolant in the oil.