Is this a Chevy smallblock? Before you freak out, you should know that the gen 1 Chevy small block and its derivatives have wet intake manifolds and will burn coolant because of a failed intake manifold gasket. This is fairly common with engines from the 'Vortec' era just before the gen III engines became common and the fix is a properly installed Felpro gasket. And all kinds of weird shit went down around the same time because of the switch to Dexcool.