[Heavytruck]

Here's what I have on this subject. My 02 van, 5.7 l31. Leaking down back of block. Intake gasket. The factory gasket is plastic with silicone rings around the ports. I spoke with a tech at fel- who also had been an engineer at GM. He told me that in a truck application the block flexes too much and the gasket leaks possibly even cracking, the dexcool gets by even pitting the aluminum. The engine vibrations even will wear ring grooves around each port. If excesive, the heads need removed and machined. Felpro makes an improved truck gasket, steel sealed in a silicone rubber, and anti-crush spacers at the bolt holes.....My 99 grand prix, no external leaks, just lots of smoking. It seems as though the antifreeze had pitted an area where coolant flows through the plenum via near the throttle body.I replaced the prenum to intake gasket and plenum to throttle body gasket, as well as oil and coolant system flush. All better now. i hope this helps.