Ok, first off I have a 90 GXL I just got done installing a rebuilt engine. When I go to start it up the there is a vaccum leak. I think the leak is either at the intake maniflod between the engine block and the manifold or between the upper and the lower intake manifold. I have not tested yet. I think my problem is with the gasket(s). I put them on dry. would i be able to put some silicone on the gaskets to seal the leak? When i got the engine the directions said to put the gaskets on dry, so i am thinking that it might be bad to put silicone on the gaskets.

 

i do not advise people to use silicone on or around intake gaskets. just make sure all mounting surfaces are smooth and clean, then torque the bolts to spec.

i usually use a razor blade (single edge) and carb cleaner or oil to get the suface clean. then go over it VERY gently with really fine sandpaper.

on those 13B intakes, it's also very, very, very important to make sure that you do not over-tighten the bolts. the lower ones WILL crack the manifold ... and trust me, you don't want that kind of trouble!