Originally Posted by lowhirod
I am trying to put a GM vortec TBI intake on a set of 60979 Edelbrock vortec heads. My problem is the intake has 3/8 inch bolt holes. the heads have 5/16 holes? is this allright? the intake part no. is 12496821 preformance intake
Use a hardended washer between the bolt head and the intake. The larger hole in the intake is to accommodate the various assembled part dimensions resulting from decking the block and/or milling the head. The hardened washers are available at hot rod shops and speciality fastener stores. These provide enough strength to bridge the gaps between bolt and hole without bending and their stable surface that doesn't damage the soft aluminum of the manifold by allowing the bolt head to distort the washer to where it crushes into the soft aluminum.
My preference when bolting into aluminum is to either use stainless steel or plain uncoated steel with an anti-seize lubricant or a teflon based sealer such as plain old fashion plumbers Teflon sealer from the local hardware store. Be very careful of any thread lubricant or sealer on blind threaded holes as any uncompressible compound caught between the bolt end and the bottom of the hole will crack or blow out the casting. Galvanize and zink coatings are very chemically reactive and are likely to corrode the aluminum threads if any moisture gets in there which is why I don't use coated or plated harware in aluminum except for chrome plate which isn't innocent either but isn't as chemically aggressive as zinc.