11-28-2019, 08:44 AM
Brad, there are certainly still issues with bolts. You can still use a high quality commercially made black oxide socket head cap screw in a stock or slightly modified engine. It's when you get to engines like Steve and Shawn Welte's or Jeff Brown's or Dave Bonbright's that you can get into trouble. The Bonbright screws have been very reliable, and reusable, but also are no longer obtainable. Unbrako brand SHCS claims a 190 KSI tensile strength in screws 1/2" or less in diameter. Holo-Krome screws have had a good rep, but are 10 KSI less in tensile strength. Unbrako recommends a 91 inch-pound torque for their No. 10-32 black oxide SHCS series. This is with a properly lubricated screw and a well calibrated torque wrench. The special Multiphase MP159A alloy that MS Aerospace used in the Bonbright screws is definitely available, and Dave B. still has the engineering drawings to make the screws, but until there can be a very great increase in demand, no screw manufacturer is willing to fabricate the screws. Several people have been working on the issue, but so far, the results have been less than spectacular. I have exactly one (1!) set of spline head early Bonbright screws left, and I am hoarding them! Use the Unbrako screws, but use them carefully, and REPLACE them EVERY TIME they are loosened. You also need a reliable inch-pound torque wrench. I'm sure the rest of the West Bend users have other ideas, but these guidelines work for me. Ted