![]() This occurs because the threads on both the tapered pin and hole have an interference fit. Sealer really is not necessary, but is often used for added insurance. The holes for tapered pins must be carefully hand tapped and the pins hand tightened for a tight seal. Straight pins are faster to install because an ordinary tap and power drill can be used to install them. Straight pins are designed to twist off when tightened, eliminating the need to cut or grind the heads off (as is necessary with tapered pins). Straight pins also have an interference fit over their entire length, and a tapered shoulder that crushes into the surface. This eliminates a thread line on the surface enabling the surface to be machined. This type of straight pin can also eliminate the need for installing valve seat inserts in cast iron heads. Various types and sizes of crack repair pins and plugs. Ordinary tapered and straight pins cannot handle certain kinds of cracks, such as those along an outside edge or corner that require support to hold the sides of the crack together. The same goes for cracks in an area of a casting that would open up or pull apart when the casting is under load or gets hot. For these types of crack repairs, locking devices and/or pins with a self-gripping ability can provide the required reinforcement and strength. You must pay close attention to the depth of the spotface to make sure there is enough material left for threads."Castmaster" pins (manufactured by Lock-N-Stitch) have a unique "spiral hook" or "reverse pitch" thread pattern that grips both sides of a crack when the top shoulder of the pin bottoms against the metal. In the combustion chamber this will make the repair more heat-resistant. Whenever possible you should try for approximately 50% of the shoulder to be left below the surface. NOTE: The spotface depth for C Series pins is important. The sealant will lubricate during installation and then cure for retaining strength. You can simply apply LHC623 to both the seat bore and seat and drive the seat in the way you would in a cast iron head. When seat inserts will be replaced after a crack repair it is not necessary to heat the head and freeze the seat prior to installation. Aluminum CASTMASTER® pins should be used in combustion chambers when cracks extend below valve seat inserts and when the inserts will be replaced. Steel CASTMASTER® pins can be used in aluminum castings where heat and corrosion are not a factor. It is often easiest to use L Series pins next to the locks and then continue the repair with C Series pins. In extreme structural repairs, locks should be used in conjunction with CASTMASTER® pins. These changes include a single tap process for through holes, same tap drill size as L6 pins, a hook angle under the shoulder with matching spotface, ability to be used in thinner sections and a large increase in strength and seal. Many improvements, including one of the original design features, have been included in this new version. ![]() For sections starting at 0.200" in thickness, use C2F pins and for sections 0.750" to 2" use C3 pins.Ĭ2 was the first CASTMASTER® pin introduced and is now is being replaced with C2F pins. For repairs in thin sections down to 0.100" use C1 pins. You should always choose the largest diameter CASTMASTER® pins that you can. Cracks that originate from the corner of the cap fit in a main bearing can be repaired with C Series pins. Cracks that extend from threaded holes, freeze plug holes, pipe plug holes and main bearing holes require CASTMASTER® pins. C Series pins will seal on both ends.Ĭracks that run crosswise on the top of cylinder heads are usually repaired with CASTMASTER® pins in order to add strength instead of spreading pressure, so the repair will not open when the head is torqued to the block. Cracks that extend back into a port are repaired by drilling through both walls. A new seat can be ground or three-angle cut right on C Series or L Series pins. C Series pins can be used from the bottom of the seat angle outward to the end of the crack. Because of the spotface, installing the pins at steep angles to the surface usually doesn't leave enough material thickness for the threads.Īlmost all repairs to cylinder heads that are made below the seat angle are made with L Series pins. The reasons not to choose C Series pins for all your repairs are cost, speed and technical requirements. The spotfacing is accomplished with a special piloted tool. So why not just always use CASTMASTER® pins? The installation process requires that every drilled hole receive a recessed spotface to assure some of the shoulder of the pin remains below the surface after grinding or machining. This pin with its incredible Spiralhook™ threads creates a drawing pressure that actually pulls the sides of a crack together and permanently locks them together. CASTMASTER® (C Series) stitching pins do not spread the crack! In fact they do the opposite.
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