The NS300L™ system was designed not only to be the strongest, most reliable repair on the market, it has also been designed from an economical stand point. This was accomplished by standardizing the outside thread of all the inserts we have available, eliminating the need to purchase a separate kit for every head bolt size. Inserts are currently available in M10X1.25, M10X1.5, M11X1.25, M11X1.5, M11X2.0, M12X1.5 AND 7/16-14. Call for details

The photo shown is for the Cadillac Northstar. The only variation from other kits is, the quantity of inserts, insert length and internal thread size depending on the application. All other components are as shown.

The photo shown is for the Cadillac Northstar. The only variation from other kits is, the quantity of inserts, insert length and internal thread size depending on the application. All other components are as shown.

   The NS300L™ insert also allows you the option of using the properly engineered OEM head bolts, or if you prefer, high quality studs such as ARP® . Both are well engineered with rolled threads to prevent fatigue failure (rolled threads are about 15-20% stronger than cut threads). They are also engineered with the correct physical properties to allow them to stretch and contract as the engine heats and cools (similar to that of a very heavy spring), helping to keep a constant amount of pressure on the head gasket during its heat cycle. This is vital for a long term repair. This is especially critical when mounting an aluminum head to an aluminum engine block given the high expansion rate of aluminum, which is much higher than that of steel. For this reason, be very cautious of repairs that use anything other than a solid thread repair along with factory head bolts or high quality studs such as ARP®. There is absolutely no credible data supporting any mechanical advantage to other repairs. Some repairs often do not have the correct physical properties of OEM head bolts or quality studs such as ARP® brand. Using a fastener without the correct physical properties can result in a more rigid, less durable repair that could lead to head gasket failure after several heat cycles. Rigid is the enemy of a long term successful repair, especially when fastening an aluminum head to an aluminum block that will go through many heat cycles.

    If you choose to use head studs rather than head bolts, please contact us so that we can help you determine the correct stud for your application. The studs that your engine calls for may not be the correct length when used with our inserts since our inserts many times are not installed to the same depth as the original factory threads.