1piece to 3 piece cranks kit5/30/2023 ![]() We installed the test seal in the accompanying photos on a 1000+ horsepower big block Chevy and found no leakage after 27 dyno pulls and a half a dozen passes on the car. The BBC seals are being used in race engines at 25.0”Hg vacuum without problems & dyno tests have verified that the engine can produce both extra power & increased torque after fitting the F-Type Seal. The seals have been in use for almost 4 race seasons without problems, and many users have advised that the seal solves all of the basic problems with the two piece seals i.e. ![]() It has been test with extreme angles and still works properly. The cut does not have to be made with any particular precision. ![]() When installed the cut surfaces match perfectly and no sealant is required. A further advantage of the seal is that it only has one joint face which is installed towards the top of the engine for maximum effect. Being bi-directional the seal can also be used in Marine engines with reverse rotation. The oil control lip incorporates their highly efficient HD2 Bi-Directional Hydrodynamic helix feature which reduces seal drag & improves sealing reliability. The flywheel side incorporates a bonded PTFE facing which holds crankcase vacuum without raising friction. This enables the seal body to be opened & twisted around the crankshaft flange before the main bearing cap is installed. Before assembly the seal is cut radially in one position using a very sharp blade. The 1-pc seals are designated “F-Type” because they have built-in flexibility which enables the seals to be opened out around the crankshaft. While this seems extreme, it is in fact a brilliant solution. This one piece seal from GST RACING SEALS TM is designed to be cut and twisted around the crankshaft for installation. For several years now a new type of rear seal has been making the rounds of racing engine builders with great success. And many builders still incorporate a small bit of non-hardening sealer on the parting surfaces, but it is still a craps shoot even for experienced builders. We all know the time honored method of offsetting the seal parting lines so they do not match the main cap to block interface. ![]() Some engine builders, such as Keith Dorton of Automotive Specialists, who walked us through this installation process, produce their own with round stock on a lathe, but you can also purchase one from CV Products (PN CV925).Rear main seal leakage remains a problem on engines that still use 2-piece rear main seals. In addition to the adapter plate-available from GM (PN 10051118), Canton (PN 21-850), and many other manufacturers-a small fixture to simulate crankshaft location is required when performing this conversion. No major machining operations need to be performed on the block to get the adapter to fit. The adapter makes it work with popular aftermarket crankshafts, oil pans, and other components. Thankfully, it's relatively easy to convert a block from a one-piece rear main seal design to the older two-piece style with an adapter. The aftermarket, such as Dart or Motown, still produces small-block castings with the two-piece rear main seal design, but they tend to be more expensive than the stock blocks GM sells. GM recently sold the last of its block inventory with the two-piece design, and there are no plans to cast any more.
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