The valve is not a modified Crosman valve, it's re-designed for maximum power and consistency and machined from 7075-T6 aluminum bar stock. We are the only company in the world producing a completely custom re-engineered valve for these models.

INSTALLATION INSTRUCTIONS ARE POSTED ON THIS PAGE https://magnumairpower.com/ols/products/custom-valve-piston-kit-for-crosman-1377-1322-1300kt-drifter-2289g-pc77

 The valve-halves can be rotated to either side to align perfectly with the port and mounting-screw holes in the pump-tube which are often not square with each other from the factory. The factory valve and custom valves sold by others aren't designed to allow this because all of them are factory valves, modifications or not. The valve body has a larger ID, the cap is larger ID with shorter threads and a deeper chamber, the valve-stem seat is further back which allows the pin on the valve-stem to stick out a little further so it has a longer throw. The combination of all these enhancements means it can hold more air than any other 13XX custom valve on the market. Due to the pin on the stem sticking out a little further and the short angled port it empties faster and more completely with less hammer force. It's the same outer dimensions as a factory valve. The exhaust port is radically angled to produce more power. Because it's angled the opening looks oval rather than round, this is not by mistake, it's supposed to be this way. The transfer port gasket fits and seals effectively with the .150" ID of the port, do not enlarge the port ID, it will not seal with the gasket correctly if you do. Further enlargement of the valve port will not gain more power, matching your transfer port and barrel port to the same .150" diameter will at higher numbers of pumps.

The custom piston pin is machined from tool steel with radiused ends to match the internal tube contour, this reduces scoring and makes pumping smoother. The piston head and locking collar is machined from 7075-T6 aluminum, one of the strongest of all commercial aluminum alloys, stronger than many types of mild steel and stainless steels only much lighter. The piston-base is machined from Delrin for ultra-smooth function and to act as a compression-buffer to help protect metal parts from excessive stress. The piston rides on the Delrin base and cup-seal with no metal-to-metal contact to reduce scoring, wear and work smoothly. The cup-seal produces a shot to shot consistency generally within 4-5 FPS which greatly enhances accuracy, almost as good as our flat-faced kit, but with much less maintenance, especially in dusty or dirty environments.

 These parts work well at 4-17 pumps. Other sellers advertise kits that allow you to put 30-40 pumps into their valves, this is due to their valves needing 30-40 pumps to equal the power of our custom valves at 15-17 pumps.