EngineQuest SP300E Ford 300 CID Smog Plug 1/2-20 x .55

The EngineQuest SP300E smog plugs are designed specifically for Ford 300 CID pre-'84 engines, providing a professional solution for sealing air injection system ports in cylinder heads. These precision-threaded plugs feature 1/2"-20 thread pitch with a .55" length, making them ideal for blocking off the ports left behind when removing secondary air injection equipment.

Key Features:

• Thread specification: 1/2"-20 x .55"
• Sold in convenient 10-pack sets
• Engineered for Ford 300 CID (4.9L) inline-6 engines manufactured before 1984
• Also compatible with Ford V8 engines: 330, 360, 361HD, 390, and 391HD applications
• Proper thread pitch ensures secure, leak-free seal
• Made in the USA by EngineQuest

These plugs allow you to cleanly remove the air injection rails and associated smog pump equipment while maintaining proper sealing of the cylinder head ports. The plugs seal the exhaust air supply rail ports left in cylinder heads equipped with the Thermactor emissions system. The correct thread specification ensures the plugs can be installed and removed as needed, allowing the vehicle to be refitted with air injection equipment if required for emissions testing. Each plug is precision-manufactured to fit flush and provide clearance for aftermarket headers.