I second Grigg's response. Get a banjo fitting and screw it in the cylinder, it should solve your problem. No telling what has been installed over the years, but more than likely it was just something to keep it on the road.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine