I have a 396 big block 67 Camaro and recently installed console gauges. I have bought an oil line block fitting and was wondering what is the purpose of the nut and sleeve that comes with it? The oil line seems to screw straight onto the fitting. the nut and sleeve seem to serve no purpose.

 

Threaded fitting in the block. Slide nut on the end of oil line so threads face the fitting. Then slide the collar over the line. When all is together and the nut gets cranked tight, that collar crimps around the oil line to lock it in. Also, use copper line, not the cheap plastic one that can crack or melt which may have come with the gauge.

 

But there is already a nut on the end of the line that I bought. The additional nut and sleeve seem to serve no purpose.

 

consider it EXTRA. put it in your parts bin or throw it away

 

Put the sleeve and tubing nut in your 20-year parts jar.
If you don't have one, then start one and you might get 30-40 years of use from it.