I have a couple of choices of oil fillers to use with my aftermarket oil tank. There are notable differences and I’m not sure why.
One is aluminum, the other steel.
Overall length. The aluminum one is a bit longer which could make filling easier. But more intrusive.
The vent hose sizing. Aluminum one is for 25mm hose the other is 13mm. I’m guessing they are designed to terminate at different devices? I’ve seen from diagrams that some end at an oil overflow bottle. Where did the hose end up on the original 914-6?
Thanks for your help.

It's been a while since I owned a stock 6 but if I recall the oil breather hose from the filler neck went to the triangle of death breather tube on the engine.

I have a 3.0 sc motor. Trying to think where the Triangle of Death resides.

You should use the one with the larger vent, the 25mm is the same as engine breather, oil tank, and where the hose attaches at the air intake, at least on my 2.7 cis.

I have a 914-6 air filter box. I’ll look there to see if there are any 25mm connectors.

Mine is the one in the bottom of the picture. The smaller fitting is for a puke tank this the small fitting and would be the same size as the GT fillers necks. The 1” fitting on the aluminum filler is meant to connect to the stock air filter. The 1” fitting on the tank should connect to the breather near the triangle of death.

Btw why you really don’t want the vent to connect to the air filter is that when you accidentally overfill the tank and that’s a when as everyone has done it at least once or when you drive aggressively the excess oil gets consumed by the engine and you get a ton of smoke out the tail pipe which will also effect combustion effect and could be detrimental to the health of the engine especially if running full tilt. Stock -6 engines really were not high performance so didn’t really matter

Simple answer mine is designed for puke tank just like GTs

The aluminum one designed for attaching to stock filter but could be adapted to puke tank.

Been their done that. I thought my 3.2 engine died, but I accidentally over filled the oil tank during an oil change. I installed a puke bottle after that fateful day.
I have a stock 914-6 filler pipe, but a smaller, less obtrusive hose would be nice to the puke bottle.
Click to view attachment

Thank you. This information is very helpful.

For reference the upper one in the picture is PMS brand.