I purchased my oil tank from GPR today. The Vellios comes with 3/4 NPT sized connections. I need to get my engine oil cooler (off a 3.0L SC) converted by Rich and he wants to know what size fitting to weld on. Am I correct to go with 12 AN? I've heard/read some use 16 AN?

Also, is there a list of what fittings and lengths of hoses are needed for all oil plumbing? Basic plumbing, no external oil cooler.

AN-12 = 6/8 or 3/4. I think 16's may be overkill unless it's a race engine. AN-16 stuff is harder to find and more $$$

the fitting on the cooler is the engine return.
it is gravity only
the most important one in the process

most people go AN16 on that one to make sure the gravity feed is flowing well.

The oil cooler line is an engine feed line. -16 is optimal, -12 is bigger than the factory lines. In addition -16 is a tightsqueeze. -12 ia a good compromise as stated above, unless its a race engine.

On your feed line, make sure you put a coupling about midway so you can drain/change oil easily.

Had two that required dropping the HE to drain the oil.

The factory had a split of the feed hose for oil change. I built a drain valve on my lines.....

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On my six I used -16AN and like above added a " tee " for easy draining. Just unscrew the cap and let the oil drain. I used -12AN for all other oil lines to the front oil cooler and return lines to the engine/tank.

But why use 16 AN when the bottleneck is the tank with it being 12 AN - 3/4ths?

Gravity feed vs...