Oil pan drill and tap or punch and tap

[JonMcCann13]

Ok before I destroy my oil pan

after researching I found two methods of putting a drain line on the oil pan

Drill and tap the oil pan using appropriate tap and drill. Mine happens to be a 3/4 npt tap.

The other is to punch the pan using a plumb bob and then tapping using a tap.

So which method do I use and when I'm done do I jb weld the end to make sure it don't come out

[marc79euro645]

Oil pan is cast aluminum, Do not Punch, it will crack.Use loctite or rtv to seal tapped threads.

[JonMcCann13]

Thanks very much. Is the 3/4 too big or will it be fine

[Cjames570]

Did you not research a method of actually welding a bung on? It's the obvious choice...

[Brad D.]

Definitely don't punch the pan, that only works with sheetmetal and will only crack the cast aluminum. Drill and tapping work fine as long as you make sure that you drill above the windage baffles (I suppose this also goes for welding, but since its off, it's easier to see where you can and can't drill). Also, I drill and tap mine with the old engine oil still in the pan. Once it's drilled and tapped drain the oil, flush a couple of quarts of cheap stuff through with the drain plug out, refill and drive on.

[mitch5]

I just went through this, depending on which pan you have it might be better to weld a fitting on the timing cover for a drain. My b35 pan is full of oil all the way to the top on the side you need to tap.

[JonMcCann13]

Yea welding would be great if I had a steel pan but I have the cast aluminum pan and no way to weld aluminum. I think I'm going to try tapping my hole where it looks like all the others I have seen is tapped and use a reducer to go from 3/4 to 3/8 npt pipe.

The inside diameter of 3/8 is pretty close to half inch so my thinking is it will be big enough to flow the oil out. Correct me if I'm wrong on that though

[mitch5]

Yea welding would be great if I had a steel pan but I have the cast aluminum pan and no way to weld aluminum. I think I'm going to try tapping my hole where it looks like all the others I have seen is tapped and use a reducer to go from 3/4 to 3/8 npt pipe.

The inside diameter of 3/8 is pretty close to half inch so my thinking is it will be big enough to flow the oil out. Correct me if I'm wrong on that though

Reducing the size of the hole is a bad idea, if you have improper flow will result in blowing your turbo seal. That's what happened to me, if you do all the work up to right before you weld you can get any fab shop to weld it for 20 bucks