Tapping block for return line?

[keada714]

Hey guys,

I know most, if not all are tapping their oil pans for the return line. However, any ill effect of tapping the block instead?

[Northern]

Done it on my iX, on the flat spot under where the A/C bracket goes.

I drilled and tapped a hole to accept a -10 AN union.

At the white X:


Obviously there's the risk of swarf getting in the oil if done in situ, but you can attempt to flush it out, or drop the pan.

Pros of tapping the block would be:
Shorter, more direct return line.
No additional bits to un-do when dropping the oilpan.
Steel/thicker material allows you to tap and install without welding-on or using a bulkhead fitting.

[keada714]

Will probably go this route with the m52. Thanks

[cek]

Done it on my iX, on the flat spot under where the A/C bracket goes.

I drilled and tapped a hole to accept a -10 AN union.

At the white X:


Obviously there's the risk of swarf getting in the oil if done in situ, but you can attempt to flush it out, or drop the pan.

Pros of tapping the block would be:
Shorter, more direct return line.
No additional bits to un-do when dropping the oilpan.
Steel/thicker material allows you to tap and install without welding-on or using a bulkhead fitting.

Won't this interfere with the AC compressor?

Do you have any pics/guidance on how you actually drilled/tapped this (I've never done a fresh tap before).

[Northern]

Won't this interfere with the AC compressor?

Not if you delete your AC :p

Do you have any pics/guidance on how you actually drilled/tapped this (I've never done a fresh tap before).

Mark the hole on a nice flat spot, make sure there's no reinforcement inside the block:


Grab some lube, drill and tap the hole to 7/8-14 to accept the -10 fitting. If you could mount a drill guide or use a drill press somehow it would go a long way, but a shitty cordless drill and eye of man were my tools of choice(or desperation):


I cut down the backside of a steel -10AN union so it didn't protrude into the block, chamfered the inner radius to smooth the transition of the dump into the block. Installed with loctite and capped it:

That's how I did my M52, and it leaked past the threads - the loctite didn't seal it, so I threw a fillet of RTV around the nut and that seems to have fixed it.


IF I were to do it again with the block out of the car, I would try to braze the steel AN union to the block, so I could hulk out and tighten the drain down without having to have a second wrench holding the union.

If you do have to do this with the engine in-situ, make sure you grease your bit to catch the swarf, and clean everything frequently while drilling, then flush the oil afterward a few times. No guarantee that you won't have some bits left in your pan though.

[jph]

I literally just got finished tapping my M52 block for a return. I used a 1/2 NPT tap and a 23/32 drill bit to make the hole. Got a 1/2 NPT to 10 AN 45* fitting and here is the result. Fits nice and snug but I'll probably put some thread sealant paste on it just to make sure.




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