Tapping Into Oil Passages

I'm in the process of installing an oil cooler and have plenty of experience with a drill press and tapping machine threads, but no experience with oil lines and pipe thread. From pamcopete's photos and others it seems I'll need a couple of 3/8" inside diameter barbs with 3/8" NPT threads on the other end. Will I need a special tapered tap for NPT threads? I have plenty of regular and metric taps, but none tapered. If it does require a tapered tap, how many turns in do I go for the standard diameter?

Do you have any other suggestions for a sealing fitting..copper washers and a banjo bolt for instance.

Thanks.

NPT threads require a NPT tap. Bear in mind that your pipe taps don't correspond to OD, but more loosely to ID. A 1/4" NPT thread is more like 1/2" in diameter. NPT taps aren't expensive, and most hardware stores should have one. As for how deep to go, it is a little bit guess and check. Generally you run the tap in about as far as you want the fitting to go in, but the variance is wide. Tap it a little, thread your fitting in to check, tap it some more....

See above, you will need 1/8 or 1/4 NPT

pyrocentric,

Well, I used a 1/4-18 NPT tapered tap for the oil line fitting. Use a 7/16 drill bit to start.

Harbor Freight has a three piece set of NPT taps. I paid $14.95 for a set. Not great taps but for aluminum they work. 3/8, 1/2, 3/4. Are the sizes.
You can get just a 3/8 npt tap from some supply houses but you can spend $40 on just one tap.
That's how I threaded my side cover.
If you have seen the pics then you know which hole to tap and where to plug the passage.
Once you get the hole tapped you need a 90 degree elbow, then the 3/8's hose barb.
I don't think a banjo bolt would have enough flow. Fine up at the head where not much flow is needed. For an oil cooler you want plenty of flow. Stick with the 3/8 fittings.
I drilled out my fitting as much as I dared, I think I used a 5/16ths bit. I think the 3/8ths is the outside diameter of the barb. The inside is smaller. The elbow is smaller inside too.
I used JB Weld as a sealer. It seals and reinforces the joint.

put heavy grease on the tap when tapping the threads to catch as many of the chips as possible no sense in sending them thru the oil pump later

jayel,

I removed the cover when I tapped. Particles left here will go to the oil cooler and then the screen. This point is past the oil pump.

I try to never under estimate what people will do or are capable of doing

Yeah, the side cover is off and disassembled. That's what I needed to know guys, thanks.

Got everything assembled. I chiseled out the lead putty used to seal the two oil passages, then drilled into the steel plugs and tapped them for a 6mm bolt. I screwed in the bolt with a stack of washers to pull the plugs out. I plugged the original oil passage into the filter chamber with a piece of 3/8" steel rod, which fit pretty snug, and a tiny roll pin beat into a tiny hole I drilled from the side with a healthy coating of blue threadlocker. Per pete's excellent suggestion, I drilled through the plug and used a short roll pin so I can beat it into the plug and remove the plug later if needed.

The oil holes on the bottom were tapped with the 1/4 NPT tap. The bottom brass fitting is a 90 degree bend to a 3/8" inside diameter hose barb. I put a 90 degree female fitting in the next hole so that I could add a temporary oil pressure gauge or just plug it.

I decided to tap the return line into the side of the filter cover like I'd seen one on here. Very tricky. There is barely enough solid cast material to make the notch in the clutch cover without breaking though it, and only in the exact spot I put it. I used a rotary rasp and just gently pushed down to cut the notch, then cleaned up the rough edges with hand files. A 1/4 NPT fitting won't fit sideways in that filter cover, so I dropped down to 1/8 NPT fittings but drilled them out to make sure they had the same 3/8" inside diameter all the way through. There are empty chambers around the edge of the filter cover, where the gasket surface is, so I filled them with alumaloy(it's like an aluminum solder, you melt it with a propane torch) so that when I drilled a hole it would be in solid aluminum all the way through. I didn't put any of the NPT fittings in very deep, 4 turns deep I think. Didn't want to take the risk of cracking the clutch cover. I did use a small amount of permatex thread sealer, which I'm pretty sure I can remove later if needed. Just used a bit of teflon tape on the oil pressure gauge. No leaks.

I used an old VW oil cooler I had sitting around. Tapped two more NPT fittings into it(upside down, slathered in grease and pushing air pressure in from the other hole to keep the metal filings out of it.)

Motor built up oil pressure right away and got to the top end(I pulled off a valve cover to check). I'm running 20W-50 oil. At cold idle I had 16psi. Rev it cold and it goes up to 40psi or greater. Once it warmed up I had 1psi at idle. That's right, 1psi, maybe 2, hard to tell. Rev it and it went up to 20 or 30psi again.

After a short ride around surface streets on an 80F day my oil temp was 150F. At the spark plugs I am reading 290F and 300F, left and right. I saw 330F at the plugs last summer. Jugs are at mid 200'sF. So far it seems that my oil is actually too cold and my head is still too hot.

Will probably try ducting some more air to the head and jugs next, much like a VW does. Would also like to come up with some sort of fan system for these interminable stop lights I can't avoid here in the city, but that may be too much work. Open to suggestions, but thanks for all the advice so far.

Now that I think about it those pressure readings seem way too high. If that kind of pressure is getting to the filter it's certainly pushing the bypass valve open. Maybe my cooler is clogged or too restrictive. I'll bypass it when I get home tonight and take some more pressure readings.

pyro...,

Yes, those pressure readings are too high. Should be about 4 to 7 PSI at 3,000 RPM after the engine is warm and, yes, it does go to zero at idle.

But, the point where you have the pressure gage installed is the inlet to the cooler, so if the cooler is plugged, that would explain the high pressure. I installed my pressure gage on the cover of the oil screen which is the outlet of the cooler.



I had this same arrangement on my '78/E for 12 years and even though I would sometimes put my foot on the fittings, they held.

I removed the oil cooler and ran straight hose from the inlet to the filter chamber. Cold idle is 10psi at 1200rpm and goes up to 30psi and climbing at 3000rpm. I then removed the filter housing and ran it for 10 seconds to watch the oil pour out...good flow, plenty of oil, not exactly spraying out just a solid pour. Filter is clean and I can move the bypass spring with gentle pressure.

The cooler adds some resistance, so I guess my oil pressure readings and yours will differ due to where I mounted my gauge. I think I remember reading that the bypass kicks in at around 14psi, so if I let it idle and warm up before revving it I might be fine.

I still don't like seeing the pressure shoot way up past 30psi, but the hole that feeds the engine is very small compared to these oil lines. I even took time to center the filter so that the filter outlet hole lines up right.

pyro,

The pressure will go up past 25 with a cold engine, but if you are seeing 30+ PSI with a warm engine, something is wrong.

Measuring the pressure at the oil screen is important because that is the pressure going into the engine. I suggest that you measure it there by tapping into the cover. You can always get a new cover after you finish with this setup. Just use a plug while waiting for the replacement cover from EBay.

Pyro, the way you have the gauge plumbed in, you are reading the pressure before the coller.
The way Pete has his plumbed is after the cooler.
I might replace the elbow on your return line with a tee and hook the gauge there. This will be just before the oil goes to the filter.
I used a cooler off a Seca 650 turbo. You might want to try a different cooler.
Leo