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Oil Pick Up Thread Woes

#41

#41

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Changing the oil pan in the car (73 Charger 440), when I removed the pickup tube I noted that the end of the threaded hole in the block is quite rough. Some of the final threads are broken and uneven. After cleaning it out and checking the pickup tube threads, I am having a bear of a time getting it started. It's beating up the pickup threads and more fragments of threads in the block keep breaking off.

I am on the verge of getting royally ...... well, you know.... on this simple project!

Does anyone know where to get a thread chaser for the oil pickup hole in the block?
 
It's 3/8" pipe thread. Parts stores, hardware stores, borrow one?
Mike
 
You may need to grind the tap shorter to get it to clean up the outer threads if they are tapered.
If you need to do this you need to be very careful as these threads and the shortened tap make it very easy to cross thread.
You can linish down the first couple of threads on the pickup but you must be careful.
Do not take all the thread just the tops to make it easier to start.
 
Do you know history of the motor? PO may have opened pick up to 1/2". Very common upgrade on B motors. Just make sure of size before getting tap.
 
No such thing as a "simple" project.
I could share a story or two.
Replacing a dipstick tube with a chrome one in a 340 comes to mind. :rolleyes:
 
It maybe NPS thread. This was pointed out in another thread. I'd find out for sure.
 
Fran Blacker may be right when I did my 340 motor which is a different system I remember it was some oddball thread.
Unfortunately I cannot recall what it turned out to be.
 
factory threads for the oil pick up pipe is 3/8 pipe thread. if it is something else in your engine well, welcome to hotroding….If you don't know the difference get someone who does, you don't want to muck this up.
 
If can measure bottom of threads to see if all the same depth. If so it's probably NPS it's called National Pipe Straight. Easier to do on a good thread. Hope someone has a for sure answer.
 
Thanks for the replies.

I did read elsewhere that it is NPS 3/8 in stock form.

I took a break for awhile and hit it again: I tapered the last couple ratty hole threads in the block with a carbide bit. Then I took an old Miloden pickup, chopped off the end and welded it to a socket. I was then able to use a 1/2" long extension and applying pressure .... used the Miloden pickup end to cut through the ground area and chase the remaining threads.

I'm not pulling an engine tomorrow! Whew.
 
Unless it's been monkeyed with, it's 3/8" NPT (national pipe thread). The casting is thin enough where it
is such that when it's tapped at time of manufacture, it doesn't get the full taper that usually comes with
pipe threads - the hole is pretty much a "square shoulder" tap with no taper to it.

All that means is that it might be a tad of a bear to get a pick up started in it, but if you concentrate on
the actual end of the pick up tube and the threads in the block, NOT the casting shoulder, and mate
them up perfectly squarely with one another, it'll go.
Pick up tubes, unlike the threads in the block, actually do typically have the full taper of pipe threads on
them, meaning the thread diameter starts smaller and gets bigger as you go up.

It also means that if you want to run a thread chaser up it first, then as others have said, you'll have to
lop off/grind off some of the chaser so that the tap engages the threads in the block at its' biggest diameter
(which means the same as starting the pick up tube in it - HAS to be perfectly square to one another).
 
NPT - also used to indicate national pipe taper or tapered, to describe the thread form. There are specs for threading and tapping. As others have stated, if you run the tap in too far, you ruin the taper for the standard male thread. Back in the good ol' days, pipefitters used lampwick - pulling off a single strand, and wrapping it tightly in the root of the male thread, starting a half thread back, using pipe dope to hold it. It will partly be torn as is tightened, but the bits that remain can solve leaks on damaged threads.

Or you could try Expando...

https://www.xpando.com/xpando.php
 
How about a pic or two of the offending threads?
 
I presume it's a stock 3/8 NPT pickup. A 3/8 NPT tap for the block, & a 3/8 NPT die for the pickup will get you what need if the threads on either are not too badly damaged.
 
I didn't take any pics and its is now back together. It was the stock 3/8 size.

The Miloden pickup tube is made of a higher strength material than the stock pickup tube and I figured it might make for a good thread chaser if I could make sure it was straight by having a long extension on it and be able to apply some slow force. I got lucky on this one because those first few threads in the block were really bad.

I think I'll still find a thread chaser just to have it in the tool box in case this ever happens again.
 
you do not need a therad chaser
just a couple or pipe taps from harbor freight
you may have to cut one off s was said
just clean up- do not try and cut deeper until you do a test fit with your pipe
you can't put metal back :)
 
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