Does anyone know off hand what size threads the oil pick up tube for a truck style is? I bought the melling 66S5 for my 76 truck motor (going in my 86) and the dang thing ripped the threads right off it before i could get it where i wanted it. Now I'm back to reusing my stock one but its not resting on the pan due to thread stretch (sits about 1/4" away from the bottom). I was hoping to get a die nut to "recondition them" to get it to bite a little sooner or try to use some thread locker i guess to lock it where i want. It looks like straight 3/8" tapered pipe thread but not sure. The block side threads are fine.

You claim " thread stretch" I can't see any kind of "stretch" making something too short.

I believe its to short because it has to be screwed in farther to tighten cause of the thread stretch. This is what it looks like, i was trying to find a die nut to try to salvage it. Just not sure of the size pipe thread, was hoping someone knew for certain.

You are on the right track, the pick up screen head should interfere with the bottom of the pan. Since the tube is going in too far here are a couple of options:
1) weld a couple of spacers of the appropriate thickness to the bottom of the screen head to make up the distance. A couple of light tack welds would be plenty to hold a spacer. Adding spacers to the bottom of the screen head to get it off the pan floor while maintaining contact for support is a racers trick used to assure good oil flow to the oil pick up head.
2) use a Loctite product to set the oil pick up tube position, with out the tube threads being mechanically tight. The typical Loctite that you find at a big box car parts store is not what you want to use. You would want a Loctite product made for that purpose. Call the Loctite tech line and tell them the issue, they will have some thing that would work. Then shop e bay or on line to find it.
3) if finding the absolutely correct product to lock the NPT threads is not your cup of tea, put JB Weld or any other temperature resistant epoxy on the threads. Be sure with either 2 or 3 both sets of threads are absolutely clean and dry.
I am suggesting these fixes because I don’t know how one would re cut tapered threads with out making the taper less of a taper.

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If you are going with the welded on spacer route, an easy way to get the thickness required is to set the oil pick up where you want it, with the crankcase upside down, put a couple of pieces of modeling clay on the pick up and set the pan in place. Remove the pan and measure the thickness of the compressed modeling clay. That will give you the thickness of the spacer.
When doing this be sure to have the crankshaft in place and rotate it to verify there is no interference.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

The truck tube is long and that is a lot of weight out on the end. The threads can weaken and break. So for sure get it touching the bottom or add a brace to it which is what i did to my last two truck pick ups.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Thanks everyone, ya the more i think about it the more i don't think running a die nut on the threads is going to fix it. I like the welding the spacers onto the screen end idea (didn't think of that). I might go with combining that with the molding clay to figure out the total depth I need then cut a section out of the botched melling pick up and weld it to the oem pickup to extend it to where i need it (touching the bottom of the pan) and finding some high temp Loctite to use on the end so it doesn't come loose.

Be careful welding in a section in the tube to make it longer.
The weld will need to be air tight or it will loose some suction and also free of weld debris on the inside or it will add contamination to the oil stream into the oil pump.
It may be simpler to add spacers (washers) to the bottom side.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

An idea I had while following this thread would be to use an appropriately sized nipple screwed into the block with a treaded coupling on the end of the shortened and rethreaded pickup tube. Doing this would create a secure connection to the block and allow for adjusting the overall depth of the tube for proper placement in the pan.

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1975 Dodge D100 225 c.i., HEI, Parallel Offenhauser, Motorcraft 2150, 904 auto, 9.25" 3.55:1

Yep, good thought. I have done exactly that (NPT nipple+union) a few times, but mostly when I am deepening the pan and extending the pickup.

Lou

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That is a great idea too i might have to steal that haha, something like this