Thread size for oil filler neck hose

[Postalpal]

I have a set of aftermarket valve covers that are similar in style to the Explorer type
The raised filler tube has a treaded hole
I'm trying to get the correct size barbed fitting to screw in to finish hooking up

Seems like a 3/8 fine bolt will screw in
But when I go to the hardware store all their barbed fittings are pipe thread. I picked on up that was the closest in size to my standard bolt but it will not go in. Surely they make a fitting that will just screw in here without me am having to tap it bigger


Any suggestions help thank you

 

[badandy73]

If it's 96-01 exploder it may be metric... 10mm?

 

[ntsqd]

Who made the covers? Their page may say what those threads are. Most likely they are NPT and if a 3/8" bolt nearly screws in then I'll guess that it is 1/4" NPT.

 

[Postalpal]

Still looking. Picked this one up at the hardware store and is too big

 

[ntsqd]

Any chance of contacting the mfg of the cover?

 

[Broncobowsher]

You are assuming that a mystery valve cover will be known to us. Can't tell what it is, who made it, where you got it, or anything else. A little picture of a screen shot of a picture doesn't help at all. There is no way for us to tell you what you are working with from what has been provided.

There is a chance it is one of the common NPT sizes, a better chance it is something completely different. If I was after a quick fix, drill and tap the hole into something known. Otherwise it is start measuring, get some thread pitch gauges and compare. Really good chance that the threads are metric. There is no law that says aftermarket stuff has to be built to NPT thread sizes.

 

[Wild horse 75]

With the recess around the opening I’m thinking it uses an o-ring to seal. So it really could be any thread metric or standard then have an o-ring against the hex flats on the fitting.

 

[ntsqd]

Not disagreeing with the o-ring guess, but if it is for an o-ring that is a piss-poor design for a std o-ring. A Stat-O-Seal would work better there, or a crush washer - but the thread depth is too shallow for much install torque.

I'm not usually a fan of NPT, but I'd run an appropriately sized NPT tap into that hole, install the desired fitting, and move on.

 

[DirtDonk]

And if that braided hose is permanently mounted, it looks like the vent hole is in a bad position anyway. You may be better off removing the valve cover and re-drilling the hole at a angle, more appropriate to your installation.

 

[Broncobowsher]

That could be an O-ring, maybe a crush washer? There was probably a fitting included with the valve covers that fit that.
NPT is a horrible design for, but somehow it survives and is still used. In America, probably the most used and universal threaded plumbing connection there is. Why you find it in every parts store around. You can make anything work with anything. Being there is no pressure involved, drill and tap is still my answer.

 

[ntsqd]

The chart here: https://cdn.midlandindustries.com/public/pdf/H_SAE.pdf lists the thread sizes of O-Ring Boss fittings, which just happen to be the same as the threads on AN/JIC 37° fittings. Notice that 3/8 UNF threads are the size used on -3 AN/JIC fittings. Those are pretty small for a crank-case breather fitting.
With the correct size of o-ring you can use an AN/JIC fitting in an ORB (O-Ring Boss) port. Note the angled pocket in the chart's drawing that the o-ring fits down partly into. That is why I say that port on that part is a piss-poor design. It's clear to me that the designer really didn't know what he or she was doing.

 

[Postalpal]

Any chance of contacting the mfg of the cover?

I'm gonna see if I can find where I bought them tomorrow
Thaxs

 

[Postalpal]

Done , 3/8 - 24. For the win
Now low lower the coil bracket a inch uggg

 

[Postalpal]

This one fit mine

 

[DirtDonk]

Thanks for the follow up.