What size thread/fitting for 3B diesel oil port? (1 Viewer)

[robmobile73]

I put a turbo on my 3B. My oil supply line goes to the oil port on the engine below/behind the alternator. The thread on the plug did not match any threaded bolt I could find, but is very close to 1/8 NPT. I assumed it was a taper thread and 1/8 NPT will thread in and then you can force it a couple turns till i'ts tight. I'm still getting some leakage. It is annoying. What thread fitting do I need to use in these oil ports to get a no leak oil line????
Seems I"ve heard something about a AN/JIC fitting somewhere, but I"m not sure where.

 

[roalco]

It's been many years, and I may be wrong, but I think it's 1/8" BSP (British standard pipe thread), that's a parallel whitworth thread, 55 degrees, at 28 tpi, that needs an oring or crush seal, as opposed to 1/8" NPT (national pipe taper) a tapered 60 degree thread at 27 tpi.
So you're only getting a small area of thread contact and no sealing as from a male to female taper thread. You will get leaks. You need the correct fitting, or an appropriate adapter. Let's hope that you haven't damaged the thread in the casting!

 

[gerg]

I use bsp adaptors and never have leaks, but I do use teflon tape.

 

[robmobile73]

It's been many years, and I may be wrong, but I think it's 1/8" BSP (British standard pipe thread), that's a parallel whitworth thread, 55 degrees, at 28 tpi, that needs an oring or crush seal, as opposed to 1/8" NPT (national pipe taper) a tapered 60 degree thread at 27 tpi.
So you're only getting a small area of thread contact and no sealing as from a male to female taper thread. You will get leaks. You need the correct fitting, or an appropriate adapter. Let's hope that you haven't damaged the thread in the casting!

Thankyou, I will look for a BSP thread. This is something I have to order versus being able to buy off the shelf. Somewhere else I have seen something about JIC fitting, but cannot find it anymore.
The 1/8 inch npt screws in a little and then becomes difficult and subs stops. kind of like the thread is close but not quite exact. I assume this was due to a taper thread. The npt fitting is brass so I assumed it would deform to the threads in iron block if need be. I use some Teflon tape but it is still not quite good enough.

 

[jblueridge]

Mcmaster Carr sells BSP adapters and fittings.
I have read of people running a NPT tap into the BSP hole.
I just bought an adapter.

 

[Greg_B]

Yes, as mentioned above 1/8 BSP. This thread has some adapters discussed.

hth's
gb

 

[roalco]

Just FYI, the seal on a tapered pipe thread actually is designed to occur in the thread engagement, Teflon tape, properly applied, is only a lubricant to get full and proper engagement. That said, tapered pipe treads are only really effective when the threads are initially used, not re-used, as the thread tips are deformed during initial seating.
I know, too much information, just hand me more of the white sealant goop!

 

[robmobile73]

I'll try to see if I can o

Just FYI, the seal on a tapered pipe thread actually is designed to occur in the thread engagement, Teflon tape, properly applied, is only a lubricant to get full and proper engagement. That said, tapered pipe treads are only really effective when the threads are initially used, not re-used, as the thread tips are deformed during initial seating.
I know, too much information, just hand me more of the white sealant goop!

I will definitely use teflon tape. I really don't like old leaks just makes you feel insecure about your vehicle even if it's just a minor leak. Not to mention the spots on your concrete driveway.

 

[robmobile73]

Ordered 1/8 BSPT male to 3/8NPT female fitting today from macmaster car. I will go from that to 1/2 barb. Rubber line to the oil line fitting on the turbo.
Unfortunately my turbo gave out 2 nights ago. bearing/oil seal was weeping since new and it finally let go. It was a $99 turbo off of Ebay out of Hong Kong.....Some don't last and I got a bad one. Rebuild kit on the way and perhaps the seller will do something for me so I don't give them a bad review that their turbo went out at less than 1000 miles.