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MG MGB Technical - Oil filter thread size

I ran into a problem changing my oil today ('74 B, inverted spin on filter). the old filer, an K&N HP2004 came off no problem. When I went to put the new filter on, it tightened up after a few turns, long before the gasket touched the filter head. I took it back off and I can see that it had damaged the threads slightly. I tried to put the old filter back on and got the same results.

Before I do anything else, I want to try to restore the thread on the post of the filter head.

What is the thread size on that post (spindle)?

Dan
Dan Hiltz

Dan - I don't know the thread size right off hand (I'm sure someone will come up with it shortly), but are you sure that you got the filters started straight? It is real easy to get them started slightly off and have the threads jam. Cheers - Dave
David DuBois

Thanks Dave. I think I started it straight. I always turn it counter clockwise until I hear and feel the filter threads drop into place on the spindle. It's always worked before but I can't imagine any other cause for this happening. I can't belive that the threads on the new filter are defective.
Dan Hiltz

Dan,

I don't know the thread either, but it was discussed extensively a month or so ago. So you might try searching the archive.

Also, since those are pretty course threads, you could probably remove it and dress them up with some tiny files like you can get at a hobby shop or tool supply.

Was the new filter the same make and number?

Charley
C R Huff

Thanks Charley. Yes, the new filter is the same make and model. If no one answers here, I'll call K&N on MOnday and see if they can tell me.

I searched the archive but didn't have any luck. I'll keep trying.
Dan Hiltz

Dan-
3/4" x 16 threads per inch.
Stephen Strange

Thanks Stephen. I really appreciate your help. Is that SAE, BSP, or does it make a difference?

Dan
Dan Hiltz

Dan-
It's SAE.
Stephen Strange

Dan,

It is possible that I saw the filter discussion on the Spridget side since I have both cars and watch posts on both. But, I thought the oil filter issue was on the B side. Hope I didn't send you on a wild goose chase.

Anyway, it looks like you got your answer on the thread pitch.

Charley
C R Huff

Starting it right is tricky as the threaded spigot is at a slight angle. In the very early days I cross-threaded mine too, and found several shards of metal lying at the bottom afterwards.
Paul Hunt 2010

Thanks guys. The damage seems to be limited to on e small section and doesn't go all the way around. I ordered a thread file yesterday so I'll try to repair it with that. I'll post the results.

Wish me luck! Thanks again.
Dan Hiltz

It's aluminum, so be gentle. I purchased a used spin on adapter in a wrecking yard some years ago and it still had the filter installed. The mechanic refused to remove it. When I got home I found out why: the first 3 threads were stripped off completely. After using it for a month, I ordered a new one. I had too much money invested in my engine to trust what was left of those threads. Hope you have better luck. RAY
rjm RAY

Dan-
Here's an old Tool & Diemaker's tip: Be very conservative with that thread file. Once you remove the metal, you can't put it back on. After you finish with the file, run a sizing die over the threads to form them up properly.
Stephen Strange

Lots of good input. Is it generally better to skip the file altogether and rely on the die? Thanks.
Dan Hiltz

And is the thread alloy? It's always looked and felt steel to me.
Paul Hunt 2010

Good Question Paul! I'll check it with a magnet.
Dan Hiltz

Looks like the spindle is ferrous but not the threads.
Dan Hiltz

Interesting.
Paul Hunt 2010

That's why I'm always extra careful when installing a new filter. It's very easy to crossthread the stanchon pipe threads. RAY
rjm RAY

Progress report. I tried to clean up the threads with the file but had no luck. Had to resort to the thread chaser and it cut a new thread in the aluminum spindle. But afterwards the filter went on very easily. Won't be able to run up the engine until tomorrow so I can't be sure it's properly seated, but a visual insoection with a mirror is encouraging. It looks like the gasket is snug all around. Thanks for all the pointers.

With me luck!
Dan Hiltz

This thread was discussed between 13/03/2010 and 02/05/2010

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.