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Oil Pressure Sender

Posted: 27 Dec 2014 16:39
by TheHeretic
In going through the L20b I picked up a few months ago, I'm cleaning and upgrading some of the parts for reliability. I've already put on the higher volume KA24E oil pump and will be doing the internally regulated alternator soon. The engine already came with the following fitting and line (see pics below) for an aftermarket oil pressure gauge but it's leaking and look pretty sorry. I would love to get some suggestions for updating it to not only not leak but also improve the reliability of the entire unit. Basically what would you do?

Any help is much appreciated!

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Re: Oil Pressure Sender

Posted: 27 Dec 2014 17:55
by okayfine
The threads are stripped? No good seal, there. Do you know where it was leaking, relative to that adapter and set of fittings?

Also, is that AN adapter 1/8 BSPT. The block is, but most likely it's 1/8 NPT. Close, but no cigar.

Re: Oil Pressure Sender

Posted: 27 Dec 2014 19:31
by bertvorgon
This is what I did for my engine. Block tapped out for new steel fitting, then, ran the Aeroquip line over to a "distributor" block mounted on the inner fender base.

This takes away any vibration issues, then, you can run both an oil pressure gauge, low oil pressure Hobbs switch ( which I have set at 45 - 50 PSI, then hooked to large light on dash ), and, if applicable, a turbo feed line.

those brass fittings are the worst thing we can use, as they tend to fracture with fatigue over time.

Maybe this will help or give you some ideas.

Re: Oil Pressure Sender

Posted: 27 Dec 2014 19:43
by bertvorgon
The large red light on the dash is the low oil pressure warning light. I can guarantee you that you will never see a gauge under combat conditions, if things go south in the motor, in time, whereas when this light comes on at 50 PSI...you will not miss that. With a Hobbs switch, you can crank the pressure down for traffic use, if you find it too annoying in everyday use.

Re: Oil Pressure Sender

Posted: 28 Dec 2014 09:59
by okayfine
Nissport makes/made a steel oil pressure distribution fitting. Correct BSPT male thread, three NPT female threads for Autometer (et. al) gauge senders.

DQ Volume 6 Issue 1 - Product Review: NISsport Oil Pressure Adapter

Re: Oil Pressure Sender

Posted: 28 Dec 2014 22:00
by TheHeretic
Naive question - how call I tell if its BSPT or if it's been tapped so that it is now NPT? I think it would be BSPT..why else would there need to be an adapter, right?

Re: Oil Pressure Sender

Posted: 29 Dec 2014 09:06
by okayfine
They're very similar. NPT will thread in to BSPT about one full turn by hand, and can be made to thread in more than a few with a wrench, but by then you're gacking the threads on one or both parts. That alone may have been done to your port already. Since NPT will thread in, people hooking up oil pressure gauges with NPT just assume it's a tight fit and start cranking on the wrench - been done a thousand times.

If you have a new threaded piece of one or the other you could give it a shot and see what happens, or compare threads with the used parts you have.

Also not sure where your adapter fits in to the pieces in your third picture - in your third picture there's already a brass adapter in the end of the AN fitting. If you have the adapter in Picture 1 threaded into the block, then the adapter in the hose is threaded onto the adapter in the block, AND those threads are already fully gacked...then, yeah, that's going to be a source of oil leaks at 60psi.

Re: Oil Pressure Sender

Posted: 29 Dec 2014 19:46
by zKars
This may help the cause a bit. Autometer makes a nifty little 1/8" BSPT to NPT adapter. Its part number is 2269.

http://www.summitracing.com/dom/search? ... ter%20bspt

I found them instock at the local speed shop (Mopac). Shouldn't be too hard to find for anyone in a major center. McMaster Carr has several BSPT to NPT fittings as well for you US based folks.

Re: Oil Pressure Sender

Posted: 30 Dec 2014 00:47
by Byron510
Just go be a little more clear as to why the 1/8" BSPT and the 1/8" NPT are almost the same - but not quite.
The thread pitch of the 1/8" BSPT used in our Nissan parts is 28 tpi (threads per inch), uses a 55 degree Whitworth (rounded) thread form.

Where the North American standard 1/8 " NPT is 27 tpi, utilizes a 60 degree sharp V thread form.

Both taper at 1 in 16 or 3/4" to the foot.

Very close at a glance, and as Julian pointed out it will start in the hole, but they are not the same and do not interchange with each other now that you see the information above.

It's like threading a 5/16UNC nut on an M8X1.25 stud. The nut will start by hand for about 3/4 of a turn. And a wrench will force the nut down the stud with moderate force. Only you’re adding an inclination of a tapered thread profile into the picture. But ultimately you destroy both parts and significantly weaken the fixation of the two pieces as a result of improper engagement.

Byron

Re: Oil Pressure Sender

Posted: 02 Jan 2015 17:43
by TheHeretic
Thanks for all the assistance so far! I have not have a chance to get around to purchasing the adapter yet and might just wait until I drop the engine/tranny in over the next couple of weeks and then get around to fixing these little issues. It was only leaking a little so for now I will probably just put some non-hardening sealer on it (Permatex #2) to hold me over for a while. I'll keep the forum posted on how I decide to fix it. Not sure how much I care about the oil pressure light working if I have a gauge though.

Re: Oil Pressure Sender

Posted: 26 Mar 2015 13:51
by BlackWidow
bertvorgon wrote:This is what I did for my engine. Block tapped out for new steel fitting, then, ran the Aeroquip line over to a "distributor" block mounted on the inner fender base.

This takes away any vibration issues, then, you can run both an oil pressure gauge, low oil pressure Hobbs switch ( which I have set at 45 - 50 PSI, then hooked to large light on dash ), and, if applicable, a turbo feed line.

those brass fittings are the worst thing we can use, as they tend to fracture with fatigue over time.

Maybe this will help or give you some ideas.

Did you tap this hole for a larger fitting? I am curious what size AN fitting is coming off that.

Re: Oil Pressure Sender

Posted: 28 Mar 2015 15:42
by bertvorgon
Just saw this post, yes, we did tap out the block when I built the engine. I'm not sure which dash size
that is..my engine builder did that, and I don't want to guess on you.