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On one the first starts on my 73 restoration project, I notice I didn't have any oil pressure showing on the gauge. I was pretty sure I had oil pressure because the engine wasn't making a lot of noise but shut it down just to be on the safe side. Using the forum, I was able to find out how to check to determine whether it was the gauge or the sending unit. Turns out it was the sending unit. I ordered a new one from Zcar Depot. I installed it and that took care of the issue. I started noticing a small oil leak under the car. I had a hard time locating the source but finally discovered it was coming from the oil pressure sending unit. It appeared dry around threads, but i removed it and sealed around the threads with permatex and reinstalled, still leaked, still dry around the threads, tried again using teflon tape, seemed to get worse but still dry around the threads. So i removed it again and figured it may be leaking around the back seam where the front and back portions of the unit come together. I did notice some oil there. On the bench, I injected some air into the unit and quite a bit of oil came out around the seam. I notified the guys at Zcar Depot and they were very accommodating (as usual) and sent me out a replacement. The first one they sent me was silver and screwed into the block very easily. I was able to get 3 or 4 turns on it before having to use a wrench. The second one was a Beck/Arnley brand and gold in color. I had a hard time getting it started in to the block and when I did I could only get about 1/2 turn on it and it was very tight. Here's what I did. The threads appeared to be 1/8"-27 NPT thread. I ran a tap in the hole in the block. It threaded in smoothly without the use of any tools. Then I ran a die of the same size on the threaded side of the sending unit. It took a little more effort but nothing excessive. I then buffed the threads on a wire wheel to remove any of the gold plated coating. I was now able to start it into the block hole about one turn or so. Using a wrench I would turn it one turn at a time then back it out, it was still pretty snug but seemed to be going in smooth and straight. I did this 4 or 5 times, turning it in a little deeper each time until it felt like it bottomed out (or was in as far as it would go). That took care of the problem andi the leak. I thought this info may be helpful in case others run into the same issues. The attached pic shows where the oil was leaking out once I applied air pressure to it.