Need help fast! Oil pressure gauge install trouble

mdost03 · 05-29-2008

OK, I am very confused by this car. I'll tell it slowly so everyone can understand.

I know our cars use a 1/8" BPT thread pattern on the oil pressure sending unit. I bought an Autometer Ultra-Lite gauge from Summit and I am trying to install it. The sender has a 1/8" NPT thread type so I bought a 1/8" NPT to 1/8" BPT adaptor from them (Autometer) to use to install the sender. I removed the stock sender with no problem and I go to install the 1/8" NPT to BPT adaptor and it won't screw in. Will just barely start and then stop like it is cross-threading almost. Tried screwing in just the 1/8" NPT sender from the gauge and it does the same exact thing. Tried screwing the stock sender and it screws in just fine. Checked the package and I have the right adaptor. Weird thing is, the stock sender with the 1/8" BPT threads screws into the 1/8" NPT adaptor side with no problem, screws in about as far as the aftermarket gauge sender with the 1/8" NPT threads.

Now here is my question, should I try forcing the BPT adaptor on (don't feel comfortable doing this) or should I use this 1/8" NPT tap I have here and thread it into the oil pressure sender hole? The tap goes in about 3-4 full turns before stopping. I've read on tuners when I did a search that people have tapped the BPT thread pattern with an NPT thread pattern no problem, but wanted to see what everyone's opinion or experience on this matter is. Thanks and quick replies are appreciated since I was planning on installing this gauge today and get it out of the way so I can put the engine back together this weekend.

**asshanson** · 05-29-2008

I thought the stock sending unit had 1/8" NPT threads. My prosport one with 1/8" NPT threads went right in with no problems.

mdost03 · 05-29-2008

Everywhere I've read, our oil filter housing's use 1/8" BPS/BPT threads

**asshanson** · 05-29-2008

Well you said yourself that the stock and aftermarket gauges both screwed into the NPT adapter the same. Anyway, I have a different oil filter housing, so the threads could be different.

I just did some reading on British pipe thread, seems it's very close to NPT, one thread per inch less for 1/8" size. Retapping sounds pretty safe.

DSM_421 · 05-29-2008

Mike, your cover *should* be there by saturday.

mdost03 · 05-29-2008

Sounds good DSM_421, car won't be going until about mon-tues hopefully, so no rush.

Well I ended up just taking a 1/8" NPT tap to the hole and threaded the oil pressure sender directly in there with no adaptors. Hopefully it won't leak, but I think it should be ok. Will find out next mon-tues if it needs to be tightened up more or not.

AwdGSX13 · 05-29-2008

if its nice and tight and it wasn't forced, i dont think you should have any problems.

Kevin 1G Drummer · 05-29-2008

When I installed my Prosport gauge I just put the sending unit right in the stock hole. Like you said, it would go in a little, then stop. I ended up using a wrench on it, but I was by no means forcing it. It went right in, and doesn't leak. Just to be sure, I used some teflon tape.

mdost03 · 05-29-2008

I used some teflon paste around my sender. I didn't have to force it on after tapping so I think I'm good. Was really weird though why the adaptor or the sender wouldn't screw into the stock threads.

Doesn't have to be super tight in there does it? Mine is pretty tight, but I could have kept going, but it's aluminum isn't it so you don't want to go TOO far in or wrench on it that hard?

**Kracka** · 05-29-2008

Keep in mind that NPT/BPT threads are tapered so its not supposed to thread all the way in like a regular bolt. As long as you used some Teflon tape (or other pipe sealant) and got a 4-5 threads in it'll be perfect and sounds about right.

mdost03 · 05-29-2008

Quote:

Originally Posted by Kracka

Keep in mind that NPT/BPT threads are tapered so its not supposed to thread all the way in like a regular bolt. As long as you used some Teflon tape (or other pipe sealant) and got a 4-5 threads in it'll be perfect and sounds about right.

Cool, thanks for all the help guys, got the gauge mounted and wired up and looks great! I'll snap a picture here quick and post it.

mdost03 · 05-29-2008

Sender on oil filter housing:

Pictures of the gauge mounted:

**Kracka** · 05-29-2008

Get that thing on the pillar with the boost gauge!

xveganxcowboyx · 05-29-2008

Or at least switch it with the boost gauge. Oil pressure shouldn't look like the most important gauge in your car.

mdost03 · 05-29-2008

I put it there because the oil pressure gauge behind it didn't work. I am used to looking on the pillar for the boost gauge from my old car so that is why they are the way they are. I kinda like the single gauge on the a-pillar. Doesn't look so cluttered.