I've always used the copper 1/8" line for my oil pressure gauges and never had an issue until this weekend when the copper line cracked and started to leak. Luckily my dad caught it early and was a simple fix, but it could have gotten ugly. I'm going to change to the stainless steel hose but should -3 AN or -4 AN be used? Is there any special fittings that will be needed when I change over?

-3 for sure.

Now you know why copper should not be on a car, especially a race car. I don't care that it(the gauge) came with copper, now you know why.

You'll need the appropriate AN fittings, IE #3 AN with either 1/16 or 1/8 NPT for the block and a similar fitting for the back of the gauge I like and use TFE type(teflon lined) AN hose for all my oil sytems, it will take a lot of pressure and live forever On the AN size #3 or # 4 will work, buy which ever one you can get all the fittings you need the easest (SP?) BTW, do you want to buy a premade hose or do you want to make yourself a custom made cut to length hose for your car I make my own, sometimes that can be challenging the first couple of times you make them, you will need a good cut off wheel for a dremel tool if you make your own

Never seen or heard of 1/16" pipe thread, they don't use them around cars and race cars.

Maybe less emotions? Be sure before you post Cab IMO.

The only fitting for the back of the gauge that I know of is -4. Jegs has it.

There are 1/16" NPT fittings.
http://www.summitracing.com/parts/fra-481602-bl/overview/

Most gauges I have seen are 1/8" male pipe thread and you use a 1/8NPT X #3 male AN adaptor along with a coupler or female 1/8" NPT AN adaptor.


Every line built, pressure tested and tagged by me. I built the entire car everything, except the chassis and body was built by Mike Bowen In Montrose Mi, near Flint.
3 AN lines.

I'll bet you that is a error, that listing.

Must be.
http://www.summitracing.com/search/department/fittings-hoses/section/fittings-plugs/part-type/an-to-npt-fittings/npt-size/1-16-in?N=4294951003%2B4294951002%2B4294948844%2B4294920995&SortBy=Default&SortOrder=Ascending

https://www.google.com/#q=1%2F16%22+npt+fittings

OK, for some reason they won't highlight as links, but copy and paste those 2 links.

Yes they make 1/16 pipe fittings... I have a 1/16 pipe plug on
my heads to block off the oil to the heads

You can use either #3 or #4 lines. I usually use #3 lines for the oil pressure gauge unless it is a super long run and then I'd use #4. You need the proper adapters for the gauge as well as the engine block. I use a bulkhead fitting for going thru the firewall rather than drilling a big hole and pushing the line thru.

#4 is huge for a oil pressure gauge and will just make your car weigh more and be more bulky around the gauges and motor, plus the fittings cost more. If he was using 1/8 OD line now that #3 is like 3 time as large which is plenty even on a super super long run. IMO Bulk head fittings just add to the cost, weight and more places to leak/come loose.

#4 is big... your only playing with the air pressure
thats in the line to work the gauge

I discovered you must type "link" or anything in the second box that pops up to make it a live link with blue letters.

I did find 1/16" pipe taps, so I was wrong, they make 1/16" pipe fittings. But I have never seen them used around cars, it would be a weak fitting that could crack too easy IMO. And what would you use it for around cars that small?, even mechanical fuel injection uses 1/8" fittings.

Some el cheapo gauges like this Sun gauge I have, can't be used with braided line because it is setup for compression fittings only. If this is the case you need a new gauge.


That is not 1/8" pipe thread, it's not even pipe thread.

On a better quality gauge you remove this which is 1/8" pipe thread and install a AN adapter.


These are fuel pressure gauges I had mounted to my street car on my hood. I used steel brake line to go through the hood vents not to damage my hood.
And then to brass inverted flare fittings to female 1/8" pipe thread and then 1/8" male pipe to #3 male flare to accept flexible stainless braided line under the hood.

The adapters from steel brake line to brass female 1/8"pipe and then 1/8" male pipe to AN #3 male flare adapter. 2 "adapters" used in the picture below.


These were mounted on my black 74 challenger for 20 years until I took them off so the cops looked at me less.

My point is I have been plumbing cars for 30 years and some serious race cars too and I have worked at a gas business since 1983 and I order fittings all the time and have several gas line technicians who work for me.

Can't get braided line down through my slots on my challenger hoods, But I could un flared steel brake line.

try this Autometer make them as a kit

http://www.autometer.com/accessories/adapters-fitting-hose.html


Tex

I used a 1/4 inch copper oil pressure line on one of my old race cars years ago, the oil pressure gauge reacted much quicker and faster than the other cars with 1/8 copper oil pressure lines NHRA ended up outlawing 1/4 inch copper oil pressure and fuel pressure lines several years later, maybe I should switch my cars to # 3 AN pressure lines now

mine came with a nylon line,been on there for 10 years and many thousand miles.mabey I should think of upgrading.

I have used small copper line and that plastic lines on street cars over the years before I went racing.

One time I was doing some soldering under my dash and by accident I melted a hole on my plastic oil pressure line and didn't know it until the next time I started the car. Then I had oil dripping on my feet, then I went to the small copper line which lasted for years on the street.

For a race car braided line should be used IMO.

Now what do you guys do when the line break and dump oil on the track? There is an old trick to get a brass 1/8" npt fitting and solder it closed then drill a # 60 drillbit hole in it. When bled it will allow oil pressure to pass but it wont empty your pan in 3 seconds.

https://www.vansaircraft.com/cgi-bin/sto...;product=va-128

This is one example.