I dont think its AN, but if you try it will fit and leak. its JIC. AN came out after the oil tanks were in production for many years. I know a lot of people will argue this because you can thread AN to it so take from it what you will. as for the size I forget, but wiki has a guide

edit.
oh wait, thats the side for the lines. motor and oil tank should be 3/8 npt

 

OK,
He's right they are'nt AN (at least I think) But 3/8NPT is HUGE. I know the lines are 5/16 steel. that should get you in the right direction. If my Pan was'nt up in the shed waitin for spring I'd go look.

Eventually someone might come along and tell the three of us off....

 

for some reason I had 3/8" in my head, NPT is right though? I have a pan tank in the shed I'll check tomorrow.

 

Good nerd AN vs. JIC reading. Both share the same 37 deg flare and I have used them together without leakage. The AN uses the stronger J class thread making it 40%stronger. They both use a dash number to tell you what tube OD they correspond to -2, -4, -6 and so on. Although I know we are now talking about an NPT.

http://weislake.com/sig/mucker/an-vs-jic.pdf

<TABLE border=0 cellSpacing=0 borderColor=#ffffff width=900>[TR]<TD height=30 borderColorLight=#ffffff borderColor=#ffffff width="100%" borderColorDark=#ffffff align=middle>[/TD][/TR]

[TR][TD]AN (Army-Navy) Fitting Thread Size Chart

<TABLE border=1 cellSpacing=0 borderColor=#000000 width=400 bgColor=#ffff00>[TR][TD]

AN Size

​

[/TD][TD]

Hose Size

​

[/TD][TD]

Thread Size

​

[/TD][/TR][TR][TD]-3[/TD][TD]3/16[/TD][TD]3/8-24 SAE[/TD][/TR][TR][TD]-4[/TD][TD]1/4[/TD][TD]7/16-20 SAE[/TD][/TR][TR][TD]-6[/TD][TD]3/8[/TD][TD]9/16-18 SAE[/TD][/TR][TR][TD]-8[/TD][TD]1/2[/TD][TD]3/4-16 SAE[/TD][/TR][TR][TD]-10[/TD][TD]5/8[/TD][TD]7/8-14 SAE[/TD][/TR][TR][TD]-12[/TD][TD]3/4[/TD][TD]1-1/16 SAE[/TD][/TR][TR][TD]-16[/TD][TD]1[/TD][TD]1-5/16 SAE[/TD][/TR][TR][TD]-20[/TD][TD]1-1/4[/TD][TD]1-5/8 SAE[/TD][/TR][/TABLE]​

NPT Chart

1/8"	0.405"	1.272"	27
1/4"	0.540"	1.696"	18
3/8"	0.675"	2.121"	18
1/2"	0.840"	2.639"	14

<TR bgColor=#eae6e6>[TD] Standard nipples
and pipe sizing: [/TD][/TR]<TR bgColor=#eeeeee>[TD] Pipe Size [/TD][TD] Outside Diameter (O.D.) [/TD][TD] Circumference [/TD][TD] Threads Per Inch [/TD][/TR]

[/TD][/TR]​

[/TABLE]​

 

Love the charts. Now I'm at square one again though. I thought i read somewhere they were AN fittings. Guess that was wrong. Any help is appreciated.

 

The angle of the fittings is the same as AN, 37 degrees. The threads are not. So a flaring tool for AN will work, but AN fittings will not!
Robbie

 

AN and JIC fittings have the same diameter, thread pitch and 37 deg angle for the called out dash number. The only diff is the J class call out on the AN fittings. The only issue I have ever had was I used a AN nut on a JIC fitting. The nut was too deep an I could not properly seat the two 37 deg flares together without the nut bottoming out on the JIC's hex.

Anyway can you post a picture of what you are looking at?

http://www.anplumbing.com/