Re: 1937 120c 282ci rear coolant drain type?

Posted by DavidPackard On 2022/9/3 22:06:06

That should be 1/8 – 27 tapered. 1/8 National Pipe Thread Tapered –(NPT).

The non-tapered version is referred to as National Pipe Tread Straight (NPTS), and does not have the necessary interference that forms the seal. The 1/8 -28 is likely an ISO standard typically not used in the US, but I have seen it in ‘foreign’ cars. The British Standard Pipe Taper (BSPT) is also 28 TPI, plus the thread geometry is not the same as the US standard . . . that too is not likely to seal.

In 1937 I would expect 1/8 – 27 NPT. See group 50.720 in the Utility section of the parts list.

dp