[mykat]

Does anyone know what type/size the threads are on the fuel rail test nipple for a 90 351w? Need to get the right adapter to test fuel pressure.

 

[robbz28]

It's the same size as a your tire valve, so you could take a valve stem cap with you and find an adapter that fits.

Also remember you will need to remove the valve from the middle of the nipple if you plan on running a gauge off of it.

 

[jermil01]

whatever fuel pressure tester kit you buy will come with the right adapter.