I'm looking at replaceing my leaky factory oil cooler lines with standard hydraulic hose and fittings instead. I'm pretty sure the fittings in the engine block are 3/8" NPT. What are the fittings at the oil cooler? Are they 3/8" NPT also?

I'm looking at replaceing my leaky factory oil cooler lines with standard hydraulic hose and fittings instead. I'm pretty sure the fittings in the engine block are 3/8" NPT. What are the fittings at the oil cooler? Are they 3/8" NPT also?

No, they are some kind of GM tube thread and they seal with O rings. You can find adapters, but you have to look to find them. I bought a new Long Tru-Cool oil cooler with 1/2" pipe thread and used AN adapter fittings. Long is the OEM supplier and it fits right in.

If a standard O-ring fitting wont work then I'll just have a hose shop use my factory ends and add an NPT fitting to turn them into adaptors. Thanks for the help.

I would personally do what bobbie suggested and get a Tru-Cool oil cooler... Much better then trying to mess with adapters from the stock GM oil cooler to whatever fitting size you want for the lines.. But thats me lol.