GN block question

[chevy2480]

I forgot to ask, do you know the thread size for the oil return port that I have to ge drilled into the block, pretty soon I'm taking the block to the machine shop and I need to know.

1/2 NPT

 

[87regalkid]

Back to that oil fitting again, is the part that screws in to the block there called the oil drain pipe, or is that something else, I want to try and get this fitting so I can show it to the machine shop, I just can't seem to find it, unless the drain pipe is it.

 

[chevy2480]

The factory return line has a adapter fitting. If you go after market setup then there is no fitting. On my GN the fitting are all part of the Oil return. If you jump on ebay and put in Grand National oil return you will find what your looking for. Just remember if you use the factory type flexable hard line you will need that adapter fitting.

 

[87regalkid]

Thanks, but now I have a different question, I just noticed from some site that you can use an internally balanced flexplate, or an externally balanced one, from the pics, it looks like mine is an external one, can you spread any light on this subject?