Anyone know where I can purchase a brass fitting that threads into a 1972 Turbo 350 for the cooling lines to connect? No local parts store carry "old" stuff. Or have a part number?

 

Would just be buying the entire set of pre-prevent lines be better?

https://www.inlinetube.com/products/...iABEgK-4PD_BwE

 

Maybe this ?

https://www.ctpowertrain.com/350-350...t-th350-th400/

https://www.dormanproducts.com/p-4011-800-755.aspx

This thread might have some useful info:

https://classicoldsmobile.com/forums...itting-183385/

 

The set doesnt have the fittings that screw into the transmission. This is the lines with the fittings on the lines.

 

The fittings dont look the same. These step down in size for one side to the other. Mine is about the same size on both sides.

 

The male end of the fitting in your photo looks like pipe thread.
Something isn't adding up here . . .

 

The factory fitting didnt look like mine? That would mean someone drilled out the hole and tapped it to a new size?

 

Have a look at this post

https://classicoldsmobile.com/forums...5/#post1605759

 

Checking the threads it looks like the fitting might be 5/16 female inverted flare to 5/16 NPT male. Can anyone confirm if this is right?

 

I saw that post for a TH400. Is it possible the 350 and 400 have different male sides?

 

As far as I can remember - the fittings that thread into the aluminum THM transmission cases are straight. There is a washer that is also used.

Here's all that I have for documentation. From TH400 parts book dated 1973.

 

Think I have it right now. I think it should be 1/2 - 20 female inverted flare to 1/4 male NPT. If anyone knows if that is correct, please let me know.

 

My 350 doesnt have the protrusions where the fittings install like the photo. Is that a TH400 pictured?

 

Yes, diagrams are from TH400 parts book dated 1973.

While we wait for others to help - take a look at this link.
https://www.transmissionpartsusa.com...-00035340a.htm

 

This may be the right one?

https://www.inlinetube.com/products/adt16

 

Well I'm stumped. I thought that the connectors were the same for all THM transmissions. It looks like I'm wrong here. Apologies.
Here's some information from the Oldsmobile parts book dated 1980. It shows different part numbers for the connector for TH350 vs the TH400.

 

Yes, the hole in the transmission is 1/4 pipe thread. I can't remember if the case thread is straight or tapered but I'm pretty sure it's tapered. I can't remember the cooling line fitting - it's been a very long time.

You have two options:
1) use a normal 1/4 NPT male to inverted flare adapter, just be extremely careful tightening the fitting because it's extremely easy to crack the case. Pipe dope might be better than teflon tape, just don't use gobs of tape. Take it slow. It's better to have a leak and tighten it than to crank it down and ruin the case. Any parts store with the pull-out trays of fittings will have these. This is what's been linked above from inline tube and transparts. It should be a $2 part.

2) use a straight thread 1/4 NPT adapter that uses a sealing washer against the face of the transmission and the face of the adapter. This is what all aftermarket AN adapters use and what that GM diagram shows. You can crank these down, but they rely on a decently flat face on the transmission and a suitably conformant washer to work. If the trans is in excellent shape then a copper washer works. Most of the kits come with a plastic washer because those are more forgiving, but can tear and fall apart.

This is why most folks don't remove these fittings from the cases unless they're converting to an AN line!

 

Don’t use tapered pipe threads in the case!! More than likely you will crack the case.

I believe it’s 1/4 inch straight pipe, with a copper sealing washer.

 

The fitting he showed in the picture is tapered pipe thread. There is a chance that somebody has screwed up and put that in there or did it as some type of repair.

OP you need to figure out what threads are in your transmission case before you get a fitting. You will not find it in a book. Somebody might have rethreaded it ?

 

If there is anybody that can describe part number 3974421 or show us a photo of what it looks like, then that would be helpful.

According to the Oldsmobile parts book page, above, there are two of them on every TH350 made between 1970 and 1975.

 

I found a fitting local. Thanks for the input from everyone. The case side was male 1/4 pipe thread. The line side is 1/2-20 inverted flare for anyone in the future.