sunderlandmorrow

Hello, I am struggling to find the correct fitting for a 1964 Oldsmobile 330. The original fitting was horribly rusted and I was able to get it removed:

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Unfortunately, the original manifold cracked and I could not reuse it. So I do have a spare fitting but I am having a hell of a time trying to remove that one. I don't think I'll be able to do it without ruining it:

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Now the fitting has to be the same because I know if you increase the diameter the heater core will blow up. I noticed some other forum members experienced that. So here is the inside of the fitting, there is a reducer:

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The ones I found on ebay are not correct, they are a larger thread:

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Anyways, does anyone know how to get the correct part? I suppose I could just get a standard fitting and make my own restrictor in the hose. Thank you

BSiegPaint

I used the reproduction fitting and tapped the hole in the manifold to match. Worked perfectly. I believe the manifold threads are tapered, where the reproduction fitting is not, which is why they don't fit.

Sugar Bear

Heat the old fitting, soak it while hot with PB Blaster or Kroil (watch for fire), lightly tap it, let it cool. Repeat, repeat and repeat.

Good luck!!!

oldcutlass

You actually want to heat the manifold surface surrounding the fitting, not the fitting. Heating the fitting just makes it expand tighter. Try removing the fitting while the manifold is cherry red just below the fitting.

Fun71

My research shows the 1964 engines used a 3/8” pipe thread fitting. Most of the early (1970-older) engines used a 1/2” pipe thread fitting and the later (1971-up) engines used a larger fitting (3/4” pipe thread). So yeah, that listing is wrong for your application.

As you said, you can get a 3/8” pipe thread fitting and make a restriction with a 1/4” hole to reduce the coolant flow rate.

Sugar Bear

oldcutlass is correct, heat the manifold so it expands. The idea of heating it and then soaking it is so that the penetrant gets wicked in as it cools.

fleming442

Blow up the heater core, huh? That's a new one on me!

Fun71

I lost 3 heater cores from running a fitting with no restriction in it, until I finally became aware of what was happening. One back in the mid-90s failed on the very first 5000 RPM pull after installing the new core. Boy was I mad about having to go back in and replace it again so soon. Now that I realized the restriction is necessary and installed one, no heater core failures in a long time and many 5000+ RPM pulls. With no restriction, the volume of coolant flowing through the tubes in the core causes them to swell to the point of splitting. This is what I deduced based on examination of the failed cores.

Yellowstatue

^^^ The core will also hum nicely.

Fun71

Yes, you are correct about that. I had forgotten that it made a lot of noise, like rushing water.

fleming442

Mine sees 6000 often, and it just went after 20 years. 3/4" pipe nipple is in the intake with no restriction other than the heater core itself.