Packard Forum Index » Post-War (1946-54)

I had my exhaust manifold replaced last fall. After a short time the exhaust flange nuts came loose. I went to a muffler shop and after getting a better gasket from Olson’s they were able to get it tight.

Now it has loosened again after a few short drives.
It makes the engine very noisy.

They’re there a special washer to help this.?

I understand that Loctite won’t work because of the extreme heat.

Make sure there is pipe support or hanger at the bell housing as the pipe will always come loose if it is allowed to pivot at the exhaust flange, instead of moving with the engine.

Assuming the replacement manifold isn't damaged or flats rusted/uneven, engine mounts are OK;
If you're re-using the studs and nuts that might be the issue. Corrosion will reduce the size over time just enough to make them "loose"/lose thread engagement %.
Try and replace the studs and nuts with new, if not changed. Be careful always a chance to snap off.
If long enough, might put a split lock washer or spider type under the nuts.
Make sure to torque them, not just tighten.
There's also those lock nuts that have the dimple, not the insert, that may help. But may make it tough to remove later.
The best loctite is rated about 350F, which is borderline but not far off. I don't think a dab would hurt, even if it bakes off over time.
Also other high temps;
vibra-tite.com/threadlockers/high-streng ... reme-high-temperature-threadlocker/

This is the support mentioned and can differ between engines. Sometimes a bolt falls out or the pieces are assembled incorrectly putting strain on the flange. Muffler shops have also removed them and sometimes not replaced with the new exhaust system. There is also a paragraph in the chassis section of the 46-50 service manual on how to neutralize the exhaust system to prevent strain and vibration issues.

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New studs, nuts, and washers are available from Max and Kanter.

IIRC, the nuts are brass to avoid corrosion issues.

I know the washers are hardened and extra-extra-thick, at least for the 288/327. Hardware-store washers, even if hardened, and even if extra-thick, don't work as well.

Even on the later car (51-54), that support is present and runs between connects to a bolt off neat the front side of the transmission.

The only picture I could find when working on my '54 that shows the supports.

The Yellow arrow points at the bracket that mounts off the transmission case. The Orange arrow shows the bracket that mounts to the frame.

It may not be the exact same for your car, but at least it should give you a point of reference.

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1954 exhaust pipes have. Little tab welded onto them in that spot which the 1951-1953 pipes do not have. That’s why 1954 has a different part number but it is otherwise the same.

That said, I’ve always just retorqued them from after a few heat and cool cycles after which they seemed to stay tight.

Yep! They need to be torqued a few times after heat cycles, in the same way as the head gasket does.

Thanks for all of your insightful reply’s..

My friend Richard sent me some lock nuts that I will try tomorrow.

You members are the best!

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Those are Marsden nuts, invented by a Packard employee and are used in many places on Packard. Larger ones are used for the bumper bolts on some models, they are inside Ultramatics and even my Henney-Packards use them for the driveshaft support brackets.