Sullyvette

But really, what is the nut size on a 1965 manifold exhaust stud. I found out I found out I was missing two nuts from the drivers side exhaust manifold. Could they be 3/8th's? And are they brass?


As always, Thanks, Sully

Yes, I looked in a few Corvette parts catalogs, but they don't give the size!

jim lockwood

The nuts which hold the exhaust pipe to the manifold are 3/8-16. From the factory they are steel, but brass is a popular replacement material. One caution.... brass has natural lubricity and can work loose yet it's too soft to really torque tight without distorting the threads.

Easy Rhino

And black anodized brass looks a lot like a steel fastener until you disturb the finish and see brass color. Over about 450 degrees brass becomes extremely soft and the threads will pull out. Don't try to work brass hot, as it will easily gall. You can get brass fasteners to hold a certain amount of cold torque, but when it heats up it will slip (thread tear out).

MikeM

I've used the long brass nuts with success on pipes with the doughnut packing.

Run the nuts up tight. Run the exhaust through a heat cycle. Tighten the nuts again and use a driver bar to hammer against the pipe collar then tighten the nuts again. I agree, they do seem to loosen if you run them up tight just once.

In my experience, the long brass nuts will not strip with the appropriate amount of torque on them. No problem with taking them off years later.

Roger Walling

Isn't there a story about a monkey with brass b...

Sullyvette

I have a terrible habit of over cranking things! SNAP #%$#%$
Does it look snug enough. No movement now. Thx, Sully

Easy Rhino

Pretty tidy looking installation there, Sully.

Unrelated Wiki story about brass nuts:

In October 1990, USS IWO JIMA was in the Persian Gulf, as part of the buildup for Operation Desert Shield. Having been in operation there for two months, she had developed a leak in a steam valve which supplied steam to a stand-by electrical generator. She docked in Manama, Bahrain, where the valve was repaired by a local contractor under US government inspection.

Repairs were completed towards the end of October. On 30 October, as she raised steam to get underway and rejoin the fleet, the valve began to leak once more. The bonnet blew off the valve, flooding the boiler room with steam from two boilers. Ten of the eleven crewmen in the room were killed.

The cause of the accident was determined to be the use of fasteners of the wrong material (namely black oxide coated brass) on the valve, combined with a lack of proper inspection.

Kerrmudgeon

Those are double brass nuts above which would be a lot less likely to strip out. I've always used brass nuts on the collectors but NEVER on the manifold to head bolts....to soft when hot.
Use brass on the collectors if you plan on taking it apart often, as steel will cease up after a few years.