Might be a dumb question but I'm looking for opinions.
I removed an exhaust manifold from my 1975 Ford F350.
The bolts are 3/8" NC x 3/4".
The head of the bolt is not a standard hex head.
It has a 1/2" flange with a 3/8" hex head.
#1 Should I try to find new bolts to reinstall the manifold?
#2 Should I use a high temp anti seize or something similar on the bolts?

 

I'd just cleam them up and put them back in, if you are worried about them working loose just put a little blue loctite on them when installing..

 

The bolt you describe is called a 'flange head' bolt. I can always find them at Lowes (home store) in the hardware section. Some auto parts stores will also carry them. It's wise to use the same type of hardware if possible, the flange of the bolt has serrations on the backside that help keep the bolt from backing off once it gets tightened.

As for anti-seize, I wouldn't use it. Most of them have a temp. range that is within the exhaust manifold temp. range so it will just burn off.

 

I highly disagree and highly recommend applying anti-seize compound. Anti-seize contains ground up glass and, while the liquid will burn off, the ground glass will be left behind and prevent the metals from fully corroding to each other. The micro-gaps in contact allows for easier removal.

I've got a 73 and 70 with FEs. The PO of the 73 applied anti-seize and the manifold bolts came out like butter prior to me installing headers. On the 70, the PO didn't use any and they're rusted and locked in solid. I will not dare attempt to remove them until it is time to do so. Meanwhile, it stays on the road with no exhaust leaks.

 

Feed back, whether it is right or wrong is always welcome.
If you get enough of it from different sources, one can make their own conclusion.


Thanks for your reply. I tend to believe you.
The last thing I would put on an exhaust bolt is lock tight.

I acquired a new set of flange bolts with Black Phosphate & Oil coating.
Every thing else I found had zinc coating.
I could not find any feed back as to how zinc reacts to high temp from an exhaust system.
I have already installed them with high temp anti sieze. Package even suggests using it on exhaust bolts.

I finally put this beast back together and made a test run up.
Nothing Fell off. Engine was runnig very pourly but seems okay after I put some fresh gas in her.

 

Most threadlockers break down at higher temperatures so you'd have trouble getting them to work. Bolts-to-head, however, might get them stuck forever since the head is cooled by engine coolant.

I've actually heard that graphite spray can be used to keep exhaust manifolds looking fresh, and it'll probably work to keep studs from freezing. Anti-seize is the best way to go for bolts going into the head, IMO.