273 exhaust manifold bolts. Sealant or no?

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Wally-T

Wally-T

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Back again folks!
I noticed on my 1964 273ci that the exhaust manifold bolt thread bores aren't sealed from the water jackets in the heads. I used some Permatex silicone on them but I'm thinking it's too hot for that stuff.
I'm also wondering what the connical washers on the exhaust bolts are for. Maybe to prevent the bolts from snapping because of hot/cold cycles?
Thanks for any help.
Wally.
 
The washers provide for expansion (and the foil exhaust manifold gaskets go on only one way to enable the manifold to "slip" a little during heating and cooling expansion/contraction). The end studs/bolts do require a sealant because of the water jacket.

When I first installed a rebuilt small block in my '65 Barracuda, I could hear a "sizzling" noise when I shut off the engine. I later found that the rear passenger side exhaust manifold stud was not sealed and the noise was a mini-leak (maybe steam) coming from that fastener that required some or more sealant.

I believe the factory did not use the special washers on the two center manifold bolts (only on the other four outer ones), although I find "kits" sold online provide the washers for all the fasteners.
 
dibbons said:
The washers provide for expansion (and the foil exhaust manifold gaskets go on only one way to enable the manifold to "slip" a little during heating and cooling expansion/contraction). The end studs/bolts do require a sealant because of the water jacket.

When I first installed a rebuilt small block in my '65 Barracuda, I could hear a "sizzling" noise when I shut off the engine. I later found that the rear passenger side exhaust manifold stud was not sealed and the noise was a mini-leak (maybe steam) coming from that fastener that required some or more sealant.

I believe the factory did not use the special washers on the two center manifold bolts (only on the other four outer ones), although I find "kits" sold online provide the washers for all the fasteners.
Click to expand...
Thanks dibbons. Do you think the Permatex will do?
 
Black or copper rtv will work just fine to steal those bolts. Blue would probably work too but I would use the black or the copper.
 
I use RTV red threadlocker on the outer studs to seal them in the head. I also use CopperCoat on the gaskets. I haven't found a silicone that will hold up to exhaust temps. I put the conical washers under all the fasteners along with NeverSieze on the threads.
 
cudamark said:
I use RTV red threadlocker on the outer studs to seal them in the head. I also use CopperCoat on the gaskets. I haven't found a silicone that will hold up to exhaust temps. I put the conical washers under all the fasteners along with NeverSieze on the threads.
Click to expand...
Permatex 81422 Good to 650°

81422 permatex.jpg
 
Just did this to my new 318, used Permatex hi temp Teflon thread sealant. Many other sealants will do the job. Just make sure that it is dry and clean. Let it sit for a day before coolant and start up.
 
They got a new red sealant that is 750F iirc it's $12 a tube. Sitting at home in my garage....
 
dibbons said:
The washers provide for expansion (and the foil exhaust manifold gaskets go on only one way to enable the manifold to "slip" a little during heating and cooling expansion/contraction). The end studs/bolts do require a sealant because of the water jacket.

When I first installed a rebuilt small block in my '65 Barracuda, I could hear a "sizzling" noise when I shut off the engine. I later found that the rear passenger side exhaust manifold stud was not sealed and the noise was a mini-leak (maybe steam) coming from that fastener that required some or more sealant.

I believe the factory did not use the special washers on the two center manifold bolts (only on the other four outer ones), although I find "kits" sold online provide the washers for all the fasteners.
Click to expand...

So only the end bolts need sealant for all the factory cast iron heads?
 
I suppose it would not hurt to use something like anti-seize on the other inner bolts to make it less likely to break off a bolt during the next dis-assembly.
 
The outer bolts, almost any sealer will work, from common pipe "dope" to teflon to RTV to ...whatever. So far as I know, al Mopar wedge engines, either SB or B/RB must have the outer two manifold bolts sealed
 
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