396 exhaust manifold bolt torque

[Danzo]

Is 25 ft lbs. across the way to go? Also, pros & cons of running gaskets(cast iron head-stock manifolds). Thanks in advance.

[william]

According to the 1969 Chassis Service Manual 20 lbs.-ft. is the spec.

The factory didn't use gaskets but the possibility of warpage exists. Check the flanges with a straight edge to ensure they are uniform.

[firstgenaddict]

According to the 1969 Chassis Service Manual 20 lbs.-ft. is the spec.

The factory didn't use gaskets but the possibility of warpage exists. Check the flanges with a straight edge to ensure they are uniform.

Typically I will draw a flat file across both to ensure the mating surfaces are true, IMHO this is much better than gaskets.
The heat on the exhaust side of the head/exhaust manifold is the highest you will find on the external surfaces of the engine and serves to destroy most gasket materials.

[Rick68]

I took my manifolds to the machine shop.They had a big belt sander and had the mating surfaces sanded flat.When I installed them I used a light coating of Permatex Ultra Copper silicone on the mating surfaces with no gaskets.When the silicone dries you just peel away any excess that oozes out.I torqued the outside pairs at 15-20 ft/lbs with blue Loctite and the inside ones to 30-35ft/lbs and no Loctite.

[Mike S]

I took my manifolds to the machine shop.They had a big belt sander and had the mating surfaces sanded flat.When I installed them I used a light coating of Permatex Ultra Copper silicone on the mating surfaces with no gaskets.When the silicone dries you just peel away any excess that oozes out.I torqued the outside pairs at 15-20 ft/lbs with blue Loctite and the inside ones to 30-35ft/lbs and no Loctite.

Bingo....that's how I did it too, especially the torque on the inside vs. the outside bolts.  The Permatex copper also came highly recommended by some friends who actually used it on their cars but didn't want to use gaskets to seal manifolds that would otherwise always have an ever-so-slightly leak as obvious if the manifold was removed and carbon seen on the flat face.

Mike

[KurtS]

Why different torques?

[Mike S]

I believe it was due to the outside ends using french locks and the inner bolts not.

Mike

[ko-lek-tor]

No 69 BB came with french locks...in a Camaro

[Mike S]

Is that what Danzo has, a 69?

Mike

[bertfam]

The big block french locks were discontinued in late 1967 for the 1968 model year. Although there are a few reported instances where they still showed up in early 1968 production, for the most part, 1967 was the last year for french locks.

Ed

[Mike S]

Hi Ed,
     My 67's have them originally on the February dated MZ and March dated MW motors. I have noticed that the right side 880 manifold has undergone some changes after 67 to add additional webbing in the molding cast. I figured that was to strengthen it because the 880 manifold does look pretty weak on certain spots and I can see how it can warp or crack form the exhaust pipe tugging load. I'm sure they must have cracked during service and it wouldn't surprise me if eliminating the french locks was part of the changes.

Mike