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Do the brass exhaust manifold nuts use steele washers? Flat, locking or both?

also what is the tightening torque on the manifold nuts? any special sequence for tightening?

I have a 533 which I have owned and driven regularly since 1974. I would suggest 25 fl/lbs would be about right. The theory is that the exhaust manifold, which heats considerably more than the inlet part of the manifold set is able to slide over the manifold gasket without gripping the gasket. You may use manifold sealant on the inwards side of the gasket but you should not use any sealant on the outer side of the manifold gasket. Tightening sequence is optional. Tightening from inside to outside appears logical to me in ironing out the gasket. Flat steel washers should be ok . I have not found it necessary to use lock washers..... Works for me. PT

The parts book lists a flat washer, lock washer and nut.

As for torque, the recommended hand wrench is 6 inches long so not a lot of torque is required.

The ASTM specification for 5/16 - 24 grade 2 is only 13 ft lbs. If you use anti-seize on the nuts the clamping force will be increased significantly.

This is contingent on a planed manifold surface. Those manifolds are very sturdy, however too much torque will distort the block. The exhaust system pressure is around 7 psi.

This topic makes me wonder is some of these cracked blocks are the result of too much stress from those manifolds.

Here in Detroit they have all sorts of ways to determine torque values and they still come up with some totally crazy stuff that snaps bolts during testing.

Does the parts book give any details about the lock washer???? I would be most surprised if it is a common split ring spring steel lock washer due to the heat of the mainifold.

I would be most surprised if it is a common split ring spring steel lock washer due to the heat of the mainifold.

I don't think there is any support for concern about the effect of heat on washers. Just browsing various parts lists between the early 30s and 1954, where lock washers are specified there is no notation of anything special about them. Exhaust manifold heat control valve hardware including wire springs, washers, etc. are just normal hardware, ditto for some automatic choke pot parts and none of them seem to deteriorate due to heat. Manifold studs have the benefit of their attachment to the engine block which is a huge heat sink at far lower temperature than the manifold itself.

Parts manual calls for 5/16 steel lock washers with 7405 brass nut 5/16x24. Overhaul manual just says "be sure all exhaust nuts are pulled up tight to prevent air leaks"

There is no indication of tightening sequence or torque.

Torque specifications didn't really begin to arrive until the late 30s. Prior to that what you'll often find comments such as "use a 6 inch wrench and tighten snugly", or similar.

The most important things to remember on exhaust manifolds is that, as Tim points out, exhaust gas pressures are quite low and the manifold expands more than the cylinder block and thus needs to be tight enough to prevent leaks but not so tight it can't "walk" thru the expansion/contraction cycles. I don't use a torque wrench on manifolds but rather do it by feel, if I did I'd think something like 7-10 ft.-lbs would be quite adequate assuming the manifold surfaces are flat and conform well to the block. As to sequence, common sense says to start in the center and work towards the ends but I rather doubt it's all that important.

found black steel split lock washers and brass nuts at Ace hardware. Special tool handle in the overhaul book looks like you cannot place much torque on the nuts so 'snug up so as to prevent leaks" looks good.