Lock Washers on Exhaust Manifold Bolts?

I would presume lock washers probably won't hold their properties too well when heated up to 600+ degrees. Spring metal probably wouldn't like being heated and cooled to extremes over and over and probably negates any locking abilities it has. Most likely why I have never seen lock washers on exhaust fittings in automotive or marine environments.

Probably not worth the thoughts you have already spent on it,

Check the bolts once a year and you should be fine, I haven't had one I have installed back out ever. Most importantly recheck the torque after your first full heat cycle (operating temp then cool off over night).

Also, I prefer to use the steel cored graphite coated gaskets, I have never had one of those fail and generally they are reusable if you don't tear them up taking them off. I don't care for the old aluminum crush style perforated/paper gaskets.

A seal that doesn't seal is no seal at all, and certainly undesireable.

Well yea any seal you seal is worth sealing good. Not all are critical though.

There is water transfer between the riser and manifold.

There is no water transfer between manifold and head.

When you have water transfer, especially with gas transfer across the same plane, you need a good seal.

Should I install lock washers on my Exhaust Manifold Bolts?   Will the heat of the engine allow the lock washer to work (lose there spring tension)? The original bolts had lock washers on them. I order new manifolds and a manifold service kit and it didn't include washer for the manifold bolts.   It did include lock washers for the riser bolts.