tcervinsky wrote:This is probably a dumb question, but I can't seem to locate all my retainer rings (or washers) that hold the intake and exhaust manifolds to the head. I have new bolts though. Does anyone know if they are available in stainless steel? If so, for where? Or are these a dealer only item?
Thanks for the help.
Are you talking about the bowl-shaped washers under the screw heads?
If so, use Belleville spring washers to replace them. They're there for a reason (has to do with differential expansion rates of aluminum and iron,) so you want to keep or replace them. They're a sort of "mock Belleville" washer - they're not spring-tempered like true Bellevilles, but the shape gives the room needed. I believe the typical Belleville would need to be used in pairs (nested, or "in parallel") to get enough spring tension to clamp, but not so much as to eliminate the spring effect (I haven't checked yet.)
Preload torque doesn't change with the use of Bellevilles. There is /one/ grade of LocTite that will work, I believe it's #277 (maybe #271?) Everyone else will break down with the heat of exhaust, and be useless.
As far as material, using brass or bronze for these screws is preferred. Even CRES will gall against the iron head, and any iron alloy will get progressively weaker over repeated heat cycles. The response of cuprous alloys to heat cycling is opposite to that of ferrous alloys, and they'll gradually get stronger over time (when you remove them, heat them to a "just red" with your torch and drop them into hot water, about boiling - this will bring them back down to a "half hard" condition and allow you to start over again.)
Corrosion is also accelerated significantly by heat, which is why I also use brass hardware for undercar exhaust attachments. Makes it far easier to remove them for service in the future (carbon steel is used because it's cheaper and because OEMs don't want to complicate their logistical trains. Very little of the hardware on vehicles I overhaul ends up being OEM equivalent - or even OEM material! There are usually plenty of better choices out there, OEMs are notoriously cheap...)