Brass Manifold Nuts and Washers

[squirebill]

So I'm getting ready to build up the 218 short block I had machined and rebuilt.  I remembered about the brass nuts and washers for the manifolds but not about their proper location.  Did the research on this forum and hard copies of manuals I have and have the locations sorted out.  What none of this research has told me is why do these Mopar flatheads have these brass nuts and washers.  Not only that but two different configurations of the nuts and washers (regular washers, "conical" washers, regular nuts, and "conical" nuts).  I'm thinking something to do with thermal expansion of dissimilar metals (cast iron block and manifolds and steel bolts and studs), but just a guess on my part.  Any thoughts from anyone else? Regards to all

[PT81Jan]

Wondered that too, when I got my new nuts and washer sometime ago.

Here my thoughts: Requirement is, that the bolting doesn`t lose its preload to ensure the manifolds doesn`t leak. Parts do expand when getting hot and contract, when getting cold. So the bolting has to compensate that movement.

Bolts / studs are working like a spring when properly tightened. Longer ones do have a better preload=self-lock than short ones.

Assumption: no additional locking precausion needed on the long bolts, so standard washers and nuts are used (red circles). On the other hand a reason to use conical nuts on short bolts (green circle) might be, that not enough self-lock is guaranteed. The slots on those nuts are working like a locking device. The conical washer are needed as a counter part of course.

Remains the question why there are short bolts without conical (lock) nuts: Those with the yellow circle have to hold two manifold flanges. Therefor a washer with a larger diameter is needed. Assuming these are no special made items but standard parts, there doesn`t exist conical washers with a larger diameter. So regular washers and nuts are used. On that with the blue circle there is just not enough space in height to put the conical nut and washer between the manifold flange and wall.

Regarding the different material. Brass parts doesn`t seizure like steel. The conical nuts need to be of steel due to their job working as a spring, too.

Just my assumptions ...

Edited April 11, 2018 by PT81Jan

[Conn47D24]

VERY Timely !

 

I'm just now about to tackle the manifold.

 

These image and post are great !

Thanks for posting.

 

Clay

[ggdad1951]

remember to periodically check those special nuts and washers!  Mine worked their way loose over the course of 5 years and needed a re-snug.

[Don Coatney]

33 minutes ago, ggdad1951 said:

remember to periodically check those special nuts and washers!  Mine worked their way loose over the course of 5 years and needed a re-snug.

 

 

I had the same issue. Found one missing one day. Lucky I had a few spares on hand.

 

 

 

[Merle Coggins]

39 minutes ago, ggdad1951 said:

remember to periodically check those special nuts and washers!  Mine worked their way loose over the course of 5 years and needed a re-snug.

 

I always knew you had a screw loose somewhere... ??