My brother told me he heard the later 440 engines used sodium filled valves, and were not designed to run at higher RPM. I bought one from him out of a 78 motor home for my Coronet. Just wanted to comfirm, is this rumor true or is it fake news?

I've never heard of any Mopar engines coming with those valves stock or as a option, I started running and working on Mopar V8 in 1964
The only motors I have ever heard and know that had those valves stock where in the Ford FE 427 race motors for NASCAR
Me thinks your brother is being mislead on this
Mopar made many different versions of H.D. truck, H.D. industrial and marine motors as well as all out race motors, I don't think any of them had those type valves in them from the factory, maybe I'm wrong

I have heard the same as Cab. Never heard of any 440's with them but have heard the Ford 427 FE and maybe the 427 Cammer had them ? Ron

I have a 354 Hemi out of a boat
has a sticker on valve cover
says it has sodium filled valves in it

The early 79 back Ferrari 308 had sodium filled valves and ran high rpm

Only old Mopars with sodium exh valves were extra hd ind engines like a 318-3 with a 7/16 valve stem. Present 6.4L also have them.

The industrial/truck and motor home 413 and 361 motors had sodium filled exhaust valves ....7/16 stem size sounds about right

Damb Doc Im proud of you! A normal reply and it sounds like you really do know your Mopars

Hey HAY .... I always post GEMS !

Maybe he was mis-led by the industrial used one. Thanks for all the information!!

Anyone heard of the present 6.4L having a failure of one of the modern sodium filled valves?

I remember a old time mechanic saying the same thing on the H.D. 354 Hemi truck motors with 1/2 stem valves being sodium filled back then, prior to 1959

Did not know that. Thanks , Ron

So I gotta ask - are they hollow & then filled with sodium? I'm guessing this would reduce operating temp??? Would a "hollow" valve be weaker though? (I'm not an engine guy...)

Yes hollow with huge stems and they lower operating temps H U G E !

The sodium transfers the heat out of the valve on the exhaust and puts it into the guide. Airplanes have been using them since the 30's

Rough rule of thumb used to be that
using a sodium filled exhaust valve
allows about +1 in compression ratio
on the same Octane fuel.

Ford 427s had so many failures of their particular sodium filled valves that the idea got a bad name that has lasted decades.

Lol, TRW is too cheap for a spellchecker.

My old International truck gas 392 had them.

Was there a loose weight/plunger inside to facilitate fluid move?
Thought I remember a click when shaken,

that was the pea rattling around in your head.