hardened valve seats

[Rolling_Thunder]

so I have 4 sets of 346 Heads (1971-1974 400/440) and was wondering if they are already equipped with hardened valve seats - I'm betting on no but I am not sure

[Nacho-RT74]

I think they are, not like the 452s, but they are... wait for more answers to confirm

[Rolling_Thunder]

well these heads either go in the dumpster tomarrow or to my garage...    so the sooner someone can confirm either way the better...     I know they came off of running engines but if they dont have hardened seats no sense keeping them - new seats and valves will cost as much as stealth heads from 440 source   haha

[captnsim]

Those are not hardened seats. The 346 was considered a smog head due to the intake port design. I don't think I'd toss them though. Would make great practice heads for porting...

[RD]

they had a "semi-hardened" design to them.. but not a full hardening.  that is what i have read at least.  I have a set of 346's on my charger right now.  ran them for years w/o the "leaded" gas.  when they were rebuilt by my machine shop, they said that none of the valves were sunk in.  must have done something right ol mopar did.

[Rolling_Thunder]

Maybe I'll keep a pair or two in that case...     

[The70RT]

Has anyone had much trouble with non hardened seats on the street?. The last time I took a set in, my machinest told me after they go through heat cycles for years they harden up. It was a set of power pack heads I had. I sold the car now and didn't put many miles on it so never really tested them. The heads had like 90K on them and the seats were fine before the valve job. 

[b5blue]

They are hardened by induction, not by inserting rings. If they haven't been cut a bunch you should be OK!

[Nacho-RT74]

They are hardened by induction, not by inserting rings. If they haven't been cut a bunch you should be OK!

452s too, but maybe in a deeper process or another technique

[RD]

*edit* nvm, found the links:

http://www.moparmusclemagazine.com/techarticles/5115_cylinder_heads/index.html
http://www.moparmusclemagazine.com/techarticles/5118_cylinder_heads_ii/index.html
http://www.moparmusclemagazine.com/techarticles/5120_cylinder_heads_iii/index.html

[RD]

i stand corrected, they flowed better than all (except 906) in stock intake airflow (upto .500 lift then comparable with all above that) and better than all (including the 906) in stock exhaust airflow (up to .600 lift).

[RECHRGD]

I had 346's on my car until I switched to aluminum heads last year.  I put over 25K miles on them with unleaded and no problems.  I remember years ago, somebody on moparts stated that not all of the 346's had gone through a hardening process.  The only way to tell was that if the heads had two raised parallel lines on one end of the head (mine did) then they were hardened.  I have no idea if that is correct or not though.  Bob

[firefighter3931]

They are hardened by induction, not by inserting rings. If they haven't been cut a bunch you should be OK!

That is correct...the 346 castings are flame hardened and work well with unleaded fuel. 


Ron

[Rolling_Thunder]

Awesome!  I'll snag a couple pairs...