burned valves

[bad440]

my roomate has a 71 swinger daiy driver 6 cyl. it's burned valves twice so far.got an engine from a volare wagon swapped it out,ran real good for a month.then the rough idle crap.gotta tear it down again in a couple of days.so why would this be happening?:banghead:

 

[1970Duster]

not tuned correctly

 

[moper]

Intake leak on those cylinders, tuning, fuel quality...

 

[nuttyprof]

Valves adjusted too tight, if you adjust them till they are quiet they are too tight and will burn.

 

[67Dart273]

Valves too tight, intake leak, carb too lean, engine running way too hot

 

[cudamark]

valves too tight, intake leak, carb too lean, engine running way too hot

x2

 

[BillGrissom]

No suggestions to install hardened valve seats? Shouldn't a Volare head already have them? I had them installed on my 383 heads in 2001 for ~$10/cyl.

 

[bad440]

No suggestions to install hardened valve seats? Shouldn't a Volare head already have them? I had them installed on my 383 heads in 2001 for ~$10/cyl.

winner! took it apart today, #3 and 4 valves sunk seats pretty much gone.valves themselves look ok.all the rest of cyls look good.guess it' s off to the machine shop....