Head exhaust valve replacement -valve job

[impala67]

Looked and looked with search but could not find any info about exhaust valve replacement. none.

My background; been using highway daily driver my -91 parkavenue L27 (no supercharger) from 140k to 190k miles.
I have replaced the cam sensor when the magnet was missing and drove ten thousand miles with no major problem. Inspected and tested annually, no problem has ran great -i have always used only syntetic oils and did frequent maintenance.

this year car failed emission test, car has had slight misfire at idle ca. 800-900rpm.
First i replaced upper intake gasket. didnt help, changed Idle air intake valve (IACV) at throttle body, no difference.
I had to replace the cat to get to limits. cat was original (!).
My mechanic suspected that since it still kind of misfires at idle - that number #1 cylinder exhaust valve might be leaking.

So for the next longer pause in traffic i am getting ready to do the head valve replacement job.
Has anyone done valve jobs? I quess if i pull the heads out, same time atleast lifters is worth changing as well as most of exhaust valves. or should i just change the ones that have out of factory manul (FSM) limits...and should i replace injectors while i am at it?
-Is it the best bet to buy only sealed power valves or are the aftermarket ones "as good"...

thanks for comments and stories

[crash93ssei]

You haven't found any info on it because that is never an issue on these engines, the valves are pretty much good for the life of the engine for normal driving. Have your mechanic do a compression test, that will tell you if it has a bad valve.

[J Wikoff]

Compression test is a good idea.

I have read vague references of early L27's without EGRs "burning" exhaust valves. What exactly that means, I don't know. They are old references at that. I haven't seen anyone here talking about it.

[MattStrike]

Make sure they do both compression and leak-down tests.
http://en.wikipedia.org/wiki/Leak-down_tester

[Jrs3800]

Compression test is a good idea.

I have read vague references of early L27's without EGRs "burning" exhaust valves. What exactly that means, I don't know. They are old references at that. I haven't seen anyone here talking about it.

I agree on the compression test... Make sure before you go pulling it apart..

The EGR'less L27 and the LN7 3300 had issues with burning exhaust valves as the combustion temps were a bit higher.. The 3800 and 3300 didn't need an EGR to pass emissions( yes they were that clean ).. so for 91-92 for the L27 and 89-93 for the 3300 there was no EGR used.. They found that they had Burnt Exhaust valves and a lot of cracked exhaust manifolds showing up.. so for the 93 Model year the EGR was added back in as part of the correction..

It was still rare for the 3300 or 3800 to burn an exhaust valve but over the years I have seen this happen a handful of times..

[impala67]

Yes, i should be more accurate. they did come to conclusion after testing. So this just isnt a regular problem and sounds like its a defect i need to repair. Car is now again inspected and with new cat, it does not NEED the head job... but I am planning to do it to improve occasionally misfiring idle when hot. Thanks for comments folks.