how necessary are these upgrades running 15-20lbs boost ona built bottom end - port and polish, oversized valves, springs retainers. etc? worth it, or overkill? (i'll have the head off anway...)

 

none are NECCESARY, but i would at least go with springs/retainers and valves... its up 2 u though

 

You can run stock head with built bottom end. However you may get more power of the motor if you have the head ported. When a head is ported you are allowing more air to travel at a faster rate. More air, more fuel, more spark = more combustion. Which in turns makes more power.

 

yes, but what about the srtuctural integrity of the stock head components? that is really my main concern.

 

if your going to get the head ported might as well change the springs, retainers etc. Better to be safe then sorry.

 

 

how old is the head?

 

100,000 miles old. last 10,000 were turboed. then piston #4 said ..."good-bye, nice knowing ya..."

but i wonder, could there be any other reason besides a melted piston or broken ring lands causing 50% loss during leakdown test - coming out my valve cover? pffffffffffffffffff

 

bent valve or seat, valve stem seals or guides.
That's a lot of stress on an older stock head.

 

Here is a dyno with a built motor and stock head. I want to say it was at 15psi, but it just may have been at 19psi.
His setup if I remember correctly was:
Drag 3 turbo kit
Thermal 3"
VFAC
RC 370cc injectors
Cartech FMU(set at 6:1)
cam gears
sleaved benson block with 9:1 CR
Stock head

 

hey that was Drag3GSR's dyno.. cam gears and VAFC are fun