Noyzee

iTrader: (37)

I got a set of heads from GTP about 3 years ago. they came with dual springs. 987's i believe. they are the springs that require some head machine work.
1st question, are they 987's?
2nd, what is involed in machine work?
thanks alot

Kurtomac

iTrader: (5)

theyre either 987s 978s or 977s all 1.45 dia springs......stock is around 1.29 i think..... all they do is open up the spring pocket diameter wise....im fairly certain they dont mill down in the head any....FYI i recently replaced my 15k mile 987s with stock diameter PRC duals.....i did no shimming just installed the seats seals springs and retainers and all came out to close to 1.80 install height, dynoed them and everything looked good till 6800

Noyzee

iTrader: (37)

cool, thanks. i know i had them in my GTP's, but sold them, and im tring to sell the springs now, but dont know exactly what they will need