how much is the average price to do head machining or is it better to go ahead just buy different springs that dont require no head machining , I have a 986 springs and they do required to get the head machining and by the way I have a cc306 cam.let me know thanks

 

I have fixed these springs on 2 sets of LT1 heads without head machining, you just have to use the propper seat (I think its pn 4771-16) and notch it at the valve cover bolt boss, nothing major just a simple simple notch using bench grinder or even a file.
On my LT4 heads I used the 987 set which is dimentianaly the same, but the LT4 raised runners needed the machining, and I used a spring seat cutter (about $70) and done both heads in about 30 min.

 

where can I get that seat pn#(4771-16)

thanks

 

Its a comp cams part, summit and jegs carry them.

 

I just check the part number at jegs and summit and its not valid.

 

When you check for the P/N on summit etc. you'll need to add their prefix for that particular manufacturer, i.e. "CCA-4771-16"

Opening up spring seats generally isnt too expensive, and if the heads are off the car I'd go ahead & spend the ~$35 to do it and not have to go through the hassle of doing it in the future. That and you're obviously limiting your spring selection to try to save a few $, which isn't worth the savings in alot of cases IMO. YMMV

 

If you're looking at going with dual springs, the Crane 99893's will work without any machining...