I have a 86 hydro head from a 1.6 na.Im running a turbo now and was wondering about the valves.Ive heard that the hydro. heads are same spec as turbo after 86...."including exhaust valves?"If so would the valves i have in there be any ok to use if i lapp them?i was wondering about all the heat/cooling processes theyve undergone over the years.will this weaken the metals???