Price ranges for SC 3.2
 

1978 SC 167k miles on chassis with a 3.2 liter carrera motor 75k miles.
Rebuilt 915 trans new clutch.

My question is since the 3.0 was replaced with a 3.2 how much value in price is gained/devalued?

A 3.2 in an SC can be a nice upgrade. However, most buyers are looking for originality. If you had two identical 1978 911SCs, like condition in every way (except one had the 3.2) the one with the original 3.0 engine will be worth more every time.

With that many miles on the car, though, it might not matter a whole lot that there is a non original engine in it.

Having the 3.2 is a bonus.

for a driver it's a bonus. For a collector it's a deal breaker. Take your pick.

find the right buyer who appreciates the extra HP and it will sell

It's funny...some guys say " drive it like you stole it! " " Make it your daily driver!" While others say if it has over 150,000 it just will not be worth that much!

I ran into a guy with a guards red perfect 993 two years ago at a vintage car race. His car only had 90,000 miles on it. He said he did not drive it much to keep the miles down.

How often do you see info on milage on 73 RS and other high end longhoods. Just saying.

Miles still matter, but not as much in older cars where rust and (interior, paint and trim) condition are the real issues. I think Porsches should stay original (unless you go all out). Generally I believe that the car should have its original motor, even if it's a hotrod. Best of luck.

The biggest bump in current 911 value is for those with collector value. I've driven both, own a 3.2L, and prefer the 3.2L and Motronic. I turn the key, it starts instantly, and warms up/runs like a modern car. That said, the 3.2L has hurt the value of my car, as it hasn't received the offers lesser 3.0L SC's have closed at either here or on eBay.

@jay
Yes i do enjoy the 3.2 more over the 3.0.