Why does the Part's size not change?

function MakeSpark(pos)
	local effect = game.ServerStorage.Part:Clone()
	effect.Name = "Effect"
	effect.Anchored = true
	effect.CanCollide = false
	effect.Material = Enum.Material.SmoothPlastic
	effect.Locked = false
	effect.TopSurface = 0
	effect.BottomSurface = 0
	effect.BrickColor = Colors[1]
	effect.Size = Vector3.new(8, 8, 8) -- This line, doesn't work
	effect.CFrame = CFrame.new(pos)
	effect.Parent = game.Workspace
end

function HitEffect(pos)
		local thread = coroutine.create(MakeSpark)
		coroutine.resume(thread, pos)
	
end

Should make a 8x8x8 part appear.

SImple.

effect.FormFactor=("Custom") 
effect.Size=Vector3.new(8,8,8)

Also line 10 will error.

effect.BrickColor=BrickColor.new("Lime green")

When your using that kind of function function MakeSpark(Pos) you will need to use something like this

--THIS IS NOT THE FUNCTION
MakeSpark(game.Players.LocalPLayer.Character.Torso)