Errr.... Yes, if it is coming out the spark plug holes then as you know the housing is fair thee well flooded with coolant.  So that would lead me to suspect one of these causes (in order of likelihood):

1.  Most likely bad coolant O ring - I presume you are using the Teflon Encapsulated Silicone "O" rings?   Generally only two things make them leak, damage during installation (i.e. perhaps pinched) or over heating (and it takes a whole lot of that - I turned an area of the side housings blue with heat before that O ring failed).  If stock coolant "O" rings were used then they are more easily damaged by over heat and prone to leaking.

2.  Damaged groove in the iron side housing in which the "O" ring fits which then provides a leak path - Hope its not this one as that means a new side housing.  This  is sometime caused by shifts in the casting core when the molten iron is poured in or can be caused by corrosion as these walls are fairly thin.

3.  Intake porting too extreme - leaving too thin a wall of metal between port and coolant galleys. Also requires another sidehousing

4.  Foreign object damage to inside of housing.(punching through into the coolant system - not likely)

I hope its the coolant "O" ring.

Good luck, Dave