Ok i blew a head gasket the other day and also need to replace the valve guides. After thinking about doing myself i thought i better not so I took it to Book racing by my house. Well its fairly expensive but they do a great job and their price includes machine work and a valve job along with other little things no one else i talked to mentioned. Anyways since the car will be all apart i decided to get a competition valve job done and some pocket porting. I have a 89 L98 Formula what performance gains will i expect?

 

while you have the heads off port your intake, runners and plenum too. if you do all of that I'd say 25-40hp its kinda hard to say. is everything all stock? also if you put on some SLP,accel,etc runners(if you still have the stock ones) I'd say between 30hp-55hp

Josh