I know milling the heads or the block raises compression? But is there any importance in it? Also is it more important to mill the heads or the block when you rebuild your engine, if you only had one choice?

 

Milling makes sure you (have a for lack of a better word), a true fit. My machine shop told me you are supose to have the aluminum heads milled every time they come off. I personally think they are trying to drum up business for themselves. If you overheated the car, then the aluminum heads more than likely got warped and need to be milled. There are better explanations if it needs to be done every time the heads are pulled. Personally if I haven't overheated the car, I don't think I would have them milled. Unless I knew for fact it had to be done every time. If anyone can confirm or deny this, let us know? I am sure there is a limit to the amount I can take off.

ZMAN

 

Milling the heads makes for a true and perfectly flat mating surface. I would definitely recommend it on the LT1 if you take the heads off seeing as how bad these motors are about blowing head gaskets.

Milling the block also gets a straight and true mating surface in addition to bringing the piston closer to even with the top of the block deck. By bringing the piston top closer to even with the block deck, you decrease the quench area between the piston and head when the motor is assembled.

 

Like FastZnTN said... BOTH!

Decking the block will set up your quench to where you want it while milling the heads will set your chamber volume and make sure that they are flat for proper gasket seal.

Bret

 

You always mill aluminum heads when you take them off. Iron heads you don't have to just take a straight edge shine a light and if goes through the bottom of the straight edge you get them milled.