when you get you block bored out and resleeved, is it critical to get your head matched as well? or does it not matter that much.

I was thinking about getting a GSR block bored and sleeved to 2 liters of displacement and then swapping it into my car.

 

That would mean an 84mm bore, so depending on what pistons you use, and the clearance you'll have between them and the head, it may be a good idea to get the combustion chambers deshrouded to match the pistons. You may be able to get away with leaving the head alone though, it all depends on what kind of clearance you end up with.

 

what do you mean. Ideally, this would be done for a turbo setup. You saying the pistons would have to have a lip on them or something to clear the head? what pistons would I need? and wouldn't this change the compression ratio if the combustion chamber was deshrouded? when pistons are at the top of their stroke, do they extend past the the top of the block into the combustion chamber? I mean I know the have domed pistons with valve recesses in them, but does the edge of the piston extend above the block?

 

You would have to clay check the piston-to-deck height for your particular application. On a stock motor it's like 0.030" between the piston top and the deck.

The issue here is essentially the diameter of the combustion chamber and whether or not the piston is going to smack into it. Since you'll be boring out the cylinders to 84 mm it is possible that even with the same piston-to-deck height, the dome of the piston will have a wide enough diameter to run into clearance problems with the stock combustion chamber. When this is a potential issue you have to reshape the combustion chamber to make room for the piston, this is called deshrouding.

 

I see. is this more trouble then its worth? like, if I just get the block resleeved and leave it a 1.8 liters and boost it, how much of a power gain would I see if I had it bored to 2 liters?