Does dohc swap raise compression?

[tom04841]

Just as the title states? I have a head and 2g ecu on the way, but am curious if the head swap raises the compression?

[mysticj]

which head are you talking about? the 1G, 2G, 4G67/G4CN, or 4G61/G4GR?

The 1G/2G have combustion chambers at 47cc .
The 4G67/4G61 have combustion chambers at 43cc.
The 1G and 4G67 have the same intake ports.
The 2G and 4G61 have about the same intake ports.
The 4G64 heads are 47cc so adding the 1G/2G heads won't increase or decrease the compression, the 4G67/4G61 heads will increase compression by .4 to .5

[evil-G-nius]

Thats assuming you dont change the pistons...you can buy higher compression pistons to raise it. The GS comes stock with....10:1 I think and the SOHC is 9.5:1 I think (dont quote me 100%)

[tom04841]

thanks for the reply. my problem is finding pistons to actually lower compression for going turbo. The lowest i can find is 9:1. I was looking for something like 8.5:1

[laxinwarrior]

Mostly any shop that works with DSM's can get you the pistons you are looking for and they usually will even be able to get them in custom CR's if you ask for them.