I have an H22A4 and I want to bore it out to 89MM. I have heard that the A4 is an open deck and is not ideal for boring out.

#1, can anyone show me what the open deck configuration looks like. Of course I could take my head off and look, but this is obviously the easier option.

#2, Are there any gains from using an H22A or A1 block vs an A4 block, performance wise.

BTW, I have the 07 version with the 50mm main.

 

Neither are ideal for boring out unless you sleeve them. Both deck types work well for NA, overbored or not. It's when pushing large amounts of boost that most people begin leaning towards closed deck vs. open deck. If you're boosting, I've read that open deck is good to about 15lbs of boost, anything above that & the sleeves may begin to creep on you.

 

the obd2 blocks are open deck....which is better for sleeving in order to get an 89mm bore....im not sure who told you that closed deck was better but its not....

using a 98+ a4 block is the best idea because the mains are larger....im not sure what an 07 version is, but if you have a 97 block already then so what....not a huge deal....

 

ok, Thanks

 

93-97 = 50mm mains
98+ = 55mm mains

 

open deck

H22a4:

engine is easier to re sleeve... but in stock form not as good for boost

Closed Deck
H22a:


better to boost but harder to resleeve...