What would happen if...

[ThatOneEuroE30]

so I'm parting out my m20b20 and sold the 731 and stuff. Im gonna strip it to the block and then just shove the block into storage until i find a good looking 2002 to slap it in. Any ways my block is only bored to 2.0 liters i was wondering what would happen if i put an 885 head on it with out boring it to 2.5? I'll bore it if its the best choice I'm just curious as to what would happen.

[digger]

It would lower the CR and the overhang due to 80mm bore vs head designed for 84mm would not be good for the burn efficiency as you would have some added areas around the circumference that don’t burn properly, the inlet valve would get close to the edge of the bore but probably not quite hit though I don’t have one in front of me to check. I would say the bigger valve found in the 885 head valve would be somewhat shrouded. I wouldn’t do it personally though if there were not clashes it would probably function.

[ThatOneEuroE30]

So If bore could I put a 885 head on it. If I have to bore it's goin more then 2.5 haha like 2.8

[digger]

So If bore could I put a 885 head on it. If I have to bore it's goin more then 2.5 haha like 2.8

It is common the UK to bore the 80mm (m20b20/b23) blocks out to 84mm. I would use an 84mm (m20b25/b27) bored block if I wanted more than 84mm bore.
You need a M52B28 crank to make a 2.8L with 84mm bore.

[ThatOneEuroE30]

That's what I'll do then thank you.