genop

How important is it to match the combustion chamber to the bores? Everyone is always talking about overboring but not many people mention the head....if you dont have it matched to the bores wouldnt that create a bad hot spot? This is just something I have been thinking about, might not even make sense but i'd like to know

earl

I always thought it was better to have the combustion chamber a little smaller than the bore. Anyone want to disagree with me and tell me why it is important to match the chamber to the bore.

hypa

The quench area is very important on a Honda motor, and matching the chamber will cut down on that area, and the overall CR. However, corners and edges could lead to hotspots causing detonation.


I'm not matching my bore when I build my B19c.
I will go through and ensure that there are no places for heat to buildup.

Scott - 93HB Si

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">I always thought it was better to have the combustion chamber a little smaller than the bore. Anyone want to disagree with me and tell me why it is important to match the chamber to the bore.</TD></TR></TABLE>

If you're running an 81mm Combustion Chamber head on an 84mm bore block, you'll have a nice sharpe right angle where the smaller head sits ontop of the larger bore....

Why would having it smaller be better?

genop

If you match it, then you lower the compression.....but couldnt you just run high comp pistons and match it just to be safe?? I guess its not really that much of an issue though since not many people are having it done and their setups work fine.

ZoRG

Would you not pick up more flow from opening up the chamber near the valves? That way you could have the squish as well as some more flow?

SOUNDEFFECTS

THis use to be a huge topic a long time ago when people were just starting to experiment on 84mm bores. Its kinda like having a GSR head instead of a b16 head. Its a smaller quench chamber that has a higher compression rate and supposely promotes better fuel combustion. Less detonation as well according to some of the Honda books I have read because of the design. Also alot of head porters will reconfig a worked head to have a clove leaf type style chamber for the same reason. I remember when portflow was infamous for "opening the chambers to 84mm bore". It was a kinda a band wagon deal that were out slowly and I hear less about it now a days.

Bnjmn

Do research @ http://www.theoldone.com
It isn't a fad and the sharp overhang from an 81mm head on an 84mm bore isn't the best thing for preventing detonation.

Ben