I am going 84mm. Does anything need to be done to the head? Or can it stay how it is?

i heard you have to open up the chamber on the head to 84mm or some **** like that. Is that true or can it stay the same?

 

the head can stay like that, look at the b20...

 

if you open it up you will loose compression but i heard of people doing it. not sure y but bump to find out.

 

What will happen if I don't open it up?

I know for a fact that the b20 's head is 81mm while the block is 84mm. Why didn't honda modify the ls head cast.

Has anyone experienced detonation on a stock motor turbo b20?

 

for simple stock b20/vtec you don;t need to open head, it will not help anything except cause you to lower compression. The issue you are prolly thinking about is the valve reliefs on the stock b20 pistons are small and the lift on the secondary VTEC cam (the bigger lobe) can cause severe v-to-p clearance due to the lack of b20 piston's valve reliefs.

As for when people open up the chamber in heads, mostly from bigger dome aftermarket pistons with much bigger bores and where domes actually come out to the edge of the piston then the head chamber needs to be opened up to accomodate the piston. an example is Endyn's 86mm gas port custom pistons ===> head chamber has to be opened up to at least 84.5mm

hth,
Greg

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CHEETAH &raquo;</TD></TR><TR><TD CLASS="quote">for simple stock b20/vtec you don;t need to open head, it will not help anything except cause you to lower compression. The issue you are prolly thinking about is the valve reliefs on the stock b20 pistons are small and the lift on the secondary VTEC cam (the bigger lobe) can cause severe v-to-p clearance due to the lack of b20 piston's valve reliefs.

As for when people open up the chamber in heads, mostly from bigger dome aftermarket pistons with much bigger bores and where domes actually come out to the edge of the piston then the head chamber needs to be opened up to accomodate the piston. an example is Endyn's 86mm gas port custom pistons ===&gt; head chamber has to be opened up to at least 84.5mm

hth,
Greg</TD></TR></TABLE>

So the head only needs to be opened up if necessary due to the piston? By the way. it is not a b20 it is a sleeved gs-r b18c1 bottom if that makes a difference. Not sure on the piston or compression I will be using yet.

I heard that if you don't open up the head that the overlap on the head from the sharp edges causes detonation. Is that true?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FastAssEG &raquo;</TD></TR><TR><TD CLASS="quote">

So the head only needs to be opened up if necessary due to the piston? By the way. it is not a b20 it is a sleeved gs-r b18c1 bottom if that makes a difference. Not sure on the piston or compression I will be using yet.

I heard that if you don't open up the head that the overlap on the head from the sharp edges causes detonation. Is that true?</TD></TR></TABLE>

no its a rumor, the chamber is much smaller than stock 81mm yet it works fine on stock motors.

Like I said open the cahmber based on the pistons you will use.

greg

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CHEETAH &raquo;</TD></TR><TR><TD CLASS="quote">

no its a rumor, the chamber is much smaller than stock 81mm yet it works fine on stock motors.

Like I said open the chamber based on the pistons you will use.

greg</TD></TR></TABLE>

So, I don't have to open up the head chamber unless the piston I use requires it due to clearance issues.

How would I know if the chamber of the head needs to be opened with the psiton I purchase?

 

it kinda makes sense to open the chambers on high compression because it is leaving a sharp edge in there to create detonation a little, i didnt do it on my at 12-1cr and it was fine

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by warwagon &raquo;</TD></TR><TR><TD CLASS="quote">it kinda makes sense to open the chambers on high compression because it is leaving a sharp edge in there to create detonation a little, i didnt do it on my at 12-1cr and it was fine </TD></TR></TABLE>

What bore was your motor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FastAssEG &raquo;</TD></TR><TR><TD CLASS="quote">

What bore was your motor?</TD></TR></TABLE>

84.5