Building a PR4 head (b18a1) to compare to P8R head (b20 out of Honda Orthia).

PR4 Head:
bore=81mm
flows at 197cfm
combustion chamber volume=45cc
stroke=89mm
intake valve size=31.0mm
exhaust valve size=28.0mm

P8R Head:
bore=84mm
flows at 226cfm
combustion chamber volume=47cc
stroke=89mm I believe
intake valve size=33.0mm
exhaust valve size=28.0mm

Question about compression and air flow....
Have the PR4 head and putting 33mm vtec intake valves only in it (cutting the valve seats).
It's going into a head with a combustion chamber of 45cc. (Which would be a smaller space than the P8R head with the same intake valve size.) First question: since the combustion chamber size is smaller with the 33mm intake valves, wouldn't this be more compression and better air flow? Or not?
Also doesn't the dome size of the piston effect this as well? And how? I want to get technical with all the numbers but am not sure how to. Please help.

there is a link on c-speedracing.com that will help you with compression and other things to determine approx. the characteristics of your motor.

the only thing about 33mm size valves is that if the pistons only accept 31mm and you have a big cam...the valves could nick the pistons a little bit

Thanks for the link...I went to it. Its just like zealautowerks.com. But neither are technical enough for me lol. I think Im thinking too hard!! Honestly its my fiance and his friend who are building this head and I am trying to find what would be the best to do to it. And they are wanting to put p72-00 pistons and some brian crower stage 2 or 404 cams and the 33mm vtec valves and cut the seats. But i am trying to figure out with the larger valves, in the 81mm bore combustion chamber will be good along with p72-00 pistons and possible cams. They are trying to mimmick the honda orthia p8r head. it is a b20 head that has a 84mm bore and 33mm valves. but since it has a 84mm bore, and this one has 81mm bore......just my mind is on overload with numbers lol!!!

if they are oem p72 pistons it should be fine considering the p72 pistons i believe come in the GSR motor... i would honestly recommend them getting some pistons that are higher compression (JDM ITR/B16). or get some forged pistons that you know for sure can handle the bigger valves...the only OEM honda pistons that i know will have a problem is the CTR pistons b/c of the high compression

what would you think on the pr3 or p30 pistons?

use the p30 pistons, they will yield more compression and have the valve pockets to accompany 33mm valves

p30=6.93cc dome/30.00mm comp height
p72-00=2.25cc dome/30.05mm comp height
stock pr4=-3.20cc dome/30.00mm comp height

So I see a pattern.....are you the p30's have a larger cc dome. Is this good for this setup I take it? And how so? How does that cc dome affect the combustion chamber? How does it affect it with the larger valves?

I also see that the p30 has 30mm comp height while the jdm gsr's has the 30.05mm comp height. Would it be best for the 30mm comp height as you said in the p30's? And why? Also how will that affect the combustion chamber?

Will any of this affect the combustion chamber too much?

the dome size is going to get you the compression...bigger dome = higher compression... the comp height should not affect the combustion chamber

do the p30's have too much dome? piston-to-valve clearance....

the dome should be fine..i know ppl that have p30 pistons and crower stage 3 cams with no problems... the only piston that i know of that could create problems on piston to valve clearance is the CTR piston