Basically, if you are asking that question, you probably know more than 95% (or more) of Honda tuners. Really, there is more bad info out there on B20’s than anything else. Most people with B20’s have 126hp 8.8:1 JDM B20B's that they spent $1000+ on after installation at a shop.
This is coming from someone who has done extensive research and has a 2001 USDM B20Z that made 146whp/137wtq with the P75 head with only I/H/E (well, the AEM cam gears were turned a little as well - I didn't have any way of adjusting them when it was tuned, so I don't know if that helped or hurt).
The P8R head is said to have "VTEC-sized" intake valves and an 84mm combustion chamber (I don't remember if the exhaust valves are different or not). All B20's use a 84mm headgasket regardless of the head (a 81mm LS headgasket will not work). Here is the breakdown on engines/cams:
1. USDM/JDM 96-98(ish) CRV - 8.8:1, P75 head - 126hp/133tq. Block labeled B20B in Japan and B20B followed by a number in the US. Usually has a very tall LS style intake manifold that is often referred to as a "giraffe" because of the really long runners. (cam specs in the chart below)
2. JDM (the specs listed are from a Honda Orthia - multiple cars came with B20's over in Japan, so there could be other variations) - 9.2:1, P8R head ~ about 143hp/132tq from converting from PS and NM figures that I found in some info on the Orthia. Block labeled B20B. Usually has an LS style intake manifold. Same cams and pistons as the 8.8:1 compression engine based on research done by some guys on nonvtec.com a while back - can't find it now since all of the old stuff got deleted when something happened with the site (was a big sticky with extensive information and actual measurements).
3. USDM/JDM 99-01(ish) CRV - 9.6:1, P75 head - 146hp/133tq. Block labeled B20B in Japan and B20Z2 in the US. Intake manifold looks like an LS manifold with a large funky looking box on the top. Will also have a knock sensor. More lift on intake cam - exact same cams as in the 96-01 Integra B18B (specs in the chart below).
*chart taken from the USDM Honda CRV factory service manual (commonly referred to as a Helm's manual, since they make them)
Basically, all of the exhaust cams are the same, and you want to run a B20Z/B18B intake cam. From what I understood in my research, the engine with the P8R head comes with a special thinner head gasket (2 layer vs. 3 layer) that raises the compression to 9.2:1. If it is truly just the head gasket that accounts for the increase in compression, then you would still have 9.6:1 on the 9.6:1 block. If the head itself raises the compression, then you would end up with 10:1. Get me a P8R head and I'll give you all of the info you could ever wish for including dyno numbers... LOL! If I could find a P8R head (and for a reasonable price), I would do in a heartbeat.
This was with:
2001 USDM Honda CRV B20Z2 (9.6:1cr) engine
YS1 transmission (long-geared 1992 LS) - (now running a Y1 B16 tranny)
K&N cone filter
DC Sports 4-2-1 header,
Thermal R&D catback
Fidanza 8lb flywheel
dyno tune with Chrome
146whp/137wtq ON 87 OCTANE!!!
I got 31mpg with the LS tranny and now get 28-29 wth the B16 tranny and driving the hell out of it on back roads or stuck in traffic.
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