Building a P8R head - Honda-Tech


Building a P8R head

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Old 10-30-2009, 09:32 PM   #1
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Default Building a P8R head

Here's the thing:

1 97 P8R B20 head, (the one with the 33mm in valves, and 28mm ex)
I am confused on the parts I should buy. I looked at a couple of sites, and have found nothing. When buying valve stem seals, will the regular B18a/b,
B20b seals work? When buying new valves, do I buy the Vtec, (I think they are the same size) or the non-vtec valves? When I do put it back together, do I have to take it to a machine shop to get the valves lapped so it sits against the seats? Any help will be greatly apreciated.
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Old 10-31-2009, 12:21 AM   #2
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Default Re: Building a P8R head

i belive so, you will have to degree the cams in as well, not 100% sure but i think so, I would just drop the head off at a local machine shop, and have them assemble it and maybe do a little touch up work, also why not get a b16 head? figure you prolly already have this one or running it for a certain class, but the b16 head is better flowing stock,

someone correct me if im wrong.

also what type of build do you plan on doing?
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Old 10-31-2009, 12:40 AM   #3
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Default Re: Building a P8R head

From what I have gatherd, the P8r head flows on par with the B16/gsr. The reason why I chose this head,...besides it rarity, is to test the limits of the particual head( I am pretty sure there is already somone else out there with an all motor built non vtec) and to show a bunch of peeps in my neck of the woods the power of the B20z/P8r combo. LOL this will be my second all out build, and probably my last. (first one was buddys B20vtec)But I plan to go all motor, I know a little, but, it just confused me on the parts I want to get...vtec? non vtec? hope I am not too confusing...
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Old 11-01-2009, 01:34 PM   #4
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Default Re: Building a P8R head

Bump
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Old 11-01-2009, 01:41 PM   #5
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Default Re: Building a P8R head

Need to talk to "Frankacura" he seems to know quite a bit about those heads.
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Old 11-01-2009, 02:39 PM   #6
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Default Re: Building a P8R head

who else runs a P8R here?
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Old 11-10-2009, 12:27 AM   #7
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Default Re: Building a P8R head

BUmp
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Old 11-10-2009, 04:58 AM   #8
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Default Re: Building a P8R head

I've got one as well. I'm in for more info.
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Old 11-11-2009, 10:47 AM   #9
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Default Re: Building a P8R head

Quote:
Originally Posted by namewasdallas View Post
i belive so, you will have to degree the cams in as well, not 100% sure but i think so, I would just drop the head off at a local machine shop, and have them assemble it and maybe do a little touch up work, also why not get a b16 head? figure you prolly already have this one or running it for a certain class, but the b16 head is better flowing stock,

someone correct me if im wrong.

also what type of build do you plan on doing?
im oing a similar build as this guy th p8r head actualy flows quite good its the cams that are laking. im doing a custom grind from bisi to gain th max cfm out of the head but i think building this head is a fine idea for aroun 200 hp or a little more all motor if your goals ar higher then id move to a vtec head. im looking for a nice boostable motor on a budget som im going with this head. good luck
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Old 11-11-2009, 04:33 PM   #10
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Default Re: Building a P8R head

yea, that would be my goal of around 170-200 hp. I just want passing power on demand. I feel 250+ is a little too much on a DD. Just something with boot.

^ I check out Bisi, and man, he get pricey...
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Old 11-11-2009, 05:02 PM   #11
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Default Re: Building a P8R head

I believe while the valves are the same size as the vtec heads the stems are not. So you'll use the B18a/b seals. You'll know when you take it all apart. I have one of these heads also and wanted to build a 85x95 HC H1 engine with it. But I won't do that until I sell my brand new B20VTEC build that Jim Justice built for me.
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Old 11-11-2009, 11:56 PM   #12
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Default Re: Building a P8R head

yeah, I wish I got pictures, but I took it all apart: valves(in., ex.,) springs, retainers, retainers, and keepers. I can see they are very different. I also picked up my buddys P75 head, and took that all apart. I needed the keepers, I have seemed to have misplaced mine. I was planning to use his valve springs, and exhaust valves. His valves didn't look to0 dirty, and the exhaust valve sizes are the same. I can't find a thing about valve lapping on here.
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Old 11-23-2009, 09:05 AM   #13
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Default Re: Building a P8R head

Quote:
Originally Posted by SMSP View Post
I believe while the valves are the same size as the vtec heads the stems are not. So you'll use the B18a/b seals. You'll know when you take it all apart. I have one of these heads also and wanted to build a 85x95 HC H1 engine with it. But I won't do that until I sell my brand new B20VTEC build that Jim Justice built for me.
He is correct.

I don't remember the measurement from Crower but VTEC and non-VTEC are 0.5mm difference in valve stem diameter ( I believe is 5.5mm and 6mm). They are DIFFERENT.

However, you can buy aftermarket parts for LS head, they are exactly the same ( Valvespring, Retainer, Guide & Seal).

The damn thing is aftermarket manufacturers never make 33mm valves for the head which is sad =( and I don't know where I can get the NEW OEM valves.
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Old 11-24-2009, 07:21 PM   #14
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Default Re: Building a P8R head

When I took my head to the shop in my area, Headwerks, he kept saying that it was a B20a, which is the old 88-91 prelude motor. LOL I kept telling him that it was not, but he insited he knew what he was talking about. I had two bent intake valves and my guessing is that he replaced those with the ones from a b20a saying the valve were the same 33mm dish..I now wonder....doing reserch on the WWW.
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Old 02-08-2010, 04:27 PM   #15
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Default Re: Building a P8R head

http://honda-tech.com/showthread.php?t=2709206
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Old 11-23-2011, 01:03 PM   #16
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Default Re: Building a P8R head

i too have a p8r head but on my ls.
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Old 11-23-2011, 08:05 PM   #17
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Default Re: Building a P8R head

Op are you on mnhondas? And if you ever want to sell the p8r head let me know I will buy it, I live like 25 min away from stp
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Old 11-23-2011, 09:28 PM   #18
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Default Re: Building a P8R head

they use the same seals as non vtec. also the intake valves are the same as the b20 engine that came in 3rd gen preludes fyi.
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Old 12-17-2011, 11:51 AM   #19
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Default Re: Building a P8R head

Anymore info? I'm still researching for now till I find definite parts. I'm shooting for 180-200hp.
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Old 12-17-2011, 12:44 PM   #20
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Default Re: Building a P8R head

I built a p8r head for myself earlier this fall. If you need to replace an intake valve you can use the b20a ones (88-91 prelude). everything else, except for the head casting itself, is interchangeable with the p75 head. No need to degree cams or anything.



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Old 12-17-2011, 03:34 PM   #21
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Default Re: Building a P8R head

Quote:
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From what I have gatherd, the P8r head flows on par with the B16/gsr. The reason why I chose this head,...besides it rarity, is to test the limits of the particual head( I am pretty sure there is already somone else out there with an all motor built non vtec) and to show a bunch of peeps in my neck of the woods the power of the B20z/P8r combo. LOL this will be my second all out build, and probably my last. (first one was buddys B20vtec)But I plan to go all motor, I know a little, but, it just confused me on the parts I want to get...vtec? non vtec? hope I am not too confusing...
This is not true at all. The P8R head does flow better that the P75 and PR4 head for sure but not near what a PR3 or P72 can. The P8R ports are the same size as the P75, the difference is the intake cam is a little better and the intake valves are Vtec sized on the P8R. It still has the crappy rocker arm design that is known to throw rockers if over reved, tiny ports and no Vtec. The big thing that makes a Vtec head flow better is the larger intake and exhaust ports, Vtec aside.
The best way to get the parts you need for the P8R head is to order them via the VIN number of the CRV it came out. Being that The B20Z with the P8R head was only made right at the end of the 2001 model year it is hard to find parts by just looking up a 2001 CRV.
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Old 12-17-2011, 03:41 PM   #22
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Default Re: Building a P8R head

Intake cam was exactly the same as the p75 one. I can verify that the ports are the same size as well, I measured both and was a little disappointed since I kept reading that the p8r had 2mm more width on the intake side. Any extra flow is going to come solely from the larger valves.
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Old 12-17-2011, 03:47 PM   #23
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Default Re: Building a P8R head

I know that the P8R has a better cam, maybe it was the exhaust cam. Pretty sure it was the intake came though. Anyways just got Vtec after all the money spent you will be disappointed in the gain from a P8R. A stock B16 head is 30whp bolt on you would get maybe 5-8whp out of the P8R. Now lets put cams and valve train in both heads the Vtec head will put the non Vtec head to shame.
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Old 12-17-2011, 05:34 PM   #24
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Default Re: Building a P8R head

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I know that the P8R has a better cam, maybe it was the exhaust cam. Pretty sure it was the intake came though. Anyways just got Vtec after all the money spent you will be disappointed in the gain from a P8R. A stock B16 head is 30whp bolt on you would get maybe 5-8whp out of the P8R. Now lets put cams and valve train in both heads the Vtec head will put the non Vtec head to shame.


The B20b P8R cams are the worst of the non vtec cams. LS cams and B20z cams would be the ones to swap to. Theres plenty of P2V clearance using the P8R head as well.

yes, the vtec head will increase HP, bit you'll lose torque. Horsepower is a made up number. Its based on engine speed and torque. Ive had better torque #'s with my P8R then with vtec conversions.

Adding cams and valvetrain will help a little, but the stock pistons dont have the compression needed to make the cams come alive. This is a common mis-conception in the honda community.

read up on this post for more P8R info
http://honda-tech.com/showthread.php?t=1467903
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Old 12-18-2011, 07:23 AM   #25
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Default Re: Building a P8R head

I lost no tq when I did my Vtec head. Now the change from a LS intake mani to the B16 intake mani saw a loose of 2lbtf not a big deal. However tq was gained in the top end.
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