hybrid_vtec

I have had a P8R B20 head for awhile, but I have not been able to run across a B20 block. Therefore, I want to find a way to put it on my B18 block. The problem I run into is the P8R head has an 84mm combustion chamber compared to the 81mm bore of the b18 block. To avoid problems I need to make the combustion chamber of the P8R head smaller. What I was thinking, is to weld up the chamber to make it smaller, and then mill it a little bit(.03 - .04"). Does anyone think this will work? Do any of you have a better suggestion?

Most of you are wondering, why do I want to use a B20 head. And what a P8R head is. The P8R head is a rare B20 head that was only manufactured in '97, and used on the 98 model Honda Orthia. It has 33mm intake valves, and flows similar numbers to the B16 head. Dont believe me! There is a thread comparing the PR4 LS head, the P8R B20 head, and the PR3 B16 head. The flow test concluded that the PR4 head flowed 197 cfm, the P8R head flowed 226 cfm, and the PR3 head flowed 234 cfm. All tests were done at 28" and .450" of lift.

I feel after a little head work and a good valve job, the P8R head could be very beneficial to my setup. Right now I am using a PR4 head that only has a very mild port job and a competition 3-angle valve job. I say the port is mild, b/c all I did was smooth everything out and remove the casting seems in the ports on both the exhaust and intake side. Even with only this, I was still able to produce 172 whp and 136 wtq with my N/A LS setup. It is time to step up the game and see what a well ported and machined P8R head can do for my setup.


For those that hate to read, here are my questions.

What can I do to make a P8R head with 84mm combustion chambers work on an 81mm B18 block?

Could I weld up the combustion chamber and mill it some to help reduce the size?

Any suggestions or thoughts?


Modified by hybrid_vtec at 6:21 PM 12/17/2005

hybrid_vtec

Just so you guys can become familiar with the head I am speaking of:


Here is a pic of the bottom of the head. Notice the stamp at the bottom, P8R.


Here is a pic fom the intake side, notice the stamp again as well.


Here is the date stamp on the block indicating it was made in 1997. It is said to have only come on the 98 model Honda Orthia deeming why it is so rare!


Now for the good stuff!

Here is a 31mm LS Intake Valve compared to the P8R intake valves.


Here is an ITR intake valve from the set that I have laying around compared to the P8R intake valve. Looks like 33mm to me!

projectTeG

passing through

Sam92Teg

Wish I knew some answers for you Hybrid, I am always following your progress with the Non-VTEC B18A/B engines. I mean, your setup got 170 whp, that's better than stock GSR's and has a broader torque curve.

That head might flow so well that some 405's could be in your future, and then you might break the 200 whp mark, good luck. I bet there are some guys here that could tell you exaclty what type of machining you need to run that head.

hybrid_vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sam92Teg &raquo;</TD></TR><TR><TD CLASS="quote">Wish I knew some answers for you Hybrid, I am always following your progress with the Non-VTEC B18A/B engines. I mean, your setup got 170 whp, that's better than stock GSR's and has a broader torque curve.

That head might flow so well that some 405's could be in your future, and then you might break the 200 whp mark, good luck. I bet there are some guys here that could tell you exaclty what type of machining you need to run that head. </TD></TR></TABLE>

200 is probably pushing it, but we will see. As far as running 405's, I may end up getting some and testing them out. I may even try out the Crane #20's. However, I need to find out if I can make this head able to run on an 81mm bore.

projectTeG

i heard something about DonF making like 230whp in a N/a ls. but im not sure maybe he can chime in

GUILOTINE

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_vtec &raquo;</TD></TR><TR><TD CLASS="quote">The P8R head is a rare B20 head that was only manufactured in '97, and used on the 98 model Honda Orthia. It has 33mm intake valves, and flows similar numbers to the B16 head. </TD></TR></TABLE>
Rick is this the '98 JDM B20 engine that pushes like 142whp? Need to know because I picked up a B20 w/ a P8R head that is stamped '97 as well. I
know it has P3F pistons so I was bummed thinking it was 125hp B20 but I think it might be ok.

hybrid_vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by projectTeG &raquo;</TD></TR><TR><TD CLASS="quote">i heard something about DonF making like 230whp in a N/a ls. but im not sure maybe he can chime in</TD></TR></TABLE>

Yes I have talked to Don F before, and he told me about the 230 whp NA LS and a 270 whp NA LS w/ ITB's. These ratings were at the flywheel though. He never explained the setups to me, but I have been curious as to how they pushed out that much power.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GUILOTINE &raquo;</TD></TR><TR><TD CLASS="quote">
Rick is this the '98 JDM B20 engine that pushes like 142whp? Need to know because I picked up a B20 w/ a P8R head that is stamped '97 as well. I
know it has P3F pistons so I was bummed thinking it was 125hp B20 but I think it might be ok.</TD></TR></TABLE>

Yes, that is the motor. I am not sure what the factory rating is for horsepower and torque, but try doing a google search on the Honda Orthia. If I find something I will email you.

The P8R head is definitely a nice improvement over the standard LS/B20 heads(PR4 + P75). This is why I am trying to find a way to use it on my LS. I wish some people would chime in to answer my question and lend some names of a machine shop that could do it.

non-VTEC

why not find a cheap B18A/B and have it re-sleeved to 84mm.......?

yes its allot of money but it will save you downtime and you know that it will make good reliable power....

i don't think you can run that head on a 81mm bore block.......you will go through head-gaskets pretty quick.

hybrid_vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by non-VTEC &raquo;</TD></TR><TR><TD CLASS="quote">why not find a cheap B18A/B and have it re-sleeved to 84mm.......?

yes its allot of money but it will save you downtime and you know that it will make good reliable power....

i don't think you can run that head on a 81mm bore block.......you will go through head-gaskets pretty quick.</TD></TR></TABLE>


I know, but did you read my first post?

I am wondering that if I weld up the chamber and mill it down a lil, could I get it down to where it will fit right?

I do not have the money for a sleeved block right now. Once I get back to the east coast and do not have to pay an ***-raping amount of bills, I will have plenty of money again.

GUILOTINE

Hey Rick I know of a real good machine shop here in the East county that can weld up the cumbustion chambers and do a full radius valve job on a serdi for you. Send me an e-mail or call me if your interested.

hybrid_vtec

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GUILOTINE &raquo;</TD></TR><TR><TD CLASS="quote">Hey Rick I know of a real good machine shop here in the East county that can weld up the cumbustion chambers and do a full radius valve job on a serdi for you. Send me an e-mail or call me if your interested.</TD></TR></TABLE>

Thanks Gil. First, I want to make sure this can be ran with these modifications to the head and without any issues.

flyrod

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybrid_vtec &raquo;</TD></TR><TR><TD CLASS="quote">
What can I do to make a P8R head with 84mm combustion chambers work on an 81mm B18 block?

Could I weld up the combustion chamber and mill it some to help reduce the size?

Any suggestions or thoughts?
</TD></TR></TABLE>

Well, if you plan on using the head on 81mm bore indefinitely, then you can modify the head. If you think you will end up going with a larger bore later, then you may not want to modify it. If you want to mod it, you could weld it up, or you could just mill ~0.030" off it to bring the quench pads flush (or nearly so) with the surface of the head. Welding is usually an expensive procedure, while milling is relatively cheap. However, these mods are basically irreversible, so you should make sure it's what you want. Finally, while it may not be ideal, the head will work fine if you just bolt it on.
So, my suggestion would be to mill it if you plan on staying 81, and just bolt it on (use a B20 HG) if you plan on going bigger later.

GUILOTINE

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

Well, if you plan on using the head on 81mm bore indefinitely, then you can modify the head. If you think you will end up going with a larger bore later, then you may not want to modify it. If you want to mod it, you could weld it up, or you could just mill ~0.030" off it to bring the quench pads flush (or nearly so) with the surface of the head. Welding is usually an expensive procedure, while milling is relatively cheap. However, these mods are basically irreversible, so you should make sure it's what you want. Finally, while it may not be ideal, the head will work fine if you just bolt it on.
So, my suggestion would be to mill it if you plan on staying 81, and just bolt it on (use a B20 HG) if you plan on going bigger later.</TD></TR></TABLE>
please explain me how a closed combustion chamber will burt it later?
Ive heard nothing but good things about a closed combustion chambers.

allmotorek8

iTrader: (3)

i was just reading and thinking the same thing i just picked up a 97 b20 head also and was gonna throw it on a stock ls block maybe with pr3 or ctr pistons mircopolish the crank and shootpeed the rods with arp rod bolts then have the b20 head pnp with itr throttle body , obd1 prelude injectors, msd 2 step with launch control, dc 4-1 header , cold air intake, 2.25 inch pipping with itr muffler ,tuned on chrome.

so what is the advantage of the b20 head on a ls block vs ls head on ls block?

Fkned

The one problem is that to weld up the entire chamber to 81mm I'd think that you would get to close to the seats with the welding and have to replace the seats.Welding that much requires alot of heat right on the edges of the int valve seats.

h22crxpwr

how about instead of welding and modifying the head you spend that money on a B20 block. the amount you will pay to weld up that head and the potential damage you could do to it is not worth it. B20 blocks are pretty affordable..

IanB

Agreed, it would likely be cheaper to have oversized valves put in a P75 head anyways.

JCushing

mill the head so the quench area is flat, there goes your 84mm chamber

alejotorres

hi:
i dont know where to post but i need some help.
i need to replace my p8r valves, cause they are so worn.
i need the part number or something that helps me to find this.
thanks

acnup78

Do you use the B20 HG when you mill it or just a B18 HG