The teg will be out in a few months and its time to make some adjustments on the engine!
What do you need to do to fit a P8R head on a 81.5mm b18b?
I have the block already, rebuilt 81.5mm oem spec, ran it last summer with a p75 head untouched and crane 0012 cams (stage 1) and a street tune, everything else bone stock no cam gears, 14.3@96 mph in a DA ls. I am very interested by the P8R head and I have not seen anybody run it on a b18 block.

Can the head be milled enough to reduce the combustion chamber size from 84mm to 81.5mm?
If so, how much approximately and what will that do? will it raise compression, be prone to head gasket failure, will the valves (vtec size) stick out too much and hit the pistons if they are not notched?
I'm guessing I will need adj cam gears to degree the motor, which I was planning on doing anyway.
thanks for all the answers!

 

What you say "OEM spec", do you mean B18B pistons also?

 

yes, all oem block, just not standard size.

 

Are you suggesting milling the head to get the lost compression due to the larger combustion chamber of the P8R? I would think you would be better off to weld the combustion chamber on the P8R then machine...not worth it IMO...I can weld it, and machine it myself and I still wouldn't do it for myself (not worth all the work for the small performance gain)

 

I was thinking about milling the head to reduce the diameter of the combustion chambers from 84mm to 81.5mm. I agree that its not worth it performance wise if you have to weld and machine, but it would be fun and unique though. I'm a student so budget is tight, I can get a p8r head for 60$, if I can just mill it simply to make it work it would be worth it.

Unless someone tells me that you can run a untouched 84mm p8r on a b18b block and there wont be a problem but to me it doesnt sound like the right thing to do.

 

milling the head will not reduce it from 84 to 81.5mm. Its just going to reduce the CC's of the chamber

 

An untouched P8R head will work fine. Just don't use cams that are really big.

 

thank you for you responses. I tought since the b20 block was 84mm, the head was too and it would not work with the ls 81mm unless you shave it (read that in the p8r thread years ago). Why not use large cams? because of possible p2v contact that wouldnt happen with the 84mm block?

 

You could possibly have piston to valve contact, you never know until you clay the engine.

 

yes! claying and degreeing can be overlooked but its so important when building a cammed engine.