For forced induction applications I have seen significant increases with skilled porting and over sized valves. Increases are greatest on the exhaust side.

 

So I'm getting Mix review here. Sideway have say he have seen significant increases with skilled porting and over sized valves. Increases are greatest on the exhaust side. Is the significant increases with a fully built motor or you will see some gain on a stock bottomend also?

 

the conclusion is..Slap your stock head back on and dont worry.(or dont touch it if its not off) Put your mind and money to something else.
Put in as much boost as you feel safe with and since you have great Tuner resurces over there,dyno tune it to perfection and enjoy the car...dont give it much tought in any case.It will plenty of fast in any case and i bet you wont feel any difference in power with both scenarios. And this is not F1 where you need every last HP. when you boost enough you wont feel any change from this to that.. its just boost and all you will see is your tires going away.
you have two options,send your head for P&P stick with oem valvetrain or spend 2k on everything aftermarket or option 2 keep everything stock which i would choose.
I would consider this more if you were NA but even than the gains are only felt for a day,than everything feels normal again and its not like you are in somekind of competition so you need every last hp for your AIR and FUEL...
either loose 2-3 weeks(downtime) at best for this or just leave it as it is.
in the end not much difference when you drive the car,you get used to everything...even a great P&P job...
this would be on the table no questions asked if this was a race car....
Either you do it or you dont, but remember,Honda isnt in the carpenter business.So they must know what they are doing and this is their top of the range engine...

 

I was running my head on a stock bottom end for several years. The additional horsepower was significant. Where most Vortech S2000s with 7 psi boost were making 300 rwhp I was seeing 360 rwhp at 6 psi.

 

Is that running with the oversize valves 0.5 IN /1.0 Ext if so I will be set then

 

[QUOTE=Sideways,Apr 29 2008, 10:20 PM] I was running my head on a stock bottom end for several years.

 

Thanks alot for the input

 

There is an optimum valve size for a particular rpm range. A street car, for all intensive purposes, will use the entire rpm range. Honda did a good job, stick with it. What you are proposing can't be cheap, why not put the money to use somewhere else...? Given the record of hp per dollar netted by porting and polishing, especially if you aren't even building the engine or messing with the compression ratio or displacement , I would think that almost any tastefully implemented modification would yield a faster car, per dollar, when compared to labor-intensive headwork. It should also be noted that simply throwing money at a cylinder head shop may not yield gains. It all depends on the skill and experience of the technician. I can think of dozens of better ways to spend the sort of money you're talking about.

For starters, you should probably buy these.
- Four Stroke Performance Tuning by A Graham Bell
- Forced Induction Performance Tuning also by A Graham Bell
($50 for the pair on amazon, best $50 I've ever spent on a car!)

-LRW

 

Not to bore you with the searching i did before i did my head,i found out that the head of the s2000 is good flowing head as it is and various test from portshops saw that there is no yield in performance from bigger valves in this car just that on the best scenario they got 15% better flow on the exhaust with the job and only 0.5 oversize(not 1mm) on the exhaust. I bet with ported and polished exhaust you can get up to 10% better flow(stock valves)..but anything above that for any case scenario is good luck...
In any case to quote Omniman...on a standard Bore honda (s2000 in this case) with bigger valves you would be going 1 step forward in size and than going 2 steps backward with flow. since the valves are so close now.and a 1mm is a tight sqeeze.
If you bore the block 2-3mm with bigger bore pistons than a bigger sized valve is in place, and you can open the head chanmber than,

Not to discurage anyone..but when i was doing my research,and i was ready for the whole bunch,valvesprngs,valves,retainers,(when money is no object) I found out it was not worth it and that OEM was on par with everything.

 

Sorry, but your post sounds like sour grapes to me.

I have seen many boosted S2000s putting out more hp because of a good reworked head with oversized valves.

ABV is over 400 rwhp with a Comptech supercharger and an Alaniz head with oversized valves. Casterdog is over 400 rwhp with a Vortech Supercharger and and Alaniz head with oversized valves. Mine is over 460 rwhp with a Vortech Supercharger, 9.2:1 bottom end and and Alaniz head with oversized valves. These heads have documented increases in flow and perform as such.

I have also seen shops putting out heads that did not increase the flow despite larger valves. They were not ported in an advantageous way. The S2000 head responds to changes different than many other heads and it is easy to see the flow decrease with standard techniques.