Anyone care to shed some light on the discussion of the benefits from oversized valves.. I figure heck I'm spending $175 on valvesprings, maybe I should also get some oversized valves. This head buildup is on a budget, but if it's a definate worthy upgrade I may consider it... Any before afters? TIA


[Modified by teg92, 2:05 AM 12/11/2001]

 

A non vtec head may yield gains from oversize valves since they are
smaller than the dohc vtec valves. dohc vtec valves dont gain much
unless there is a significant displacement increase.

 

Interesting... Well this would be on a nonvtec head... I really can't justify it'd be worth the extra cash unless it can donate at least an extra 5hp next to everything else (valvejob, headwork, cams etc...)

 

Oversized valves allow you to increase the valve seat diameter and then your head will allow more air into the combustion chamber. Basically, better breathing. Why else would racing teams increase valve size?

 

Ok.. Well I obviously figured out that bigger valves = more air... But what I really mean to ask is how much it'll affect things. I don't really hear many people talk about having oversized valves when they do headwork or buildup an engine... Is it cause it's not worth the cash compared to the gains or what?

 

It all depends on what you think is worth it......maybe we should ask portflow what they think about honda's and oversized valves since everyone here suggest to get your headwork done there. I am gonna go email them now.

 

Cool thanks let us (me) know!

 

BUMP.... Jeez a tech website and nobody comments on oversized valves???

 

Rofl, I haven't even gotten answers back in the emails.......I am gonna go bug the guys in Kills!!

 

Got an email back from portflow.....
"the stock sizes work well with the 1.6 and 1.8 liter engines"

So, nope, no need to upgrade the valves.

 

wierd... Cool.. now I just need to decide whether or not I am gonna go for a massive torque bump in midrange (4-2-1 stepped & ported LS IM) or all highend (4-1, 2.5" collector & ITR IM modded to fit LS) setup for my LS... Opinions??

 

Um, each and every head combination is different. I.E. asking about a honda B series head.

 

Just a quick search and the biggest valves I could find for a b16 were 1mm larger than stock (34mm intake/29mm exhaust). Doesn't seem like there'd be room in a 4 valve head for anything much bigger.

I'd guess that bigger valves would be the very last thing you'd do on a b16 head, after you had it ported, deshrouded, extrude honed, or whatever. Probably improved valve design, with thinner stems and better flowing rims, would gain as much as the increase in size.

 

Some top bay area builders swear by the stock valves.. Oversized valves were explained as not being worth the extra money..

The biggest horsepower engines are fueled by nitro-methane.. Does that mean u should too?

 

yeah i know im a lil late on this.... but right now the builder in so cal that everyone in the all motor class has had their block done at [RS MACHINE WORKS], but as for head work i would have to say portflow does some pretty good work, but personally i still stuck with RS, and my car is running stronger than anything, and since you are running a straight up LS, i think you should talk to RS cause they built the fastest LS all motor to date... no VTEC components or anything.... either search around for taren king [the driver] or just straight up RS motorworks [their old name] aiight.... just trying to help out... peace

Jason P