oversize valves?

[dunkyfried]

What, if any, benefits are there to 1mm oversizes valves in a 1g head ? This will be on a DD 2g w/ 6bolt, t3/t4 50trim, 264s, dsm linkv2, and all supporting mods. Looking to have some head work done and trying to find out the pros and cons.


thanks

 

[dunkyfried]

Will the engine lose HP on the lower rpm side b/c of decresed velocity? I understand the whoel bigger whole more air but will it be falling on its face until higher rpms? I dont want this to have to be a rev happy monster to make power.

 

[ballagsx]

i started a thread with the same question, no one gave me an answere.
after doing some research i found out that the average machine shop charges about $35 to do the oversize grinding on the valve seat, that price is for 8 seats.
i couldnt find anything about performance benifits though, so i also would be intrested to hear what the gains would be.

 

[Nautica985]

Well, I have a ported head with 1mm os valves and with no other mods besides a k@n filter I was able to beat a WRX and I only had 10 psi of air in one of my tires. I think WRXs come with 240hp? so it does give you a decent increase in power. The bad part is that i think the bigger valves and ported head killed my gas mileage. I only get 14mpg if im lucky. I have done just about everything else to correct my mileage and none of it helped.

 

[dunkyfried]

if you search under oversized valves there is alot of threads to look thru but you have to piece together the info... looks like the intake/exhaust sides if done, are pretty much for race applications where street cars can get away with just the intake's side seeing some gains higher up (10-20hp) with no ill affects to the lower rpms..... I would still like to know if both intake and exhaust side are set up with 1 or 2 mm valves with full porting on the mods above would be streetable.. I know I know anything is driveable on the street but look for functionality not just blowing money and only able to use it above 5500 rpms.


damn 10psi in your tire and your racing..do gas stations near you have air pumps.... not being funny cause I know some places dont.

 

[92awddsm]

I have 1mm os intake and exhaust valves and a ported head and it works fine. Cant give any comparison between this and stock because I had my engine rebuilt and changed turbo and several other things at one time. I make full boost at about 2900-3000 rpm and I shift at about 7-7200 rpm. Low end torque is non existent with a 4g63t anyway, so why worry about it? I drive mine daily and have no problems and I dont have to spin the piss out of it. I am also running a b16g, ported, not clipped. The only reason I went with os valves was I plan to get the car into the low 11 sec range later and all my valves were bent anyways.

 

[dunkyfried]

nice ...thanks

 

[TURFNNSURF]

Last yr at the track my car ran 15.32@87mph in the 1/4 with only a K&N filter and MBC @ 16psi on a Big16G ported not clipped. Shortly after that i melted a valve and had the Head rebuilt and ported with 1mm OS stainless steel valves, titainium springs and retainers and 5Speed cams. One week after getting the car back, i returned to the track, ran 12psi on the same turbo, with the rebuilt head and ran 14.35@96mph. I would say that the increased air flow thru the head and valves was the sole reason i ran almost 1 second faster at 4 psi less boost.

 

[Stealth_Racing]

Friends don't let friends drive stock.... hihihi







.....sorry , cool sig