I have a full ferrra valve train in my car with valves .05 oversized and i want to get some cams. I hear that you are not supposed to put aggresive cams with oversized valves but i also hear that you can i want to add Skunk2 stage 2 cams is it possible does it need modification or can it work with what i have.

 

I cant speak for myself, but I have been told by people smarter than me i.e. Omni that the optimal flow can be achieved with standard sized valves. the valve timing makes alot of power on these heads. the pocket gets REAL CLOSE... especially if you mill the head; if you have less than .020" clicking clearance between the valves at overlap with a nice cam and then add 1mm of valve size between them, it really limits your choices of cams. ***post correction below*** in this case, since making any kind of power in these motors is dependent on the right cam choice. why would you limit that choice for a few extra CFM when a head porter can give you back and then some with the right valvejob/cam choice. hope that helps I have never installed s2s2 cams and then locked vtec and seen where the valves hook each other. if you go .5 over and use these cams, I wouldnt TOUCH the cam timing at all, you will have to run a very stiff spring pressure which will cause issues of its own... not to mention dont misshift... all the data IMHO points to standard sized valves. Like it was explained to me it would depend on the purpose for the build. Some racing will only let you use a stock cam, this might be the right case for oversized valves.


Modified by MikeSarr_GSR at 2:18 AM 12/24/2004

 

Thank you but you said add 1mm and mine are .5mm bigger is there a big difference and people have told me since i have put them in almost 35000 miles ago they are pretty well set in and that a aggresive cam will work and they have built many more engiines than i what do you think

 

So i would probably be better off with just ITR cams or CTR right or skunk2 stage 1 etc

 

here is another question why do they make oversized valves what is their correct application if not for all motor?

 

when you have two .5mm oversized valves, do the math. you remove 1mm from the total "clicking" clearance between the valves at overlap. **edit post below** you limit the gains you can make with a cam by reducing the amount you can move the cams in tuning them with gears. not to mention, the choice of cam. my opinion is stay standard sized. i'm done, there are more people here I am sure that will agree or not. if you dont open the throat of the valvejob all you are doing is putting a bigger valve on the same sized seat. its a job that requires you to do head work the get the full benefit of the oversized valves and thats a fact.


Modified by MikeSarr_GSR at 2:17 AM 12/24/2004

 

actually it would still be only .5mm it adds .25mm to each valves circumference on the edge.Just like when you over bore the cylinder by.5mm it isn't added to just one side of the sleeve,.25mm is equally added in every direction.

 

Haha ed is right.

But MikeSarr_Gsr is right too. Skunk 2 specificly says DO NOT USE OVER SIZE VALVES !!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rev limiter &raquo;</TD></TR><TR><TD CLASS="quote">Haha ed is right.

But MikeSarr_Gsr is right too. Skunk 2 specificly says DO NOT USE OVER SIZE VALVES !!!</TD></TR></TABLE>


YUPP...

 

ahhh yess... I mis-spoke. .5mm in 2 directions... .25x2 valves .5mm less clicking clearance... still too much clearance to loose for valve timing issues on a moderate to big cam...


Modified by MikeSarr_GSR at 2:18 AM 12/24/2004