Roller rockers

[bison]

If you are talking about the seat to seat duration it does not change, if you are talking about the duration at .050 or the duration at .200 it changes measurably since the valve is getting to those opening points sooner with a higher rocker ratio. Its very simple math once you understand it.
Mike

Exactly and this is why increased rocker ratio can help a lot if there is room for the lift and the valvetrain will remain stable.


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[gunzandgearz]

That is correct and I personally think that its easier to get where im going with the cam being ground assymetrically.Its a lot cheaper having a special ground cam then playing with all the different issues that come with longer rocker ratios such as pushrod length, spring problems, wearing out valve guides because of extreme valve side loading, piston to valve clearance,[especially if engine is already together],and that's not to mention you do all of that and the engine doesn't like it.This is all good if you are looking for every last ounce of power like an nhra pro stock car but not for a daily driver or a car you take to track once in a while in my opinion

 

[turbo89]

Duration increases measurably at higher lobe lifts with increased rocker ratios and decreases measurably with reduced ratios.


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This ... X2 ... whenever possible the higher ratio will help .. its a very noticeable difference

 

[John Wilde]

Guys let's keep these conversations Fast with Class.

 

[gunzandgearz]

I don't care if you measure the valve lift at .020 at .050 or seat to seat [or advertised so your layman ass can understand, get your Chinese degree wheel out of your craftsman box and stick it on the next engine you do and check the at .020 or at .050 btdc measurement and then move the degree wheel around to at .020 or .050 atdc and tell me what the degree wheel tells you. And then install a longer arm[ rocker] just making sure you are keeping up and do the same test, then tell me the numbers you come back with. That's ok ill go ahead and tell you,THE SAME FREAKING NUMBER. THE DURATION WILL NOT CHANGE . The valve will leave the seat or .020 or .050 and will return at the same point. THAT IS THE DURATION AND WILL NOT CHANGE NO MATTER HOW LOUD YOU SCREAM.The term duration is the amount of crank degrees that the valve leaves the starting measuring point and returns to the same measurement point on the backside it will not change no matter what you say or what different rocker you put on it. Now the valve will be farther off the seat at any givin crank degree but that term happens to be called the curtain area and it will be increased, but calling the valve off the farther off the seat at any givin lift point is not more duration.

 

[TurboBuRick]

 

[fastblackracing]

Will someone please take out the garbage that has begun to smell up the joint around here?

 

[John Wilde]

Team, I had to take some administrative action due to how this thread was going.
There aren't many of us left, it is discouraging that we can't share ideas and opinions without name calling.