Rocker ratio change and spring requirements
Posted: Thu Jun 20, 2019 7:24 pm
Going from a 1.5 to 1.6 rocker ratio change and wondering how that change affects the spring requirements for the same cam?
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Rocker ratio change and spring requirements
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Re: Rocker ratio change and spring requirements
Posted: Thu Jun 20, 2019 7:47 pm
Do you have clearance (coil bind, retainer-to-seal, rocker to retainer, etc)?
Re: Rocker ratio change and spring requirements
Posted: Fri Jun 21, 2019 10:27 pm
No all of that is fine. Just wondering if the increase in rocker ratio places increase load on the valve spring and how to allow for that if that is the case.
I suspect my current valve springs are on the way out so would rather get the right valve springs to suit the 1.6 rockers
Re: Rocker ratio change and spring requirements
Posted: Tue Jun 25, 2019 4:04 pm
That's a multi-variable regression analysis. It involves cam intensity, valve and retainer weight, RPM range and a few other details like these.hysteric wrote: ↑Thu Jun 20, 2019 7:24 pm Going from a 1.5 to 1.6 rocker ratio change and wondering how that change affects the spring requirements for the same cam? . . . . Just wondering if the increase in rocker ratio places increase load on the valve spring and how to allow for that if that is the case. . . . . I suspect my current valve springs are on the way out so would rather get the right valve springs to suit the 1.6 rockers
Short answer, yes, you'll most likely need more spring to control more intensity and more lift.
Re: Rocker ratio change and spring requirements
Posted: Wed Jun 26, 2019 12:01 am
Sounds complicated 
Do people have a general rule of thumb or guidelines? Or is it a case of run it and see and if it doesn't like it run more spring pressure.
Surely people have encountered issues when going to a larger rocker ratio?
Do people have a general rule of thumb or guidelines? Or is it a case of run it and see and if it doesn't like it run more spring pressure.
Surely people have encountered issues when going to a larger rocker ratio?
Re: Rocker ratio change and spring requirements
Posted: Wed Jun 26, 2019 1:06 am
Pro-rata the resulting valve lift or intensity change w.r.t valve motion which will be approx the rocker ratio then add some more 
Re: Rocker ratio change and spring requirements
Posted: Wed Jun 26, 2019 5:12 am
Going from 1.5 to 1.6 increases spring tension over the nose by about 10%. So if you have 300#s over the nose with 1.5, it will be 330#s with 1.6.
If the seat tension is adequate for 1.6, & no problem with coil bind with the added 10% lift, current springs are probably ok.
If the seat tension is adequate for 1.6, & no problem with coil bind with the added 10% lift, current springs are probably ok.
Re: Rocker ratio change and spring requirements
Posted: Wed Jun 26, 2019 8:26 am
Increase the seat pressure by 8-10%, and the max lift pressure by 7%
Re: Rocker ratio change and spring requirements
Posted: Wed Jun 26, 2019 5:49 pm