too much cam
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Freshman User
Joined: Jan 2004
Posts: 49
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From: north east mississippi
too much cam
has anyone ever tried to decrease valve lift by changing rocker ratio. i have a roller cam with .714 and .737 lift.i know it is too much for sunday driver,but i still want to try it. would i be better off to re-grind it milder,like .660 .680... also i am running tunnel ram,improved p i heads. looks like valve spring life would too short for light street use. any thoughts on this?
Posting Guru
Joined: Apr 2000
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From: Pryor
You can do that, but you have to realize that you would be decreasing your lift and overall area under the curve thereby hurting performance while not really gaining any of the benefits of a smaller cam. I assume this is a roller cam?? You could increase your lash a bit. This would both decrease the overall lift as well as the duration. Of course by doing this you would likely increase noise and run a greater risk of bending a pushrod. I've never done this personally, but I have heard of people running their cams a little loose or a little tight just to tweak the performance a little.
FTE *******
Joined: Jan 2004
Posts: 791
Likes: 1
From: Pittsburgh, PA
I Agree, you would decrease the lift and duration, but keep the lobe sep centerline as is. This would make for a bit less overlap, but this is still in theory, as a custom rocker would need to made. Then you would shift the rocker tip back from the center of the valve to its trailing edge and cause more valve stability issues. The rocker ratio is better left as it was designed, so that it applies as close to a centered force on the valve as you can hope for. I would suggest having it reground to meet your needs or move on to a cam that is withen your requirements and just sale that one. I think you will much more satisfied, not to mention you would have to spend money to get the custom made ratio rockers and you would sacrifice valve stability and increase valve train wear by upseting the intended geometry.
Elder User
Joined: Jan 2004
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Cam swap. Since you can re-use roller lifters (unlike flat-tappet lifters) you can do the swap for the cost of the cam and gaskets. It's probably about the same (or possibly less than) buying a new set of rockers.
brad
brad
Elder User
Joined: Jan 2000
Posts: 966
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From: Crooked River Ranch, OR
It's not only the lift of the lobe but more important it's the extremely high valve spring pressure and the roller lifters were never designed for extended mileage. You might get lucky and get 20K miles on a solid-roller-lifter engine, while a hydraulic cam or hydraulic-roller cam often sees over 100K miles with no problems.
If you feel you just have to keep the solid-roller, then remove and inspect the lifters every year (usually it's the rollers and needle-bearings that fail) and plan on changing the lifters and springs every two years as a minimum.
Deen
If you feel you just have to keep the solid-roller, then remove and inspect the lifters every year (usually it's the rollers and needle-bearings that fail) and plan on changing the lifters and springs every two years as a minimum.
Deen
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