Lets Talk Rockers
On The Tree
Joined: Sep 2016
Posts: 103
Likes: 18
An old racers trick (in a restricted class) was to purposely run the wrong length pushrods (whether too short, or too long) to gain or lose lift/valve action..........because of the non-linear nature of rockers. Played hell on the valvetrain, but all they cared about was that things lasted long enough to get through a few 1/4 mile passes. And it worked. Well.
No rocker has a linear ratio. This is because the tip of the rocker moves in an arc (with the fulcrum as its center point), while the tip of the valve simply moves up and down vertically. A 1.7 rocker (or whatever said rocker may be) is only 1.7 ratio in a very narrow window (usually around mid-lift and several thou to either side of it). Aftermarket roller tipped rockers gain a few hp (if the actually do, never take magazine articles as gospel) because the ratio is usually a little higher than what's advertised. "1.5" may actually be 1.7. They can get away with that because at some point in the lift curve it is assuredly 1.5. And 1.4. And 1.3. Even the OP's current rockers, the crane "quick lift" rockers gain their "quick lift" by designing the rocker such that the ratio is much higher early in the lift curve, then tapers off quicker towards mid-lift. Using them (and whether or not they will gain anything) depends on whether or not the engine wants a quicker lift curve, as one can easily overshoot the port. It's one of those situations where if the engine gained power, it likely had the wrong cam in the first place. But all rocker ratios, by nature, are non-linear. No 1.7 rocker is 1.7 throughout the entire lift curve.
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
Likes: 442
This is a handy bit of knowledge regarding the quick lift Cranes. The question for me now is, will I lose power going to a factory rocker? After all, the car was tuned with this setup. Assuming that when I pull the valve cover I find that all of the rockers are in good shape, would there be any benefit to swapping back to the factory style? Other than maybe being more reliable?
TECH Fanatic
Joined: Jan 2017
Posts: 1,758
Likes: 442
You're talking about these? http://www.ws6project.com/user_stor/...oducts_id=9356
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The Chinese are saturating the US with knocked-off GM rocker arms which is probably why they fail. https://www.alibaba.com/showroom/gm-rocker-arm.html
Buy GM Performance rocker arms, then add CHE bushings and don't trust anyone offering to sell you GM rocker arms unless it's a GM Dealer like SDPC: https://www.gmperformancemotor.com/category/LS2132.html
Buy GM Performance rocker arms, then add CHE bushings and don't trust anyone offering to sell you GM rocker arms unless it's a GM Dealer like SDPC: https://www.gmperformancemotor.com/category/LS2132.html