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Crane roller rockers

This is a discussion on Crane roller rockers within the Internal Engine forums, part of the LSx Technical Help Section category; Do I need to replace my springs and pushrods to install my 1.7 Crane roller rockers and how much horsepower ...

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    candy red
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    Crane roller rockers

    Do I need to replace my springs and pushrods to install my 1.7 Crane roller rockers and how much horsepower is there to gain from the rockers?

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    Member MISFIT's Avatar
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    Quote Originally Posted by CandyRedZ28 View Post
    Do I need to replace my springs and pushrods to install my 1.7 Crane roller rockers and how much horsepower is there to gain from the rockers?


    probly not much, but its always a good idea to beef up the LS1 valvetrain, as it is the LS1's weakest point....


    set of comp 918's to 600 lift and chrome moly pushrods and your set.

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    Since the origional rocker ratio is 1.7:1 just changing the rockers will not effect anything. Better pushrods is allways a good idea if you plan on buzzing the engine. Springs won't hurt either.

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    Grand Imperial Wizard Sarge's Avatar
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    Just a little heads up...NAPA sells the exact same rockers made by the exact same company for a helluva lot less.

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    Mag Red
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    Pushrods, yes definitely. The Crane rockers require a shorter pushrod, 7.25 for a stock setup. Springs, yes. These rockers accelerate the valves much faster and come off the seat at almost 1.8 whereas the stock rockers come off the seat at 1.54. You also need the rest of the kit to make them work, I assume you have the adjusters, studs, guide plates, etc.

    If you go over the Popular Hotrodding, David Vizard has a cam aritcle in the tech section and he explains the advantage of accelerating the valve quickly off the seat along with a lot of other good information. Nice article in that it doesn't favor one company, but rather approaches most things from a technical standpoint.

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    Senior Member mrr23's Avatar
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    Quote Originally Posted by Stinkbug View Post
    Since the origional rocker ratio is 1.7:1 just changing the rockers will not effect anything. Better pushrods is allways a good idea if you plan on buzzing the engine. Springs won't hurt either.
    that depends on what rocker you use. not all rockers are the same. here's a excerpt from the vinci website about how different rockers work

    Install a dial indicator on the retainer and a degree wheel on the crank. Plot a lift vs. degrees of rotation curve. Then install the Crane LS1 1.7 rockers (with the pushrods in the Crane kit) and plot the same curve. Measure the duration at .200" net valve lift. The Crane rockers will definitely provide more duration at this checking point. The reason for this is that, contrary to popular belief, the stock LS1 rockers are only 1.7 ratio above .480" valve lift. They actually start the valve off the seat at a 1.54 ratio. What do you think that ratio does to a "super fast" cam lobe? Slows it down quite a bit? The Crane rockers, properly installed, bring the valve off the seat at 1.79. Doesn’t take a math wiz here to see what combination is going to get open quicker and longer!! If you really want to see something interesting, take two lobes that have identical .050" seat-to-seat timing, identical .200" lifter rise timing, but one provides .583" valve lift with 1.7 ratio and the other providing .551 lift with 1.7 ratio. Plot a lift vs. duration curve with any rocker you want (other than Crane) and measure the duration at .200" valve lift. Then do a plot of the .551 cam with 1.8 Crane rockers (this will net out .583 also) and measure the duration difference at .200" valve lift.

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    silver
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    Oups!

    mrr23,

    You are correct! I forgot the Crane rockers are different at low lift. I have not played with these. This would increase the duration at low lift and make the cam look bigger! Not a bad idea!

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    Senior Member mrr23's Avatar
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    which is why they work so well. i had them on the wife's car. these rockers were banned

    From Crane Cams Newsletter #184

    Crane LS1 Gold Race Rockers “Too Powerful!” for Daytona!

    At this year’s inaugural Grand American Road Racing Series races at Daytona International Speedway, Crane Gold Race rockers used on the LS1 powered Pontiac GTOs were declared illegal for competition because they provided “too much of a power increase!!” On their first runs in practice, the new GTOs (fielded by Spirit of Daytona Racing) were as fast as last season’s series-champion Mustang! That was without any chassis tuning or other “tweaking.” It isn’t good to be that fast “right out of the box” with a totally new vehicle. Series officials decided that in the interest of keeping competition “fair and equal” to all brands, they needed to slow down the new GTOs. They evidently had heard “rumors” that Crane’s “Quick-Lift” rocker arm geometry provided a significant horsepower advantage (14 - 15 hp at the rear wheels) over the stock rockers even with the same 1.7 rocker ratio. As a result, they declared the use of aftermarket rockers “unacceptable” and mandated the use of stock rocker arms for use in the Grand Sport Series.

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