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LT1 Aluminum Rocker Arms And 58mm Throttle Body Upgrade - Top End

Part III: A Little Elbow Grease And A Few More Bolt-Ons Help Free Up More Power On Our 355 LT1

0902gmhtp_01_z Lt1_aluminum_rocker_arms_and_58mm_throttle_body_upgrade Working_on_rocker_arms 2/19

In our last installment, you may recall RaceKrafters swapped out the refurbished stock LT1 heads and small Comp Cams bumpstick for the Edelbrock Performer LT1 heads and cam package. At which point, we retested the Edelbrock Air-Gap intake manifold and 52mm throttle body, which got us to a grand total of 393 horsepower and 393 lb-ft of torque. But like eating at a French restaurant, this tasty meal didn't come close to satiating our appetites. So for this go-round, we figured we would stop off for a snack before grilling up a big juicy steak in our final installment. Before moving on, we were hell-bent on wringing every ounce out of the current Edelbrock combo, and even comparing a ported Air-Gap intake to a ported stocker.

Before I arrived at the Lancaster, Pennsylvania shop, RaceKrafters went ahead and ported the openings of the intake runners on the Edelbrock heads to better match the gaskets and intake manifold runners. The smoother transition was carried over to the Edelbrock intake as well, and taken all the way up the runners to the plenum-and any excess casting flash was removed. At the same time, RaceKrafters also used its own proprietary methods of prepping a stock LT1 intake, which included porting the runners and smoothing the throttle body opening using a special military-spec filler that is resistant to gasoline and virtually any type of corrosive agent likely to be found in an engine-including methanol. In the interest of eliminating any weak links or cause for doubt, we decided to throw an Edelbrock 58mm throttle body (PN 9310) and Summit Racing 1.5-ratio aluminum roller rockers (PN SUM-G6935-16) into the mix. With an increase in airflow and decrease in valvetrain friction and weight, we were sure to drain the last bit of power left in this combo. Enjoy this snack in anticipation of a big meal to follow.

First, I'd say we can discount the idea that a 58mm throttle body is too large for a stock cube motor. Though its average horsepower suffered a little, its peak was higher and it did not manage to kill the torque like many have suggested. Since these gains would have only increased with a larger cube motor or forced induction, it also gives the motor room to grow. Second, despite the fact that the roller rockers were the stock 1.5 ratio, they still managed to pick up power just through valvetrain dynamics. Never underestimate how much power friction and weight can rob from your motor. Lastly, Edelbrock put in a valiant effort with the LT1 Air-Gap intake manifold, but for a 350 to 355-cube motor it is hard to beat a stock or modified stock intake.



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