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Buick Big-Block Distributors

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1970 GS455 Stage1 Track & Engine Dyno Tests

The graphs in the first sheet below shows the increase in torque and HP that resulted from using solid lifters and heavier springs with the same cam. The spring closed and open pressures were increased to 150 and 350lb, respectively, and the tappet lash was set to 0.004" cold. The relatively simple changes to the lifters and springs resulted in an increase in maximum horsepower from 480HP @ 5100rpm to 540HP @ 5950rpm.

The second sheet records the best Stage 1 run time of 11.749sec @ 114.06mph, which was achieved at the track following the above mods to the valve train. These mods were implemented during series of engine dyno tests. The dyno curves were measured with an acceleration rate of 400rpm per second and corrected for standard temperature and pressure. The photos show the test setup.

Initially the hydraulic lifters had been installed with a preload of 0.050". Evidently the lifters were pumping up and causing the rapid decrease in power after 5100rpm as shown by the black curve in the graph sheet.  With the preload removed to 0.0", the lifters behaved better but the HP still dropped off rapidly after 6000rpm. We tried anti pump up lifters but  these did did not offer any significant improvement. With the solid lifters and heavier springs the engine now revs effortlessly to 6500rpm as shown by the red curve, resulting in 0.5s better track times.

 

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