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Old 11-16-2006, 07:19 AM
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I re ran the numbers the morning, checking everything over.
Somehow when I ran the flat tappet yesterday the SCR got changed to 10.6 . Ihave no idea how that happened, but that's what scewed the results.

Tried it again today to see if I could prove myself wrong: Used the same specs at .050, same LSA, same ICL, just changed the type from mild flat tappet to aggresive hyd. roller (which should be maximum benefit) to see what would happen. The roller returned with a little less torque on the bottom end at up to 4000 RPM, but then the roller started to shine 557HP at 6000 RPM versus the flat tappet's 541 HP at 5500RPM (after which Engine analyzer said the lifters were pumped up). At 6000 RPM the flat was only making 483 HP, which is due to lifter pump up - I don't think that is represented correctly, but oh well.

So then, just for fun, I jacked the flat tappet duration until the @ .200" duration was the same and reran it. It got closer to the same peak HP (as expected), but the torque in the lower end was way down, and the idle vacuum would be 9" Hg. So it would be really too hot for the street I think.

Someone suggested I try running the roller with an extra 10 deg. of duration - so I tried that too. Unfortunately, my SCR doesn't support that very well, but I still came up with 565 HP at 6000 RPM, while loosing torque up to 5.5K. Idle vacuum dropped to 9.9 (the flat was 11.8 which suggests more street friendly). Clearly the first roller was better in almost every aspect at this SCR of 9.9.

SO there you have it - the roller reigns supreme if you want to be streetable and have enough cam to make those big heads breathe. Sorry for posting inaccurate data - I should have been paying more attention.

If budget is an issue, the street racer would do the flat tappet and then use the "extra" money for nitrous. Or else build a mild big block 496
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