Quote:
Originally Posted by madmaxx
I called Roush prior to buying mine and asked why the numbers differed so much on the dyno sheets and why they were not all the same. They replied depending on air temp, humidity etc there will be a variance. This is the first I have heard of a 434R, I wonder if they are all 434R but they now call them 427's because 427's is a notorious number. Either way I am thrilled with mine.
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You may have percieved that particular explanation of power values from Roush or a dealer of their product however the dyno sheet can express both corrected power values and as tested values. When using the corrected values it's comparing apples to apples regardless of test conditions. Here's a dyno correction calculator for reference.
http://wahiduddin.net/calc/calc_cf.htm
Some of the reason the corrected numbers vary from assorted engines is because they're set up diffrently. Single plane intake manifolds make the most power. Dual plane intake make less. Cam specs may vary from one Roush engine to another even if they're both 427Rs. They don't seem to want to discolse cam specs. Timing is another reason why the engine power values vary. Roush is pretty tight with detail I'm sure. If they put together two alike engines with the same tune they'll probably make really close power.