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Crane #133052

September 1 2013 at 6:15 PM

George Pence  (Login gpence)
A1
from IP address 108.218.153.39


Response to Re: It's small enough to work well for those gears and a slushbox

The timing figures based on maximum lift indicate this camshaft is utilizing asymmetric lobes. The LSA is 112°, which in a street motor with big valve 4V heads shall perform similarly to a camshaft with 108° LSA in an in-line valve motor. That's the Crane 284 H12 grind, part number 133052. This is not a bad cam, in fact its quite a hot performer.

60° of overlap is OK, its about the max I recommend if low rpm performance is a concern. Overlap based on the 0.050" duration figures is about 4° (hydraulic intensity is 56°), this is further indication you wouldn't want more overlap with these lobes in a street engine.

The intake valve is closing at 41° ABDC (measured at 0.050") which is one degree more than some engine guys recommend for a street Cleveland in order to avoid reversion, not the end of the world. The relatively late closing of the intake valve will also take a bite out of the motor's dynamic compression. The exhaust valve is opening at 75° BBDC, which is a little late for my preferences. So to avoid reversion, raise dynamic compression, and to open the exhaust valve sooner I'd run this cam about 4° advanced.

Four degrees advanced would look like this:

284°/284° advertised duration
112° lobe separation angle
Int lobe mathematic centerline = 107° ATDC
Ex lobe mathematic centerline = 117° BTDC
----------------------------------------------
Exhaust valve opening = 79° BBDC
Intake valve opening = 35° BTDC
60° overlap
Exhaust valve closing = 25° ATDC
Intake valve closing = 69° ABDC

Notice my lobe centers are based on the mathematical centerline of the lobes, not the point of highest lift. The overlap event is not centered around TDC, but that's something we gotta live with when we select a single pattern cam.

-G
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This message has been edited by gpence from IP address 108.218.153.39 on Sep 1, 2013 6:17 PM


 
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