Just a little tidbit I posted on another website when someone asked about lobe seperation... Thought some folks here might be able to use the info as well...
In a nutshell...
Decreasing lobe seperation:
1. narrows the powerband
2. moves the powerband lower
3. makes the idle choppier
4. makes more power
5. pumps up the midrange
Increasing lobe seperation
1. widens powerband
2. makes the idle smoother
3. takes away from the midrange
4. produces less maximum power
Racers usually use tight lobe seperations. The only exceptions are Pro-Stock, where 500+ ci are revved to the moon with cams so HUGE, tight LSA's produce too much overlap, and nitrous/blower/turbo applications where overlap sends all that extra fuel mixture out the tailpipe!
Tight lobe seperations increase overlap and can help increase velocity in overly huge intake ports (4bbl 351C). This will pump up the midrange, and make the engine feel less "lazy". Some 351C drag race cams have lobe seperations as low as 102-104 degrees. Automatics generally need a tighter lobe seperation for extra midrange.
Small engines with big ports LOVE tight lobe seperations, as do engines limited to smaller sized carbs and/or intakes.
A tighter lobe seperation also allows you to use a slightly larger cam in a lower rpm range. If you want maximum valve timing without revving the engine to the moon, a tighter lobe seperation can make it happen.
Good Luck!
_________________
Mike Burch, 66 mustang real street
302 4-speed 289 heads, 10.63 @ 129.3
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
http://www.fortunecity.com/silverstone/healey/367
<font size=-1>[ This Message was edited by: n2omike on 6/24/04 11:09pm ]</font>