raycow said:
its the operational range, take the larger number in front of it subtract the lower number and you get the rpm range
190-200-- 700-4200(3500)
200-210--1000-4750(3750)
210-220--1200-5200(4000)
220-230--1700-5700(4000)
230-240--2500-6500(4000)
240-250--3000-7200(4200)
250-260--3500-7800(4300)
40-50 CI/cylinder (320-400cid)
duration rpm range
190-200-- 500-4000(3500)
200-210-- 800-4000(3700)
210-220--1000-5000(4000)
220-230--1400-5500(4100)
230-240--2000-6100(4100)
240-250--2500-6700(4200)
250-260--3000-7300(4300)
50-60 CI/cylinder (400-480cid)
duration rpm range
190-200-- 500-3750(3300)
200-210-- 600-4250(3650)
210-220-- 750-4700(3900)
220-230--1000-5200(4200)
230-240--1500-5700(4200)
240-250--2000-6200(4200)
250-260--2500-6800(4300)
EXAMPLE
if you took the last line above 6800-2500=(4300) represents the total intended operational range
(or put a different way the cam will become efficient at about 2500rpm and loose efficiency at about 6800rpm)
keep in mind that power band stated is an estimate, and assumes the rest of the engines components, like the headers and intake manifold,cylinder head port size, carb size,etc. and the compression ratio match the intended power band, a chart like this may help
http://garage.grumpysperformance.co...uild-the-engine-to-match-the-cam-specs.11764/
http://garage.grumpysperformance.com/index.php?threads/semi-fool-proof-cam-sellection.82/
http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/
http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/
http://garage.grumpysperformance.com/index.php?threads/carb-intake-test.58/