Re: david vizard on choosing camshaft for specific applicati
heres free cam selection software to narrow your choices
just for grins put your info into this program, and don,t lie, and see what cam it suggests
http://www.camquest.com/
http://www.compcams.com/Pages/409/camquest-6.aspx
AS your displacement per cylinder increases the effective valve size per cubic inch decreases so you need a slightly tighter LSA , to allow more effective exhaust scavenging of the cylinder volume during the valve over-lap timing, and these charts should help.
but I must point out that the major reason you want that tighter LSA is to allow effective cylinder scavenging with the exhaust inertia helping to drag in the following intake charge as the low pressure at the exhaust port caused by the rapid exiting gases in the headers if the cam timing is correctly matched to the application draws gases into and partial out of the cylinder while both valves are open during the over lap period.
increasing the cam duration past a certain pint determined by several factors such as engine displacement, effective compression and header scavenging efficiency in a set rpm band is usually counter productive, as it tends to bleed off the next intake charge volume.
if done correctly this will increase the efficiency of the cylinder fill rates, and flush out a higher percentage of the remaining previously burnt exhaust gases.
I think this chart above is frequently either ignored or mis-understood
let me show an example
lets say your building a big block 496 with the typical oval port after market heads having 2.19' diam. intake valves and its got 10.7:1 compression.
a 496 displacement has 62 cubic inches per cylinder, if you look at the chart and divide 62 by 2.19 you get 28.3, look at the chart! that would strongly suggest a 100-102 LSA (LOBE SEPARATION ANGLE be selected,) GOOD LUCK FINDING A CAM FOR A BIG BLOCK WITH THAT LSA!
heres a chart I found that I don,t fully agree with, I think its a bit conservative, by about 3%-5% on the required cam duration ,required to avoid detonation with todays crappy octane fuel, but it at least gives you a base to work from, but Id suggest selecting a bit more duration
software like the free comp cams software below
http://www.compcams.com/Camquest/default.asp
viewtopic.php?f=52&t=333
youll also find these links and sub links useful
viewtopic.php?f=69&t=9930
viewtopic.php?f=69&t=5123
the required stall has little to do with the type of lifter your using, its need, to be used, or changed is determined by the rpm range of the cam you select and your car weight,the cars automatic transmission first gear ratio, tire diameter and rear gear ratio.
a mild roller cam would work with a stock stall converter just as a mild flat tappet lifter cam will.
the whole idea of swapping to a higher stall speed torque converter is to allow the engine UNDER LOAD to jump in rpm up into the engines most efficient power range or the most effective part of the torque curve.
http://garage.grumpysperformance.co...electing-a-torque-converter-stall-speed.1715/
http://garage.grumpysperformance.co...hing-the-drive-train-to-the-engine-combo.741/
http://garage.grumpysperformance.com/index.php?threads/more-converter-stall-speed.12964/
http://garage.grumpysperformance.co...mbers-or-a-good-street-combo-your-after.5078/
http://garage.grumpysperformance.co...d-high-spring-pressures-don-t-work-well.1489/
http://garage.grumpysperformance.com/index.php?threads/matching-parts-and-a-logical-plan.7722/
http://garage.grumpysperformance.co...gine-to-match-the-cam-specs.11764/#post-55651