david vizard on choosing camshaft for specific applications

[67chevy]

while watching this seminar from david vizard i specifically wanted to post this one video because he explains the importance of a camshaft that matches your combination but also points out how alot of camshaft companies rely on a very "generic" approach for the most part when suggesting cams. i know grumpy has alot of camshaft related articles but i figured this might help someone as well. he has 6 of these videos on the subject of porting but this one was specifically based on matching the camshaft to specific cylinder heads/combination. the rest of the videos are very informative as well. http://www.youtube.com/watch?v=geKajuRCDPc

 

[grumpyvette]

Re: david vizard on choosing camshaft for specific applicati

as a general rule I see the most common mistake, made in selecting heads and matching cams to the application, tends to result from selecting a cam with bit too much duration and too wide of a LSA ,selecting heads with a bit too small of a port cross sectional area, and selecting a single plane intake for a street car engine ,where a dual plane would tend to work better.
few guys bother to calculate the correct rear gears, converter stall speed or measure the exhaust system back pressure.


heres that series of videos
http://www.youtube.com/watch?v=P6Watsamc9I

http://www.youtube.com/watch?v=-pMcIMj9kd0

http://www.youtube.com/watch?v=FerP1CUvPR8

http://www.youtube.com/watch?v=g4uUlaJED6k

http://www.youtube.com/watch?v=geKajuRCDPc

http://www.youtube.com/watch?v=oYZLUiRiUuY



FLOW BENCH , and related info ETC.
viewtopic.php?f=27&t=408&hilit=flow+bench

viewtopic.php?f=52&t=10145&p=39860&hilit=porting+help#p39860

viewtopic.php?f=52&t=8460&p=32923&hilit=porting+help#p32923

viewtopic.php?f=55&t=8485&p=29767&hilit=porting+help#p29767

viewtopic.php?f=52&t=462&hilit=porting+help

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=82

 

[grumpyvette]

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