most guys use a tachometer on their car and shift at a set rpm range, the problem is that its not at all unusually for the time required to both react to the light flash and actually shift gears to take .2-.5 seconds during which time the engines still rapidly increasing its rpms, and its also not rare for clutches or torque converters to allow further rpm increases.
EXAMPLE
you set your typical street/strip 383 sbc, with its cam rated at 3000rpm-6400rpm,power band to let you know when to shift,you set the engines tachometer and shift light to flash at 6400rpm where you intend to shift, because piston speed and valve control issues in a typical 383 sbc will almost guarantee,youll run into durability issues if you shit much higher in the rpm band, if you have a data logger Id be very surprised if the engine did not exceed 6400rpm by at least 300rpm-500rpm or more between the time the light flashes and you complete the shift process, its not rare for that extra 300rpm-500rpm plus top cause the valve train to loose stability and if a piston kissed a valve bad things can result.
the answer from the cheap seat is to set the ignition revve limiter at 6500rpm and the shift light at a lower 6000rpm to compensate, but we ALL know your unlikely to do that even if testing shows the cars faster that way because your buddies all shift their 383 at 6500rpm or higher............for once in your life be smart and test the results, and have an engine that lasts a long time
BTW its not all that rare to install a TACH and find the car won,t start!, if the tachs wired wrong or if its defective it will ground the ignition, thus preventing the engine from running, so be aware of this and read instal instructions very carefully, IF you find the engine won,t run, don,t panic just put things back to original or use a multi meter to locate the problem,until you can test and isolate the cause
STUFF YOU SHOULD READ THRU!
keep in mind you want a SFI BILLET flywheel and a BLOW-PROOF BELL HOUSING
http://www.datsuns.com/Tech/whentoshift.htm
http://purplesagetradingpost.com/sumner ... index.html
viewtopic.php?f=80&t=1845&p=4824&hilit=+shift#p4824
viewtopic.php?f=71&t=555&p=1084&hilit=+shift#p1084
viewtopic.php?f=71&t=584&hilit=lakewood
viewtopic.php?f=53&t=343&p=6341&hilit=redline#p6341
viewtopic.php?f=53&t=204
EXAMPLE
you set your typical street/strip 383 sbc, with its cam rated at 3000rpm-6400rpm,power band to let you know when to shift,you set the engines tachometer and shift light to flash at 6400rpm where you intend to shift, because piston speed and valve control issues in a typical 383 sbc will almost guarantee,youll run into durability issues if you shit much higher in the rpm band, if you have a data logger Id be very surprised if the engine did not exceed 6400rpm by at least 300rpm-500rpm or more between the time the light flashes and you complete the shift process, its not rare for that extra 300rpm-500rpm plus top cause the valve train to loose stability and if a piston kissed a valve bad things can result.
the answer from the cheap seat is to set the ignition revve limiter at 6500rpm and the shift light at a lower 6000rpm to compensate, but we ALL know your unlikely to do that even if testing shows the cars faster that way because your buddies all shift their 383 at 6500rpm or higher............for once in your life be smart and test the results, and have an engine that lasts a long time
BTW its not all that rare to install a TACH and find the car won,t start!, if the tachs wired wrong or if its defective it will ground the ignition, thus preventing the engine from running, so be aware of this and read instal instructions very carefully, IF you find the engine won,t run, don,t panic just put things back to original or use a multi meter to locate the problem,until you can test and isolate the cause
STUFF YOU SHOULD READ THRU!
keep in mind you want a SFI BILLET flywheel and a BLOW-PROOF BELL HOUSING
http://www.datsuns.com/Tech/whentoshift.htm
http://purplesagetradingpost.com/sumner ... index.html
viewtopic.php?f=80&t=1845&p=4824&hilit=+shift#p4824
viewtopic.php?f=71&t=555&p=1084&hilit=+shift#p1084
viewtopic.php?f=71&t=584&hilit=lakewood
viewtopic.php?f=53&t=343&p=6341&hilit=redline#p6341
viewtopic.php?f=53&t=204
