http://www.chevytalk.org/fusionbb/showt ... 1229/tp/1/
viewtopic.php?f=69&t=461
viewtopic.php?f=69&t=261
THE PICTURE IS OF AN EXTERNALLY BALANCED ASSEMBLY, NOTICE THE COUNTER WEIGHT ON THE LOWER FLEX PLATE AND THE THICK PARTIAL RIM ON THE DAMPER
WHY BUILD A 383 SBC?
will it hurt my mileage?
will I need to change rear gears?
youll find the fuel mileage tends to drop slightly if your cars driven exactly the same way the 350 you currently have ,was,but the 383 has noticably more low rpm torque (generally youll find a 383 combo averages about 40ft lbs and 40 hp more than a similar 350 combo) that extra power that comes in earlier in the rpm band will allow you to shift earlier in the rpm band and still accellerate the car smoothly so a slight shift in the shift points will compensate to some extent, overall youll probably find only a very slight decrease in fuel mileage unless like some guys you find that your ability to produce tire smokes rather addictive
on the pluss side I get about 23 mpg with a 11:1 cpr 383 matched to an over drive trans IF I shift at about 2500rpm in most gears when IM driving like the old geezer I look like
it drops of noticably if IM shifting at 6300rpm
alot of your mileage concerns depend on your driving style, and your engine combos torque curve, it generally takes well under 100hp to cruise at 65mph at a steady speed and your trans will downshift if you tromp firmly on the accellerator,so you won,t be at 1500rpm if your passing some guy doing 60mph in the fast lane, youll generally find a 383 sbc will have little trouble cruiseing at 1500rpm if its got a mild cam and reasonably high compression and a OD trans helps average mileage
naturally the cam, compression ratio, intake selected and other factors will effect the power curve and your results but an over drive transmission and a reasonable rear gear ratio can give you some of the best of both, (PERFORMANCE AND MILEAGE), youll generally want the first gear ratio of your transmission and the rear gear ratio multipled to fall in the 10:1-11:1 range for a performance combo
read thru this
viewtopic.php?f=71&t=741
example
lets say you install a 4l80e with its .75 OD , but 2.48:1 first gear ratio, a 3.73:1- 3.90:1 rear gear will be a decent mileage and performance compromise range, your rpms at any speed can be easily calculated with the links info posted above if you know your cars tire dia.
In response to rfuchs
http://airflowresearch.com/articles/article085/A -P...
http://www.airflowresearch.com/sbc-195cc-c-72_92.h...
http://www.virtualengine2000.com/
viewtopic.php?...
viewtopic.php?...
by this cd/book
http://www.themotorbookstore.com/resmchstvi.html
read thru this info and take notes
viewtopic.php?f=69&t=461
viewtopic.php?f=69&t=261
THE PICTURE IS OF AN EXTERNALLY BALANCED ASSEMBLY, NOTICE THE COUNTER WEIGHT ON THE LOWER FLEX PLATE AND THE THICK PARTIAL RIM ON THE DAMPER
WHY BUILD A 383 SBC?
will it hurt my mileage?
will I need to change rear gears?
youll find the fuel mileage tends to drop slightly if your cars driven exactly the same way the 350 you currently have ,was,but the 383 has noticably more low rpm torque (generally youll find a 383 combo averages about 40ft lbs and 40 hp more than a similar 350 combo) that extra power that comes in earlier in the rpm band will allow you to shift earlier in the rpm band and still accellerate the car smoothly so a slight shift in the shift points will compensate to some extent, overall youll probably find only a very slight decrease in fuel mileage unless like some guys you find that your ability to produce tire smokes rather addictive
on the pluss side I get about 23 mpg with a 11:1 cpr 383 matched to an over drive trans IF I shift at about 2500rpm in most gears when IM driving like the old geezer I look like
it drops of noticably if IM shifting at 6300rpm
alot of your mileage concerns depend on your driving style, and your engine combos torque curve, it generally takes well under 100hp to cruise at 65mph at a steady speed and your trans will downshift if you tromp firmly on the accellerator,so you won,t be at 1500rpm if your passing some guy doing 60mph in the fast lane, youll generally find a 383 sbc will have little trouble cruiseing at 1500rpm if its got a mild cam and reasonably high compression and a OD trans helps average mileage
naturally the cam, compression ratio, intake selected and other factors will effect the power curve and your results but an over drive transmission and a reasonable rear gear ratio can give you some of the best of both, (PERFORMANCE AND MILEAGE), youll generally want the first gear ratio of your transmission and the rear gear ratio multipled to fall in the 10:1-11:1 range for a performance combo
read thru this
viewtopic.php?f=71&t=741
example
lets say you install a 4l80e with its .75 OD , but 2.48:1 first gear ratio, a 3.73:1- 3.90:1 rear gear will be a decent mileage and performance compromise range, your rpms at any speed can be easily calculated with the links info posted above if you know your cars tire dia.
In response to rfuchs
http://airflowresearch.com/articles/article085/A -P...
http://www.airflowresearch.com/sbc-195cc-c-72_92.h...
http://www.virtualengine2000.com/
viewtopic.php?...
viewtopic.php?...
by this cd/book
http://www.themotorbookstore.com/resmchstvi.html
read thru this info and take notes
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