I recently had a guy stop by to discuss plans for his up-coming muscle car build up, he purchased a rather well worn 1970 tempest and wants to build a chevy V8 powered G.T.O. clone in appearance . he started talking about the difference in potential mileage between a 454 BBC and a 383 SBC and which he should be building.
his theoretical goal is 20mpg and 450 plus hp,while thats rather difficult , keep in mind the engines not going to be producing the 450plus hp while cruising so the rpm levels will be vastly different between the peak hp and lower cruise rpm levels, obviously an over drive transmission and tall tires should help.
the key here is thinking thru the combo and selecting an engine with good low rpm torque and mileage but good peak power.
I had him start thinking about his real goals, its silly, but darn few guys stop and think before they start building a car as to what they really want when they get it completed!, if your building a race car, youll want the basic car as light as you can build it and with the highest power to weight ratio you can get, and options like radios and air conditioning and heaters are thrown in the dumpster as useless dead weight to be scrapped. but if the cars rarely going to see the track, having a few things like comfortable seats and air conditioning makes sense.
you can get brisk street performance from either engine but its a great deal less work to build a mild big block and install an over drive transmission and rear gear ratio that allows the car to both cruise at lets say 2300rpm and smoke the tires occasionally than it will be with a 383 making similar horse power simply because to make similar horse power the 383 will need to operate at a higher average rpm range and its less likely to pull the car at lower rpms as easily.
the lighter the car weight and the lower the engine rpms while cruising the more likely you are to get exceptionally good mileage.
you can use the upper rpms and gearing for acceleration but its generally a compromise and to maintain good mileage , the engines got to be able to operate effectively in the 2300rpm-3000rpm cruise range, so that tends to favor the engine making good low and mid rpm torque.
I also pointed out that he also had the option of selecting the newer LS series aluminum engines and going with a MPFI or carb.
now I pointed out that it takes about 45hp to let his choice of cars cruise at a steady 60mph , so if hes going to be cruising and brutal acceleration or impressing the troops was not his goal, we could easily build a 383 sbc for his car, but if having access to both brutal acceleration and cruise manors were important and having a rather impressive engine compartment, the BBC option might be more valid, especially if the cars not a daily driven source of transportation.
the key here is taking the time to think things thru and make only the compromises you can live with. having a really fast car thats, noisy,hot, miserable to drive ,and uncomfortable on long trips, hardly makes much sense if you rarely go to the track and frequently take trips in the car, especially if your real goal is just occasional burn outs and your happy with a 12 second E.T. at the track, that beats 90% of the street cars you'll ever play with on the street, before you start any project you really need to honestly consider your skills, budget and goals. theres few of us that would not jump at the chance to install a 572 cubic inch big block in our cars, but thats hardly the best choice in a daily driver, in some applications and a salvage yard 5.3-5.7 liter LS , or a mild 383 sbc and an over drive transmission makes far more sense in most cases when the cars used as transportation rather than as a week end toy.
my suggestion was to think about it and lets start looking thru salvage yards for a late model truck thats wrecked as a source, for components with a larger v8 and over drive transmission to transplant the entire drive train and wiring etc. into his Pontiac.
viewtopic.php?f=44&t=775&p=8401&hilit=+what+takes+fast#p8401
viewtopic.php?f=87&t=677&p=5642&hilit=+what+takes+fast#p5642
viewtopic.php?f=87&t=3404&p=8992&hilit=weight+ratio+fast#p8992
viewtopic.php?f=87&t=489&p=3810&hilit=+what+takes+fast#p3810
viewtopic.php?f=69&t=1598&p=3766&hilit=+what+takes+fast#p3766
viewtopic.php?f=87&t=1162&p=2379&hilit=+what+takes+fast#p2379
his theoretical goal is 20mpg and 450 plus hp,while thats rather difficult , keep in mind the engines not going to be producing the 450plus hp while cruising so the rpm levels will be vastly different between the peak hp and lower cruise rpm levels, obviously an over drive transmission and tall tires should help.
the key here is thinking thru the combo and selecting an engine with good low rpm torque and mileage but good peak power.
I had him start thinking about his real goals, its silly, but darn few guys stop and think before they start building a car as to what they really want when they get it completed!, if your building a race car, youll want the basic car as light as you can build it and with the highest power to weight ratio you can get, and options like radios and air conditioning and heaters are thrown in the dumpster as useless dead weight to be scrapped. but if the cars rarely going to see the track, having a few things like comfortable seats and air conditioning makes sense.
you can get brisk street performance from either engine but its a great deal less work to build a mild big block and install an over drive transmission and rear gear ratio that allows the car to both cruise at lets say 2300rpm and smoke the tires occasionally than it will be with a 383 making similar horse power simply because to make similar horse power the 383 will need to operate at a higher average rpm range and its less likely to pull the car at lower rpms as easily.
the lighter the car weight and the lower the engine rpms while cruising the more likely you are to get exceptionally good mileage.
you can use the upper rpms and gearing for acceleration but its generally a compromise and to maintain good mileage , the engines got to be able to operate effectively in the 2300rpm-3000rpm cruise range, so that tends to favor the engine making good low and mid rpm torque.
I also pointed out that he also had the option of selecting the newer LS series aluminum engines and going with a MPFI or carb.
now I pointed out that it takes about 45hp to let his choice of cars cruise at a steady 60mph , so if hes going to be cruising and brutal acceleration or impressing the troops was not his goal, we could easily build a 383 sbc for his car, but if having access to both brutal acceleration and cruise manors were important and having a rather impressive engine compartment, the BBC option might be more valid, especially if the cars not a daily driven source of transportation.
the key here is taking the time to think things thru and make only the compromises you can live with. having a really fast car thats, noisy,hot, miserable to drive ,and uncomfortable on long trips, hardly makes much sense if you rarely go to the track and frequently take trips in the car, especially if your real goal is just occasional burn outs and your happy with a 12 second E.T. at the track, that beats 90% of the street cars you'll ever play with on the street, before you start any project you really need to honestly consider your skills, budget and goals. theres few of us that would not jump at the chance to install a 572 cubic inch big block in our cars, but thats hardly the best choice in a daily driver, in some applications and a salvage yard 5.3-5.7 liter LS , or a mild 383 sbc and an over drive transmission makes far more sense in most cases when the cars used as transportation rather than as a week end toy.
my suggestion was to think about it and lets start looking thru salvage yards for a late model truck thats wrecked as a source, for components with a larger v8 and over drive transmission to transplant the entire drive train and wiring etc. into his Pontiac.
viewtopic.php?f=44&t=775&p=8401&hilit=+what+takes+fast#p8401
viewtopic.php?f=87&t=677&p=5642&hilit=+what+takes+fast#p5642
viewtopic.php?f=87&t=3404&p=8992&hilit=weight+ratio+fast#p8992
viewtopic.php?f=87&t=489&p=3810&hilit=+what+takes+fast#p3810
viewtopic.php?f=69&t=1598&p=3766&hilit=+what+takes+fast#p3766
viewtopic.php?f=87&t=1162&p=2379&hilit=+what+takes+fast#p2379
