How strong is the stock crank?
09-04-2005, 02:23 PM
#21
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more cubic inch likes more nitrous, more power isn't a concern of mine...if i can spend the same money and make 200+ more horsepower over a stock crank i'll do it. my first motor will be stock crank while the second motor is being built.
09-04-2005, 03:18 PM
#22
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I agree that you should use the stock crank and that you would want more bore than stroke in a N2O motor. The challenge will be to match the stock crank with a block and rotating assembly.
09-04-2005, 06:58 PM
#23
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i'm using a stock crank with a .030" over 6.0L block. Wiseco gas ported pistons and lunati pro billet rods. like i said this is my first motor and i'll be building another one a little more exotic after i get it running again. the stock crank motor will see a big shot and will be solid roller so it should be a good test of the stock parts.
09-05-2005, 12:03 AM
#24
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Originally Posted by bickelfirebird
I agree that you should use the stock crank and that you would want more bore than stroke in a N2O motor. The challenge will be to match the stock crank with a block and rotating assembly.
What do you guys think?
09-05-2005, 11:25 AM
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Originally Posted by liftin'em on nittos
i think it's a waste of money, but it's your car you do with it what you'd like. good luck
09-05-2005, 04:55 PM
#29
I don't think you're going to need the extra Cubic Inches. I'd run the largest bore for deshrouding purposes and add/subtract stroke to match Cubic Inch requirements of any race classes you wish to run. FWIW for something that may turn 8500 RPMS I'd be looking at a Truck crank and reworking the Rod Journals.
09-05-2005, 05:11 PM
#30
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which truck crank? 2 out of 3 of the truck motors use the same crank as the LS1. really it just depends on what you want out of the motor, what your goals are, and what your capable of building.
09-05-2005, 05:12 PM
#31
Originally Posted by liftin'em on nittos
which truck crank? 2 out of 3 of the truck motors use the same crank as the LS1. really it just depends on what you want out of the motor, what your goals are, and what your capable of building.
Floyd.
09-05-2005, 05:53 PM
#32
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4.8L crank with a 4" bore would be what...327cubic inches? that would be a good high rpm setup but wouldn't make the torque i would want out of something like that.
09-05-2005, 07:28 PM
#35
Sure, power down low matters in a street car, but once you start getting away from that and leaning towards a race setup it's not crucial to going fast. You want to make the most power in your range of engine operation, what happens outside of the range of operation doesn't make much of difference at least to me.
You keep brining up how important power down low is, yet you have a Carb intake manifold (probably single plane) in your signature, what's that going to do to your power in the lower rpm ranges as opposed to a FAST or LS6 intake?
Give and take we could probably argue until we're blue in the face, but anyway to each his own.
Floyd.
You keep brining up how important power down low is, yet you have a Carb intake manifold (probably single plane) in your signature, what's that going to do to your power in the lower rpm ranges as opposed to a FAST or LS6 intake?
Give and take we could probably argue until we're blue in the face, but anyway to each his own.
Floyd.
09-05-2005, 07:37 PM
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so you're telling you would rather make 500rwtq from 4500rpm to shift point as opposed to 500rwtq from 2500 rpm to shift point? my carb manifold motor will make more power/torque at 2500 rpm than most heads cam cars peak at. torque is what gets the car moving, the more of it you have the better off you are ESPECIALLY IN A RACE SETUP.
09-05-2005, 08:04 PM
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I'd rather have a 400 on the jug than a short stroke motor. Nitrious likes cubes, boost generally does better with less cubes.
TQ is what gets you outa the hole, I'd rather have a large amount of tq from a stroker setup, that still turned high rpm, rather than going with a high reving short, peaky, short stroke, peaky, AX/RR style setup...
Liftin'em, your motor doesnt need to worry about tq that low in the rpm, with the tranny/verter, you'll be above that on a footbrake.
TQ is what gets you outa the hole, I'd rather have a large amount of tq from a stroker setup, that still turned high rpm, rather than going with a high reving short, peaky, short stroke, peaky, AX/RR style setup...
Liftin'em, your motor doesnt need to worry about tq that low in the rpm, with the tranny/verter, you'll be above that on a footbrake.
09-05-2005, 08:23 PM
#39
Originally Posted by liftin'em on nittos
so you're telling you would rather make 500rwtq from 4500rpm to shift point as opposed to 500rwtq from 2500 rpm to shift point? my carb manifold motor will make more power/torque at 2500 rpm than most heads cam cars peak at. torque is what gets the car moving, the more of it you have the better off you are ESPECIALLY IN A RACE SETUP.
This exceptional amount of down low torque is why 383 (3.905X4.00) strokers go so much faster than built 348 (3.905X3.622) CID motors? OH WAIT those 383's don't go any quicker, but they sure do have more torque in the lower rpm range. Where it's not being used, ever in a race setup. However it's funny that they make the same amount of power on the big end and go similar speeds in the 1320 sprint.
Arguing that a 4.030X4.00 motor is going to have more potential than a Bigger bore (4.125) and shorter stroke (3.27) motor is about as gay as a football bat. Once you deshroud the valves by using a larger bore you almost always (99.9% of the time) gain flow on the cylinder heads. When you increase flow you also increase your flow factor potential, which increases power potential. With the 4.125X3.27 motor you're going to turn more RPM's easily, and effectively further increase your power potential.
To quote David Reher
Why does turning an engine higher make a race car run faster? This is my final column of the year, so I’ll offer my ideas and hope that they give racers something to think about over the winter break.
The simple explanation is that raising rpm effectively increases an engine’s displacement. This might seem nonsensical because the volume displaced by the pistons doesn’t change, but consider the effects of filling and emptying the cylinders faster in real time. An internal combustion engine is an air pump, and if we turn that pump faster, we can theoretically burn more fuel in a given amount of time and consequently produce more power. For example, an eight-cylinder engine running at 6,000 rpm fires its cylinders 24,000 times in one minute (assuming perfect combustion). Increase the engine’s speed to 8,000 rpm and it will fire 32,000 times per minute, a 33 percent increase. The volume of air and fuel that moves through the engine is now equivalent to an engine with a much larger displacement. There are also 8,000 additional power pulses per minute transmitted to the crankshaft that can be harnessed to turn the wheels and accelerate the car.
Raising engine speed is analogous to supercharging or turbocharging a motor; the goal is to increase the volume of air and fuel that moves through the engine. The airflow is increased with a forced induction system by pressurizing the intake system; in a naturally aspirated engine, the airflow is increased by raising rpm. If done correctly, both approaches will increase power.
A higher revving engine also permits the use of a numerically higher gear ratio to multiply the engine’s torque all the way down the drag strip. Let’s say an engine that produces 1,000 horsepower at 7,000 rpm is paired with a 4.56:1 rearend gear ratio. If this engine is then modified to produce 1,000 horsepower at 8,000 rpm, it can now pull a 4.88:1 or 5:14:1 rearend gear without running out of rpm before reaching the finish line. The numerically higher gear ratio gives the engine a mechanical advantage by multiplying its torque by a greater number to accelerate the car faster – in effect, it has a longer lever to move the mass.
The simple explanation is that raising rpm effectively increases an engine’s displacement. This might seem nonsensical because the volume displaced by the pistons doesn’t change, but consider the effects of filling and emptying the cylinders faster in real time. An internal combustion engine is an air pump, and if we turn that pump faster, we can theoretically burn more fuel in a given amount of time and consequently produce more power. For example, an eight-cylinder engine running at 6,000 rpm fires its cylinders 24,000 times in one minute (assuming perfect combustion). Increase the engine’s speed to 8,000 rpm and it will fire 32,000 times per minute, a 33 percent increase. The volume of air and fuel that moves through the engine is now equivalent to an engine with a much larger displacement. There are also 8,000 additional power pulses per minute transmitted to the crankshaft that can be harnessed to turn the wheels and accelerate the car.
Raising engine speed is analogous to supercharging or turbocharging a motor; the goal is to increase the volume of air and fuel that moves through the engine. The airflow is increased with a forced induction system by pressurizing the intake system; in a naturally aspirated engine, the airflow is increased by raising rpm. If done correctly, both approaches will increase power.
A higher revving engine also permits the use of a numerically higher gear ratio to multiply the engine’s torque all the way down the drag strip. Let’s say an engine that produces 1,000 horsepower at 7,000 rpm is paired with a 4.56:1 rearend gear ratio. If this engine is then modified to produce 1,000 horsepower at 8,000 rpm, it can now pull a 4.88:1 or 5:14:1 rearend gear without running out of rpm before reaching the finish line. The numerically higher gear ratio gives the engine a mechanical advantage by multiplying its torque by a greater number to accelerate the car faster – in effect, it has a longer lever to move the mass.
So you get an engine that can effectively use its better flowing heads, and turn more RPM's to make more power in the operating range. Many real engine builders will use the largest bore they can and use the stroke that fits the race class they are building the engine for.
Remember more Horsepower is nothing but a mathematical statement for Torque, so again it comes down to average power in the operating range.
09-05-2005, 08:28 PM
#40
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ok...you go figure out why promod guys run BIG stroke motors and HUGE shots of nitrous and run close to 9krpm then come back and chat with us. you build your short stroke high rpm motor i'll build my stroker and you can find me in the winners circle...