Now there’s some rough guides available but Ill try to make this both logical and easy to understand
but since the possibilities are nearly endless you'll need to read thru the info and use the info posted to match YOUR components
There’s calculators, in the links to find the ideal compression ratio, port cross section and port length, header size etc, but you’ll actually need to READ THRU THE LINKS to get all the necessary info.
Power production is mostly about several factors and their limitations due to physical limitations to engine design and the fuel used and heat produced physical stress levels produced etc.
Well be discussing basic street strip engine combos in this thread
That limits us to components that will have the durability for longer term street use and meant to deal with pump gas octane levels, components like valve springs and cams should be expected to last in excess of 100K miles, without needing replacement
The engine should be at least marginally useful for daily transportation and getting stuck in slow traffic should not be a overheating death sentence to the combo.
You should expect the cars engine to operate at least semi smoothly below 3500 rpm, and pull to at least 6000rpm with out problems
The major factors
The size of the engine (its displacement)
this ones fairly easy, the power produced has an almost directly related ratio to the engines displacement, if all the other factors in two engine builds are extremely similar, I.E. the larger engine produces more hp/tq simply because you can produce x amount of hp/tq per cubic inch of displacement, or put a different way, if your combo produced 1.2 horsepower per cubic inch of displacement an engine of similar design that was 10% larger should produce an expected 10% increased power, and wile we will discuss some of those factors below in this thread ,keep that in mind, and if you don’t read thru the linked info and sub-links you’ll mill much of the useful info
viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152
The volumetric efficiency (how effectively you can fill and scavenge the cylinders) and the rpms you can do it at without valve train control issues
when you select an intake manifolds cams, heads etc. the goal is usually to maximize the engines volumetric efficiency, in the engines intended power band,(how efficiently you can fill the cylinders with a full fresh charge of fuel/air mix)
You’ll be limited in piston speed to about 4000fpm with stock components and 4500fpm with all balanced and forged components, in the rotating assembly.
Naturally the engines stroke length, and component weight,& strength plays an important part here
The valve train will vary, but as engine rpms increase the TIME the port has available to flow decreases and the stress on the valve train Increases dramatically
At 2500rpm there’s about 21 intake strokes flowing in theory a full cylinder volume of fuel/air mix thru the intake ports, past a moving valve, per second, at 7500rpm you’re trying to fill the cylinders almost 63 TIMES PER SECOND
And in the repeated 720 degree cycle there’s only about a maximum of 230-260 degrees of that 720 degrees that provide useful intake port flow rates, so your down to about 1/3 of the time the intake port can flow because the valves are CLOSED 2/3s of the time for all intents.
Port cross sectional areas should be small enough to provide good low rpm crisp response but large enough to not be a big upper rpm restriction, to flow, but keep in mind the intake runner length, cam timing and engines displacement and compression play a big part here, you can’t just pick a port volume and ignore the other factors, a 210cc port may not flow as well as a 180cc port , or the 180cc port may be highly restrictive to the combo, its design, flow rates at the cylinder,the cam timing its matched too and cross sectional area not its volume are the important factors.
Its silly to use a 210cc port that flows 300cfm on a sbc if its matched to a cam with a .450 lift, and 210 duration IF that port only flows lets say 200cfm at .450 lift , if a similar 180cc port flows lets say 230 cfm at that lift, its equally silly to use the same 180cc port heads with a .600 lift cam with 240 duration if the 210cc heads flow its full 300cfm at that lift and duration
ALL COMPONENTS NEED TO MATCH THE ENGINES INTENDED DISPLACEMENT,RPM RANGE, and INTENDED POWER CURVE,
the higher the average rpm range, and the higher the torque curve the higher the useable hp should be!
Your torque curve is basically the result of your displacement, compression and volumetric efficiency
the port flow rates, volumetric effiency and cam timing will dictate where the torque curve maxs out, in the rpm range.
your drive trains transmission and rear gearing will limit the rpm range you can effectively use most of the time!
but you should select a port size and flow rate (meassured at the cam your usings lift and keeping in mind its effective duration)and not spend time worring about the low speed characteristic simply because the low speed manors your engine will have are far more effected by other factors than cylinder head port size, yet the upper rpm flow will be certainly restricted if the ports too small in cross section or flow rate.you select components to slightly exceed the horsepower and torque goals, knowing that your engines rarely going to be performing at 100% efficiency
viewtopic.php?f=53&t=343
viewtopic.php?f=53&t=1168
viewtopic.php?f=53&t=253
viewtopic.php?f=53&t=510
http://www.fordmuscle.com/archives/2003/09/stroker/
viewtopic.php?f=44&t=742&p=1049#p1049
viewtopic.php?f=52&t=1477
viewtopic.php?f=50&t=1482&p=3337#p3337
viewtopic.php?f=52&t=181
viewtopic.php?f=52&t=528
viewtopic.php?f=52&t=399
viewtopic.php?f=52&t=322
viewtopic.php?f=52&t=333
viewtopic.php?f=52&t=1477
examples
here is a basic cam duration vs rpm band chart
Keep in mind the static compression MUST match the cam timing to allow the DYNAMIC COMPRESSION to fall in the 7.5-8.0:1 range for pump gas to be used, efficiently
Here is a basic port cross sectional area calculator
http://www.slowgt.com/Calc2.htm#MinCross
Here is a basic header calculator
http://www.slowgt.com/Calc2.htm#Header
theres a great deal more detailed info and many more calculators in the links and sub links posted in the thread
Air flow rates (how restrictive the ports, heads, valves, cam timing and exhaust are)
viewtopic.php?f=52&t=1563
viewtopic.php?f=52&t=333
viewtopic.php?f=52&t=425
viewtopic.php?f=52&t=148
viewtopic.php?f=52&t=92
viewtopic.php?f=56&t=260
viewtopic.php?f=56&t=185
viewtopic.php?f=56&t=961
Compression ratio (the higher you can go, within certain limits of course,(LIMITED TO THE OCTANE OF THE FUEL USED, AND HEAT PRODUCED)the more power you can produce)
viewtopic.php?f=52&t=183
viewtopic.php?f=52&t=112
viewtopic.php?f=52&t=240
posting.php?mode=edit&f=71&p=1048
but since the possibilities are nearly endless you'll need to read thru the info and use the info posted to match YOUR components
There’s calculators, in the links to find the ideal compression ratio, port cross section and port length, header size etc, but you’ll actually need to READ THRU THE LINKS to get all the necessary info.
Power production is mostly about several factors and their limitations due to physical limitations to engine design and the fuel used and heat produced physical stress levels produced etc.
Well be discussing basic street strip engine combos in this thread
That limits us to components that will have the durability for longer term street use and meant to deal with pump gas octane levels, components like valve springs and cams should be expected to last in excess of 100K miles, without needing replacement
The engine should be at least marginally useful for daily transportation and getting stuck in slow traffic should not be a overheating death sentence to the combo.
You should expect the cars engine to operate at least semi smoothly below 3500 rpm, and pull to at least 6000rpm with out problems
The major factors
The size of the engine (its displacement)
this ones fairly easy, the power produced has an almost directly related ratio to the engines displacement, if all the other factors in two engine builds are extremely similar, I.E. the larger engine produces more hp/tq simply because you can produce x amount of hp/tq per cubic inch of displacement, or put a different way, if your combo produced 1.2 horsepower per cubic inch of displacement an engine of similar design that was 10% larger should produce an expected 10% increased power, and wile we will discuss some of those factors below in this thread ,keep that in mind, and if you don’t read thru the linked info and sub-links you’ll mill much of the useful info
viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152
The volumetric efficiency (how effectively you can fill and scavenge the cylinders) and the rpms you can do it at without valve train control issues
when you select an intake manifolds cams, heads etc. the goal is usually to maximize the engines volumetric efficiency, in the engines intended power band,(how efficiently you can fill the cylinders with a full fresh charge of fuel/air mix)
You’ll be limited in piston speed to about 4000fpm with stock components and 4500fpm with all balanced and forged components, in the rotating assembly.
Naturally the engines stroke length, and component weight,& strength plays an important part here
The valve train will vary, but as engine rpms increase the TIME the port has available to flow decreases and the stress on the valve train Increases dramatically
At 2500rpm there’s about 21 intake strokes flowing in theory a full cylinder volume of fuel/air mix thru the intake ports, past a moving valve, per second, at 7500rpm you’re trying to fill the cylinders almost 63 TIMES PER SECOND
And in the repeated 720 degree cycle there’s only about a maximum of 230-260 degrees of that 720 degrees that provide useful intake port flow rates, so your down to about 1/3 of the time the intake port can flow because the valves are CLOSED 2/3s of the time for all intents.
Port cross sectional areas should be small enough to provide good low rpm crisp response but large enough to not be a big upper rpm restriction, to flow, but keep in mind the intake runner length, cam timing and engines displacement and compression play a big part here, you can’t just pick a port volume and ignore the other factors, a 210cc port may not flow as well as a 180cc port , or the 180cc port may be highly restrictive to the combo, its design, flow rates at the cylinder,the cam timing its matched too and cross sectional area not its volume are the important factors.
Its silly to use a 210cc port that flows 300cfm on a sbc if its matched to a cam with a .450 lift, and 210 duration IF that port only flows lets say 200cfm at .450 lift , if a similar 180cc port flows lets say 230 cfm at that lift, its equally silly to use the same 180cc port heads with a .600 lift cam with 240 duration if the 210cc heads flow its full 300cfm at that lift and duration
ALL COMPONENTS NEED TO MATCH THE ENGINES INTENDED DISPLACEMENT,RPM RANGE, and INTENDED POWER CURVE,
the higher the average rpm range, and the higher the torque curve the higher the useable hp should be!
Your torque curve is basically the result of your displacement, compression and volumetric efficiency
the port flow rates, volumetric effiency and cam timing will dictate where the torque curve maxs out, in the rpm range.
your drive trains transmission and rear gearing will limit the rpm range you can effectively use most of the time!
but you should select a port size and flow rate (meassured at the cam your usings lift and keeping in mind its effective duration)and not spend time worring about the low speed characteristic simply because the low speed manors your engine will have are far more effected by other factors than cylinder head port size, yet the upper rpm flow will be certainly restricted if the ports too small in cross section or flow rate.you select components to slightly exceed the horsepower and torque goals, knowing that your engines rarely going to be performing at 100% efficiency
viewtopic.php?f=53&t=343
viewtopic.php?f=53&t=1168
viewtopic.php?f=53&t=253
viewtopic.php?f=53&t=510
http://www.fordmuscle.com/archives/2003/09/stroker/
viewtopic.php?f=44&t=742&p=1049#p1049
viewtopic.php?f=52&t=1477
viewtopic.php?f=50&t=1482&p=3337#p3337
viewtopic.php?f=52&t=181
viewtopic.php?f=52&t=528
viewtopic.php?f=52&t=399
viewtopic.php?f=52&t=322
viewtopic.php?f=52&t=333
viewtopic.php?f=52&t=1477
examples
here is a basic cam duration vs rpm band chart
Keep in mind the static compression MUST match the cam timing to allow the DYNAMIC COMPRESSION to fall in the 7.5-8.0:1 range for pump gas to be used, efficiently
Here is a basic port cross sectional area calculator
http://www.slowgt.com/Calc2.htm#MinCross
Here is a basic header calculator
http://www.slowgt.com/Calc2.htm#Header
theres a great deal more detailed info and many more calculators in the links and sub links posted in the thread
Air flow rates (how restrictive the ports, heads, valves, cam timing and exhaust are)
viewtopic.php?f=52&t=1563
viewtopic.php?f=52&t=333
viewtopic.php?f=52&t=425
viewtopic.php?f=52&t=148
viewtopic.php?f=52&t=92
viewtopic.php?f=56&t=260
viewtopic.php?f=56&t=185
viewtopic.php?f=56&t=961
Compression ratio (the higher you can go, within certain limits of course,(LIMITED TO THE OCTANE OF THE FUEL USED, AND HEAT PRODUCED)the more power you can produce)
viewtopic.php?f=52&t=183
viewtopic.php?f=52&t=112
viewtopic.php?f=52&t=240
posting.php?mode=edit&f=71&p=1048