port and runner math

[grumpyvette]

read this, BUT keep in mind it does little good to have killer head flow numbers if the intake manifold flows less or if the exhaust is restricting flow, and heads that flow killer numbers at .700 lift, and are designed to feed a 427 displacement at 7500rpm, DON,T do you much good if the CAM you sellected has a .520 lift AND ONLY SPIN THE ENGINE TO 6000RPM

http://www.tmossporting.com/tabid/1805/Default.aspx

http://www.airflowresearch.com/super-chevy-apr-2010-210cc-sbc.php
you might want too look thru this link also
http://www.weldtech.com/productsframe.html

USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations[/color]
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
BTW.
ITS A COMMON MISCONCEPTION,THAT YOU MEASURE PORT CROSS SECTION AT THE PORT ENTRANCE,BUT ITS NOT the port area at the entrance , you need to use in the calcs, ITS the MINIMAL port cross section at the SMALLEST point in the port, usually near the push-rod area.
LIKE a funnel, its not the largest part of the opening but the smallest thats the restriction to flow

SO HOW do you MEASURE THEN??

http://www.harborfreight.com/cpi/ctaf/d ... umber=5649

http://store.summitracing.com/partdetai ... toview=sku

USE THIS

http://www.rbracing-rsr.com/runnertorquecalc.html

on the better 23 degree SMALL BLOCK AFTERMARKET HEADS THERE'S ABOUT 5.5 INCHES OF INTAKE PORT LENGTH ON AVERAGE FROM INTAKE GASKET TO THE BACK OF THE INTAKE VALVE AT THE FAR EDGE

http://users.erols.com/srweiss/tablehdc.htm

http://www.malcams.com/legacy/misc/headflow.htm

here,s a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some common cross sectional port sizes
(measured at the smallest part of the ports)
...........................sq inches........port cc
edelbrock performer rpm ....1.43.............170
vortec......................1.66.............170
tfs195......................1.93.............195
afr 180.....................1.93.............180
afr 195.....................1.98.............195
afr 210.....................2.05.............210
dart pro 200................2.06.............200
dart pro 215................2.14.............215
brodix track 1 .............2.30.............221
dart pro 1 230..............2.40.............230
edelbrock 23 high port .....2.53.............238
edelbrock 18 deg............2.71.............266
tfs 18 deg..................2.80.............250

Potential HP based on Airflow (Hot Rod, Jun '99, p74):
Airflow at 28" of water x 0.257 x number of cylinders = potential HP
or required airflow based on HP:
HP / 0.257 / cylinders = required airflow
I know from experience not one guy in a hundred will take the effort to actually measure so I figured I,d try to keep the idea, I was posting about, rather easy to grasp, keep the math minimal ,and hope the point gets thru.
THINK OF COMPONENT SELECTION AS A PROCESS OF ELIMINATING THE WEAK LINK IN A CHAIN!
keep in mind it does you little good to have a SBC cylinder head that flows 310cfm at .700 lift, if you install a cam with .550 max lift,or UNDER ABOUT 245 DURATION at .050 lift or matched to an intake that flows 270cfm , or an exhaust pipe thats restrictive to exhaust flow at peak rpms

I can,t begin to tell you the number of times Ive grabbed snap gauges and a dial caliper and got questioned about what I was measuring when checking port throat restrictions or runner cross sections.
and in case some guys still don,t grasp it the point is that your dealing with a rather complex system with several potential restrictions and simply throwing a good flowing intake on an engine or increasing the rocker ratio may or may not provide an increase in flow potential, the result depends on how the rest of the components flow and react to the component being changed or the mods you've done, there's always several components that act like weak links in the chain, so locating those and improving those gets the best results, but of course once they are radically improved other components can become the new weak link or restriction.
so your trying to maintain a balance that potentially allows you to reach and exceed the power goals while hopefully not going bankrupt

400 cu in (6.6 L) SBC (1970-1981)150–265 hp (112–198 kW) 155cc-165cc intake port size
396 and 402 BBC 255 cc intake port size
The 396-cubic-inch (6.5 L) V8 was introduced in the 1965 Corvette as the L78 option and in the Z16 Chevelle as the L37 option. It had a bore of 4.094 in (104.0 mm) and a stroke of 3.760 in (95.5 mm),[8][9] and produced 375 hp (280 kW) and 410 lb⋅ft (560 N⋅m). The solid lifter version was capable of being operated in the upper 6000 rpm range, and when installed in the 1965 Corvette, was factory-rated at 425 horsepower.

Introduced in 1970, the 402-cubic-inch (6.6 L) was a 396-cubic-inch bored out by 0.030 in (0.76 mm). Despite the fact that it was 6 cubic inches (98 cc) larger, Chevrolet continued marketing it under the popular "396" label in the smaller cars while at the same time labeling it "Turbo-Jet 400" in the full-size cars. Power rating(s) by year:

• 1966: 325 hp (242 kW)/350 hp (260 kW)/360 hp (270 kW)/375 hp (280 kW)
• 1967: 325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
• 1968: 325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
• 1969: 265 hp (198 kW)(2bbl)/325 hp (242 kW)/350 hp (260 kW)/375 hp (280 kW)
• 1970: 330 hp (250 kW)/350 hp (260 kW)/375 hp (280 kW)
• 1971: 300 hp (220 kW) SAE gross; SAE net hp was 260 for dual exhaust and 206 for single exhaust
• 1972: 240 hp (180 kW) SAE net for dual exhaust and 210 hp SAE net for single exhaust

having a valve spring micrometer of the correct size and knowing how to use it helps a great deal
a good deal of the results you see on the EXHAUST side AND THE INTAKE SIDE are greatly effected by the scavenging design rpm range of the headers and the restriction to flow beyond the collectors.
YOU CAN,T CRAM MORE IN TILL THE OLD F/A CHARGE VOLUME IS REMOVED, and with a properly designed low restriction exhaust , the fast moving exhaust mass in the headers helps to drag in the next intake charge into the cylinders.
generally you can get a bit of useful info with a pressure gauge, if the exhaust have greater than about 1 PSI you've generally got a restriction thats hurting the power,and that restriction to flow DOES effect the engine tuning results and the cam timing you-ll want to use.
now Ive generally found that the collector lengths on commercial headers are too short and in many cases designed wrong to maximize the cylinder scavenging.
it does little good to stick a decent set of headers on a car and then hook the collectors up to a restrictive 2" or 2.5" exhaust either.
if your car runs noticeably better with open headers at the track, you can bet your street exhaust is restrictive.

viewtopic.php?f=56&t=1730&p=5392&hilit=horse+power+from+flow#p5392

there ARE aftermarket header merge collectors and things you can do to reduce the restriction to flow, (THE (H) and (X) pipes that split or share the exhaust between both sides, and a custom 3" exhaust and low restriction mufflers comes instantly too mind here)

every component selected is a compromise in some area, stock Chevy small block intake ports run 145cc-170cc in most cases they are generally designed to maximize the 1000rpm-4500rpm power band , the aftermarket "smaller" 180cc ports keep the port velocity and torque high in lower rpms and provide a very noticeable improvement over the stock heads and are a better match to stock rear gears and mild cams
yes you can jump to the 195cc-200cc port size but you tend to loose some low rpm response and torque, swapping to a 3.73:1 rear gear and a 3000rpm stall converter allows you to make more high rpm power with a larger duration cam and bigger heads and still have a good low rpm power potential because your able to jump up into a higher average part of the power band on demand, and not be required to slowly work up to the required rpms , its generally the 2500-2800rpm and below where the larger heads cause the response to be a bit soggy , being able to skip that at wide open throttle helps, but keep in mind the, engine displacement, compression ratio, headers, intake, cam, and other factors also effect your results

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=5078&p=14840#p14840

http://forum.grumpysperformance.com/viewtopic.php?f=44&t=38

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=5364

viewtopic.php?f=50&t=1266

viewtopic.php?f=52&t=975&p=1700&hilit=210cc#p1700

http://users.erols.com/srweiss/tablehdc.htm

viewtopic.php?f=52&t=4532&p=12045&hilit=bushing+timing#p12045

viewtopic.php?f=32&t=5521

http://www.j-performance.com/index.php? ... view&id=48

viewtopic.php?f=52&t=1070&p=2054#p2054

 

[enigma57]

Great info, Grumpy! Also wanted to thank you for the info regarding GMPP 215cc vortec Bowtie heads on the thread at CT......

http://www.chevytalk.org/fusionbb/showt ... id/264471/

I was looking at it from the standpoint of a 383 daily driver turning only moderate RPMs on the street, rather than a serious race engine build where the engine will regularly see much higher revs. I fully understand where you are coming from and appreciate your guidance in that regard.

Many thanks,

Harry

 

[grumpyvette]

don,t get fixated on cylinder head port size potentially adding or restricting torque too much,if you are worried about selecting a port size thats a bit to large, its a MINOR factor compared too
compression,
cam timing
displacement, header design,
and intake design
you can still make great power and torque if the other components are sensibly selected, even if you used 215cc port heads on a 355 sbc, but obviously you should take the effort to match the port size to the intended operational rpm band, cam timing and compression, plus the cars drive train gearing and intended shift points ETC.
you just might make the torque a bit higher in the rpm range and need to change the rear gearing to optimize the results

valve seat and back face angles ,valve diameter and valve lift and duration effect the flow thru the curtain area

keep in mind that valve may be forced off its seat, too full lift and re-seating 50 plus TIMES A SECOND at near 5500 rpm, so theres very little TIME for gases to move through the very restrictive space between the valve seat and valve edge

Calculating the valve curtain area
The following equation mathematically defines the available flow area for any given valve diameter and lift value:
Area = valve diameter x 0.98 x 3.14 x valve lift
Where 3.14 = pi (π)
For a typical 2.02-inch intake valve at .500-inch lift, it calculates as follows:
Area = 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches

• advancing or retarding the camshaft to adjust your DCR
• 
• when you advance a cam what your doing is moving all the timing points in relation too, the crank rotation, so the valves open and CLOSE earlier, thus the intake valve seats trapping a bit more volume, of fuel/air mix thats going to be compressed as the piston rises toward TDC, remember nothings compressed to be ignited and burn, until both valves seal, as the piston rises on the compression stroke, this increases pressure and heat, boosting lower rpm torque.
• retarding the valve seating and sealing by retarding the cam timing reduces the volume of gases being compressed at lower rpms but due to inertia and the exhaust scavenging at higher rpms this retarding the cam does not usually have nearly as much effect on upper rpm power due , that it has on the engine at lower rpms due too the lower trapped low speed volume being trapped and burnt, the inertia and scavinging by the exhaust header can actually increase the mass of trapped gases over the piston at a certain designed rpm range

http://garage.grumpysperformance.co...ng-cam-and-shifting-the-lca.10553/#post-44949

http://garage.grumpysperformance.com/index.php?threads/dynamic-vs-static-compression.727/#post-5575

http://garage.grumpysperformance.com/index.php?threads/cam-gear-and-timing-marks-etc.724/#post-1021

http://garage.grumpysperformance.co...hanics-of-adv-ret-a-camshaft.4532/#post-12045

• why do nearly all manufacturers grind their camshafts "dual-pattern" with more lift & duration on the exhaust side?
• longer exhaust timing on a cam,allows greater time for the exhaust gases to bleed off,this compensates to some extent for a restrictive stock exhaust manifold and exhaust system, but its seldom required or useful with open tuned headers

http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

http://garage.grumpysperformance.co...-between-shorty-and-full-length-headers.1303/

• why most cams are ground 4 degrees advanced and under what conditions should we install 4 degrees retarded to "undo" this

cam manufactures learned very quickly that some customers tended to be impressed with ADVERTISED DURATION AND LIFT, this commonly resulted in less informed customers (the vast majority) purchasing a larger and longer duration cam than the engine required, advancing the cam tended to add a little extra low speed drive-ability reducing the number of customer complaints when the larger than needed cam was installed

http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/

http://garage.grumpysperformance.com/index.php?threads/split-cam-and-cam-suggestion.12294/

http://garage.grumpysperformance.co...bit-of-extra-cam-lobe-exhaust-duration.11080/

http://garage.grumpysperformance.com/index.php?threads/cam-analysis-pointers-by-harvey-crane.10460/

http://garage.grumpysperformance.com/index.php?threads/lca-or-lsa.11523/#post-53156

http://garage.grumpysperformance.com/index.php?threads/cams-explained.324/#post-48613
example
viewtopic.php?f=52&t=266&p=322&hilit=215cc+vortec#p322

http://airflowresearch.com/articles/art ... A19-P1.htm

http://airflowresearch.com/articles/article094/A-P1.htm

http://airflowresearch.com/articles/article054/A-P1.htm

viewtopic.php?f=52&t=5537

 

[grumpyvette]

one topic of discussion I hear frequently is guys that have just installed a larger than stock cam, and frequently larger valves and better valve springs along with a performance aftermarket cam, in their engines expecting the changes made to noticeably increase the engines power, but what results in some cases is the car becomes a DOG, because of several factors like,
the rear gear ratio won,t match the cams intended power band
the converter stall speed won,t allow the engine to easily reach the new intended power rpm range
the intake or cylinder heads port and runner flow rates can,t supply the required increase air flow rates'
the exhaust flow rates effectively restricts flow thru the heads
. one example I find is guys who spend money to increase the valve size on vortec heads, from the stock 1.94" to the larger valves like in chevy fuelie heads that had 2.02 valves, the increased valve curtain area with the larger 2.02 vs 1.94" valves has almost no effect on lower rpm torque, the engine will produce, but it does have a measurable increase in upper rpm flow, but your vortec intake ports, cross sectional area, restrict air flow to the point the increased valve curtain area is all but useless ,what killed your low rpm torque , in cases where you added a larger duration cam, along with, or without adding larger valves was most likely installing a cam with more duration that required for the application, or one larger than the port flow can support.
EXAMPLE a bit of time running calculations shows a vortec head with its 1.66 square inch of port cross sectional area matched to a 383 will produce good power in the 3000-3500rpm band and above up too about 4700rpm, where the port is incapable of keeping up with demand.. stick a cam in that engine designed to operate in the 3500rpm-6500rpm band and youve killed off much of the cars potential power band

USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.wallaceracing.com/chokepoint.php
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm

keep in mind that the port cross sectional area can be easily calculated and its most effective port speed will fall in a set rpm band, swapping to a cam that is designed to operate at a higher rpm range will kill off low rpm torque and have very limited benefits in the upper rpms
this is a very common mistake guys make in not taking the time to measure and calculate how parts must match the intended power band.
if you read thru the links youll find that it states a couple times that its basically a waste of money and effort to swap to the larger 2.02 valves, the reason is simple the cross sectional area of the port on the un-ported stock vortec heads is more restrictive than the curtain area of the valve at full lift.
while its true the 2.02 valve potentially increased the flow as its a larger curtain area the restriction in the port falls in the port push rod pinch area restriction, thus even with the increased curtain flow its not much of a help to total flow thru the port
think of the port throat restriction like the weak link in a chain, thats 6 feet long, hanging from an over head hoist, place that weak link at the 3 foot point and if a link will fail at lets say a 1000lb load is the weak link, you can add all the 1200 lb rated chain links below that point you choose yet the chain still fails at that weak link regardless of the increased strength of the lower chain used.
this is why its critical to carefully match parts, it does you little good to have an aftermarket intake manifold or heads that flow 300 cfm, if the valve lift you select never allows that level of flow, it won,t make any difference if you have killer heads that flow 310 cfm, if the intake manifold is restricted to 240cfm, or if you put together a matched set that flows 300cfm thats capable of making 600hp if you use a stock exhaust manifold and stock exhaust system with 2" pipes designed for a 307 sbc that would rarely exceed 3500rpm,that won,t allow the engine exhaust to exit without excessive back pressure, its a system, not a collection of parts, and the systems restricted by the least efficient components used.

http://garage.grumpysperformance.com/index.php?threads/sellecting-cylinder-heads.796/#post-49711

casting numbers on the stock production 170cc port vortec heads
10239906 and 12558062..96-up...350.........."Vortec 5700", "L31", 64cc chamber,
170cc intake port, 1.94"/1.5" valves

you should read this related info also

http://www.vetteweb.com/tech/vemp_1303_ ... n_systems/

http://www.jegs.com/i/GM+Performance/80 ... 6/10002/-1

GM Performance 25534446
THERES ALSO A LARGE PORT VERSION THATS FAR SUPERIOR FOR MAKING PEAK HP, the 170cc versions designed to produce max torque at about 4000rpm on a 350 displacement and youll have a hard time exceeding 450 hp, with those heads, the large ports can support 600hp with minor port work

READ THESE LINKS AND SUB LINKS

viewtopic.php?f=44&t=4462&p=12023&hilit=vortec+block+restrictive#p12023

viewtopic.php?f=52&t=266&p=322&hilit=215cc+vortec#p322

http://www.summitracing.com/parts/nal-25534446

viewtopic.php?f=69&t=1040&p=1943&hilit=215cc+vortec#p1943

http://www.hughesengines.com/TechArticles/1headflowchartscomparisons.php

RELATED INFO< WELL WORTH READING
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