GUYS TELL YOU A 210CC air flow research HEADS GOING TO ABSOLUTELY KILL Torque ON A 383 BUT ITS FINE FOR A 400 SBC, WHAT TOTAL b.s, your cylinder heads port size needs to be selected with both displacement and the intended rpm/power band in mind and a 10% change in engine displacement may or may not require a change in port size, as other factors, like the ports minimum cross sectional area and shape, valve curtain area, cam timing,compression ratio, intake runner length and cross section, and your exhaust header design,etc. will have as large or a larger effect results.
look thru the linked info theres calculators , listed in the links and sub-links that can be used to accurately calculate the correct port cross sectional area, and runner length, matching header config cam timing etc.
theres a HUGE MIS -CONCEPTION out there that its always the larger port cross sectional area on any engine that lacks low speed torque, thats responsible for a loss of low speed torque, in most cases it is the combo of a larger than ideal for the application cam duration and a single plane intake, and larger and shorter headers or a restrictive exhaust having been selected ,NOT the cylinder heads port size.
YES cylinder head port cross section will effect the port velocity, but in most cases if your building a performance street cars engine your better off going slightly larger on port size and slightly conservative on the cam duration. and a good dual plane intake and long tube headers with a low restriction exhaust sure helps.


viewtopic.php?f=52&t=8460
viewtopic.php?f=52&t=8460&p=32923&hilit=curtain+flow+angle#p32923
viewtopic.php?f=52&t=322
viewtopic.php?f=52&t=10602
http://www.strokerengine.com/SBCHeadsFlow.html
viewtopic.php?f=69&t=9879
When you see cylinder heads listed as lets say 177cc or 190cc or 210cc port heads thats a reference to the internal intake port runner volume, and while larger port heads tend to flow more air theres no direct linear link, an exceptional 190cc port can out flow a marginal 210cc port, and the shape of the port and its length also effect its volume, a change in port volume of 5% alone with no other change is almost meaningless it the effect it has on engine torque ,compared the intake,runner design, exhaust,or header configuration, compression and cam timing
valve seat and back face angles ,valve diameter and valve lift and duration effect the flow thru the curtain area






PORT MATCHING THE INTAKE RUNNER EXIT TO THE CYLINDER HEAD PORT ENTRANCE USUALLY HELPS REDUCE RESTRICTIONS TO FLOW RATES, AND REDUCES FUEL/AIR DISTRIBUTION ISSUES

keep in mind there are tools that can be used to measure air pressure at different points in an intake port that can be used to accurately calculate air flow speeds, and youll moss a ton of info if you don,t read the sub links




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





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
http://www.circletrack.com/enginetech/1 ... ch_engine/

keep in mind in most cases youll want to select a intake port that will allow the highest air flow rates without getting into port stall or making the port cross sectional area restrict flow.
youll find that the average cylinder head intake gasket is about 10%-15% LARGER IN CROSS SECTIONAL AREA THAT THE NARROW SECTION OF MOST INTAKE PORT EITHER DUE TO THE PORT RESTRICTION NEAR THE PUSH RODS OR VALVE THROATS.
ideally youll want to select a port cross sectional area that will provide near 300fps in air flow rates at or near the intended power peak, which in most performance engines will be close to reaching critical piston durability rpm levels.
on most engines using good performance components thats about 4300fpm in piston speeds.
viewtopic.php?f=53&t=343&p=419&hilit=redline#p419
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



http://www.circletrack.com/techarticles ... ewall.html
the guys that tell you you should have used 195cc heads on your 383,sbc , and will all point to the larger 210cc head as having lower port flow speeds,...WELL, while thats true, BUT ONLY UP TO A POINT, AND IT MIGHT NOT, BE IN YOUR COMBOS BEST INTEREST TO GO WITH THE SMALLER PORT SIZE the amount of the port flow reduction is all but meaningless, IN MANY APPLICATIONS AT ANY RPM POINT, if you ask them how much the port flow was reduced you'll never get a firm intelligent answer because they don,t have a clue, and are just repeating , like mindless parrots,
repeating crap they heard. DO YOU REALLY THINK SUBTRACTING 4% FROM THE DISPLACEMENT OR ADDING 1% TO THE PORTS CROSS SECTIONAL AREA WILL HURT THE TORQUE NEARLY [b]AS MUCH AS THE ADDED PORT FLOW HELPS THE UPPER RPM POWER CURVE
the difference between those two heads in cross sectional area,is about 1%
the 210cc heads superior,provided your trying to maximize the combos power potential and are running the engine up into its peak potential power band, PORT FLOW SPEEDS WILL BE EQUAL OR HIGHER JUST 200RPM HIGHER IN THE POWER CURVE WITH THAT 383 VS A 400SBC. and your correct the cam, intake and other factors far out weight the difference in port cross section and flow speed differences, any reduction in torque is due to lower compression, a different cam or the intake or header design not the port size difference, and the 210cc head has a marked advantage with the larger cams[/b] JUST REMEMBER THE 210CC HEADS ARE DESIGNED FOR sbc combos WITH CAMS WITH OVER about .550 LIFT AND OVER about 245 DEGS DURATION AT .050 LIFT, AND COMPRESSION RATIOS OVER 10.5:1 IF YOUR LOOKING TO GET THE FULL ADVANTAGE FROM THE PORT DESIGN, AND DISPLACEMENTS OF 377 PLUS.
now obviously if your running a much smaller cam duration,in the 220-230 @50 lift and under .530 lift low 9:1 or lower compression and a restrictive intake, there's not much point in installing killer heads where you'll never get close to the the larger ports full flow potential
many guys will tell you that selecting oval port heads is better on a street car engine, and they generally have a point, yet depending on compression ratio and cam used you may never notice any loss of low rpm torque, if you select a reasonable size rectangular port head and matched components ,this is one of the huge semi-myths about big block engines.
while its true that the low rpm torque does tend to be reduced with stock oval port heads vs stock rectangular port heads ,its also true that the compression, intake manifold, cam timing,rear gearing and header designs all change the results and its very easy to build a rectangular port engine that destroys tires, and theres a huge range in size of the ports in BOTH oval and rectangle port aftermarket heads
http://www.carcraft.com/techarticles/cc ... ewall.html
[color:red]read the article[/color]
Peaks and Averages
................Avg. TQ Avg. HP Peak TQ Peak HP
Iron .. ........541.1 475.0 595 .........521
Edelbrock 582.1 514.9 618 ........582
Dart .......... 584.2 517.7 615 .......595
TFS ................590.3 522.5 626 ... 595
Brodix .....590.8 ........523.0 626 ........597
here read thru these LINKS THERE'S LOTS OF GOOD INFO! and some CALCULATORS YOU CAN USE, and remember the basic concepts apply to both bbc and sbc engines but naturally the port sizes and flow rates and cam timing needs to match the application
a few hours spent reading links can save you a great deal of wasted time, and a great deal of wasted money
http://www.airflowresearch.com/articles ... 1/A-P1.htm
http://www.tmossporting.com/tabid/1805/Default.aspx
http://racingfeed.com/downloads/chevy_flow_data.pdf
http://www.strokerengine.com/SBCHeadsFlow.html
http://www.wallaceracing.com/area-under-curve.php
viewtopic.php?f=56&t=3155&p=37090&hilit=redline#p37090
viewtopic.php?f=55&t=58&p=36446#p36446
http://www.j-performance.com/index.php? ... view&id=48
A VERY USEFUL set of CALCULATORs
http://www.rbracing-rsr.com/runnertorquecalc.html
http://users.erols.com/srweiss/calccsa.htm
http://users.erols.com/srweiss/calcplv.htm
http://users.erols.com/srweiss/calcfps.htm
viewtopic.php?f=53&t=341&p=30714&hilit=redline#p30714
http://www.s262612653.websitehome.co.uk ... /heads.htm
http://users.erols.com/srweiss/calcacsa.htm
http://www.wallaceracing.com/max-rpm2.php
viewtopic.php?f=52&t=10947&p=48126#p48126
http://www.gofastnews.com/board/technic ... uding.html
http://www.gofastnews.com/board/technic ... lumes.html
http://www.circletrack.com/enginetech/c ... index.html
viewtopic.php?f=99&t=6461&p=20464&hilit=head+flow+numbers#p20464
viewtopic.php?f=55&t=1038&p=6713#p6713
http://www.wallaceracing.com/max-rpm2.php
viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152
viewtopic.php?f=52&t=322
http://www.j-performance.com/index.php? ... view&id=28
viewtopic.php?f=52&t=5364&p=16066&hilit=head+flow+numbers#p16066
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.jsme.or.jp/esd/COMODIA-Procs ... 4_P535.pdf
http://www.compcams.com/Community/Articles/Details.asp?ID=1737510521
http://www.slowgt.com/Calc2.htm#MinCross
http://users.erols.com/srweiss/tablehdc.htm
http://www.malcams.com/legacy/misc/headflow.htm
viewtopic.php?f=50&t=575
http://airflowresearch.com/articles/article115/A-P1.htm
viewtopic.php?f=55&t=624
viewtopic.php?f=52&t=796
http://airflowresearch.com/articles/article031/A-P1.htm
http://www.chevyasylum.com/chp/
viewtopic.php?f=52&t=1563&p=11966&hilit=head+flow+numbers#p11966
viewtopic.php?f=50&t=1482&p=3509&hilit=volumetric#p3509
http://victorylibrary.com/mopar/intake-tech-c.htm
http://www.carcraft.com/techarticles/11 ... index.html
viewtopic.php?f=52&t=92&p=116#p116
viewtopic.php?f=52&t=2203&p=13143&hilit=head+flow+numbers#p13143
http://www.brodix.com/media/images/page_2.jpg
http://www.dartheads.com/customer_servi ... .php?qk=34
http://users.erols.com/srweiss/tablehdc.htm
viewtopic.php?f=52&t=90
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
DYNO DON POSTED THIS BIT OF INFO
"AFR 195 Eliminators
actual cc's in the intake port.....184
cross section area...2.13 sq.in
Flow spec's.....281/221
AFR 195 comp Eliminators
actual cc's ....189
cross section...2.15 sq.in
Flow spec's...306/235
Trick Flow 195 K D
before porting actual cc's....185
after porting ...188
cross section....2.13 sq.in
Flow spec's....270/210
Edelbrock Etec 200's
actual cc's before porting N/A
after porting....197
cross section...2.13
Flow spec's...270/218
"

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
your ports cross section selection should depend on the cars gearing , displacement, compression ratio,and average rpm range and the cam timing you'll be using, a 12:1 cpr 383 with a .650 lift cam that spends most of its time in the 4500rpm-7500rpm band will take a larger port cross section , than a 9:1 cpr 383 with a .450 lift cam that spends most of its time in the 1500rpm-5500rpm band. or a 350 will work out best with a 180cc port vs a 195cc or even a 200cc port size, ok I understand WHY your thinking that way but Id doubt you've done the math if you still hold that position, here is why, the 195cc port has a cross sectional area of about 2.15 sq inches MAX, the 180 cc ports run close to 2.1 sq inches ,MAX MOST ARE SMALLER IN CROSS SECTIONAL AREA, but think about this, a 2.02" intake valve that's .450" off its seat has a flow curtain of about 2.86sq inches
2.02" diam x pi 3.147 x .450"=2.86sq inches even at that low lift.
the intake runner design and intake plenum and the cam timing, displacement and compression ratio will have far more effect on the port flow than a simple swap from 180cc to 200cc in the head port size
it does absolutely no good to place a cylinder head with with a port cross sectional area [b]thats larger than the intake port that feeds it,beyond the intake runner exit, in a combo as all the abrupt increase in port cross section does is cause increased turbulence, and a sudden loss of port air flow speed and that tends to cause fuel to drop out of the airflow or at least disrupt is even distribution
in an ideal world ports reduce cross sectional area bye about 3% from entrance to the valve pocket, and the port cross section in the heads a bit smaller than the intake runner.
the port flow is limited by the ports smallest cross section not its largest
http://www.wallaceracing.com/max-rpm2.php
http://www.rbracing-rsr.com/runnertorquecalc.html
viewtopic.php?f=44&t=10910
making even the larger port a restriction, and in any case a difference of about 3%in cross sectional area is in effect meaningless to flow rates [/b]
port throats generally run 80%-85% of total valve diameter because you need to maintain sufficient valve seat contact area to allow sealing and cooling and some wear during operation
