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2.125" valve x .90 = 1.9125/2 = .95625 x .95625 = .9144 x 3.14 = 2.87 sqin.

5/16" stem.... .3125/2 = .15625 x .15625 = .0244 x 3.14 = .077 sqin.

2.87 - .077 = 2.79 sqin.

So a 2.125" valve is just a little on the small side to make 750hp at 7500 rpm with 12.5 cr. at 400 cuin. but can be done with a increase in VE.
From AFR's website on the 245's.

Minimum Cross Sectional Area
2.730 sq. in​

.200.300.400.500.550.600.650.700.800
Int161224261301311320331337345
Exh128165214228237238243245250

 

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Take this MBE SBC head, 2.32 intake valve and flows 495....


2.32/2 = 1.16 x 1.16 = 1.345 x 3.14 = 4.23 sqin. x 117 cfm/sqin = 494cfm, pretty close. So size does matter.
So just what is a good cfm per sq inch of valve area? I have some old flow numbers I got from Darin Morgan years ago.

RDP-SBX Australian Pro Stock Darin Morgan 2.27" intake valve 482 cfm @ 1"
► 482 / ((2.27/2)^2 * Pi) = 119.098

Chevy / GM SB2.2 NASCAR '05 - Darin Morgan 2.18" intake valve 453 cfm @ 1"
► 453 / ((2.18/2)^2 * Pi) = 121.3655

Chevy / GM RO7 - Darin Morgan 2.18 intake valve 459 cfm @1"
► 459 / ((2.18/2)^2 * Pi) = 122.973

Stan
 

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I got a PM telling me that Stan asked me a question (thanks), I have Stan on ignore as he is always asking me questions he knows the answer for instead of responding to the OP and I'm not going to play his "dick" games.

MBE heads posted they flowed 495 and producted 1195 hp = 2.414hp/cfm (2.9875 hp/cuin). The reason I did not use the throat size to calculate the cfm/squin. for the MBE heads as I did not know the % of the valve sized they used.

The AFR 245 heads.....345/2.79 = 124 cfm/sqin., not bad, lol, using a 90% throat.

345/2.73 = 126 cfm/sqin., even better using the mcsa.

MBE 2.32 x .90 = 2.088/2 = 1.044 x 1.044 = 1.09 x 3.14 = 3.422.....so 495/3.422 = 145 cfm/sqin for 90% throat.

Oh, the answer is the head/port/engine that produces the most hp/cuin/cfm.
 

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Just so there is an even comparison. But to be fair you are not going to see as good a cfm per sq inch of valve area from a 23 degree head as you will from a head has has a smaller valve incline angle.

AFR 2.125" intake valve 345 cfm @ 0.800"
345 / ((2.125/2)^2 * Pi) = 97.27726 CFM per sq. inch of Valve Area

Stan
 

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Looking at the AFR head @ .800" valve lift is interesting. But what if you are going to be running less than .800" valve lift?

Stan

Bore_=4.125_____Stroke=3.5______________Rod_Length=6.25_____RPM=_6500
Wrist_Pin_Offset_=0.0_____________________Number_of-Intake_Valves=1-Exhaust_Valves=_1
Intake_Valve_Size_=2.125__________________Exhaust_Valve_Size=_1.6
Intake_Valve_/Bore_Ratio=0.515152_______Exhaust_Valve/Bore_Ratio=_0.387879
Intake_Valve_Area_=3.546564_sq._in._______Exhaust_Valve_Area=_2.010619_sq._in.
Intake_Valve_Stem_Size_=0.3415____________Exhaust_Valve_Stem_Size=_0.3415
Intake_Valve_Stem_Area_=0.091595_sq._in.__Exhaust_Valve_Stem_Area=_0.091595_sq._in.
Valve_Lift_at_which_the_Valve_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=0.53125_Inches_________Exhaust_Valve_Lift=_0.4_Inches
Intake_Centerline_=111.0__________________User_Selected_DC-Discharge_Coefficient=_0.5
Throat_CSA_(0.9)Intake=2.7811_sq._in.___Throat_CSA(0.9)Exhaust=_1.5370_sq._in.
Effective_Throat_CSA_=0.88554_____________Effective_Throat_CSA=_0.87433
Valve_Lift_at_which_the_Throat_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=0.41659_Inches_________Exhaust_Valve_Lift=_0.30578_Inches
Intake_Valve_Seat_Angle_=45.0_____________Intake_Valve_Seat_Width=_0.045
Exhaust_Valve_Seat_Angle_=45.0____________Exhaust_Valve_Seat_Width=_0.045
User_-Intake_MCSA=2.73__________________User-Exhaust_MCSA=_1.57


Intake___------Curtain-----_Effective---Throat------Valve-------MCSA----
_Lift______CFM_____fps_______DC_____Area____Area______fps_______DC______fps_______DC______fps_______DC
_.2000__161.000__289.400___0.8262___1.335___1.103__138.937___0.3966__108.951___0.3110__141.538___0.4041
_.3000__224.000__268.429___0.7663___2.003___1.535__193.303___0.5518__151.583___0.4327__196.923___0.5622
_.4000__261.000__234.576___0.6696___2.670___1.788__225.233___0.6430__176.622___0.5042__229.451___0.6550
_.5000__301.000__216.421___0.6178___3.338___2.062__259.751___0.7415__203.690___0.5815__264.615___0.7554
_.5500__311.000__203.283___0.5803___3.672___2.131__268.381___0.7662__210.457___0.6008__273.407___0.7805
_.6000__320.000__191.735___0.5473___4.006___2.192__276.148___0.7883__216.548___0.6182__281.319___0.8031
_.6500__331.000__183.070___0.5226___4.339___2.268__285.640___0.8154__223.991___0.6394__290.989___0.8307
_.7000__337.000__173.075___0.4941___4.673___2.309__290.818___0.8302__228.052___0.6510__296.264___0.8457
_.8000__345.000__155.036___0.4426___5.341___2.364__297.722___0.8499__233.465___0.6665__303.297___0.8658
Avg_____287.889__212.780___0.6074___3.486___1.972__248.437___0.7092__194.818___0.5561__253.089___0.7225


Intake__%Step__--------CFM_per_Sq._In.-------____L/D___Lift___________Sq_In
_Lift______CFM__Increase___Throat____Valve__Curtain_____MCSA__Ratio___mm____M^3/s____Area____fps
.2000__161.000____________57.890___45.396__120.583___58.974_.094___5.08__0.0760___1.126__343.296
.3000__224.000____39.13___80.543___63.160__111.845___82.051_.141___7.62__0.1057___1.776__302.719
.4000__261.000____16.52___93.847___73.592___97.740___95.604_.188__10.16__0.1232___2.430__257.762
.5000__301.000____15.33__108.230___84.871___90.175__110.256_.235__12.70__0.1421___2.781__259.751
.5500__311.000_____3.32__111.825___87.691___84.701__113.919_.259__13.97__0.1468___2.781__268.381
.6000__320.000_____2.89__115.061___90.228___79.890__117.216_.282__15.24__0.1510___2.781__276.148
.6500__331.000_____3.44__119.017___93.330___76.279__121.245_.306__16.51__0.1562___2.781__285.640
.7000__337.000_____1.81__121.174___95.022___72.115__123.443_.329__17.78__0.1590___2.781__290.818
.8000__345.000_____2.37__124.051___97.277___64.598__126.374_.376__20.32__0.1628___2.781__297.722

Avg_____287.889___________103.515___81.174___88.658__105.454
 

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The problem is you need actual data because if the head doesn't move what the advertised numbers are, the math is off.

Think about this. If you port off velocity and you have a target. If the head moves more air, the actual size will be smaller than if the head isn't moving any air. In other words, the actual size is smaller than the calculated area. It's how we achieve 105+ VE.
 

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Discussion Starter · #88 ·
Heads showed up yesterday, they look like a really nice piece. Going to hopefully finalize the cam with Mark and get that going tomorrow morning. Looking like it’s going to be 274/[email protected]”, .740”/.735”, on a 110LSA. It’s a huge difference from what we have in there now. Using PAC 1225 springs, with titanium retainers.
 

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Discussion Starter · #90 ·
I told him no more than 200-250hp of nitrous. We’re using 1.65 rockers on both sides to get to that lift number. I wound up buying the heads assembled with the STD springs/ steel retainers, as nobody had sets with the upgraded springs and retainers in stock. So rather than waiting 2-3 months, we just bought the AFR P/N 8001 springs and 8505 retainers. I’ll use the take off springs and retainers on another, more mild engine. Mark did tell me that there’s more performance to be had with more cam timing and more aggressive lobes, but he felt this area is a better compromise of it running hard, and not being too harsh on valvetrain components. I trust his experience, and totally left the decision up to him on where we needed to be. He’s a great guy to deal with
 

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Couple years ago did a 429 SBC at 14.5 cr for a 10 Index car.Used AFR 220 Comp pkg OTB with a Mowtown 4150 Manifold with select porting.Made 741HP at 6700 rpms with Q16 fuel &carb Made 718 HP on C14 ..Made one hit in the car with throttle stop open .ran 9.51 at 142MPH .3350# Firebird
Cam is 268-280-111 .740-.700.
 

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I told him no more than 200-250hp of nitrous. We’re using 1.65 rockers on both sides to get to that lift number. I wound up buying the heads assembled with the STD springs/ steel retainers, as nobody had sets with the upgraded springs and retainers in stock. So rather than waiting 2-3 months, we just bought the AFR P/N 8001 springs and 8505 retainers. I’ll use the take off springs and retainers on another, more mild engine. Mark did tell me that there’s more performance to be had with more cam timing and more aggressive lobes, but he felt this area is a better compromise of it running hard, and not being too harsh on valvetrain components. I trust his experience, and totally left the decision up to him on where we needed to be. He’s a great guy to deal with
Do you wanna sell those 8001s. If so please pm me.
 

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Looking at the AFR head @ .800" valve lift is interesting. But what if you are going to be running less than .800" valve lift?

Stan

Bore_=4.125_____Stroke=3.5______________Rod_Length=6.25_____RPM=_6500
Wrist_Pin_Offset_=0.0_____________________Number_of-Intake_Valves=1-Exhaust_Valves=_1
Intake_Valve_Size_=2.125__________________Exhaust_Valve_Size=_1.6
Intake_Valve_/Bore_Ratio=0.515152_______Exhaust_Valve/Bore_Ratio=_0.387879
Intake_Valve_Area_=3.546564_sq._in._______Exhaust_Valve_Area=_2.010619_sq._in.
Intake_Valve_Stem_Size_=0.3415____________Exhaust_Valve_Stem_Size=_0.3415
Intake_Valve_Stem_Area_=0.091595_sq._in.__Exhaust_Valve_Stem_Area=_0.091595_sq._in.
Valve_Lift_at_which_the_Valve_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=0.53125_Inches_________Exhaust_Valve_Lift=_0.4_Inches
Intake_Centerline_=111.0__________________User_Selected_DC-Discharge_Coefficient=_0.5
Throat_CSA_(0.9)Intake=2.7811_sq._in.___Throat_CSA(0.9)Exhaust=_1.5370_sq._in.
Effective_Throat_CSA_=0.88554_____________Effective_Throat_CSA=_0.87433
Valve_Lift_at_which_the_Throat_Area_and_Window_/_Curtain_Area_are_the_SAME_SIZE
At_that_point_the_velocity_will_be_the_same_in_both_areas
Intake_Valve_Lift_=0.41659_Inches_________Exhaust_Valve_Lift=_0.30578_Inches
Intake_Valve_Seat_Angle_=45.0_____________Intake_Valve_Seat_Width=_0.045
Exhaust_Valve_Seat_Angle_=45.0____________Exhaust_Valve_Seat_Width=_0.045
User_-Intake_MCSA=2.73__________________User-Exhaust_MCSA=_1.57


Intake___------Curtain-----_Effective---Throat------Valve-------MCSA----
_Lift______CFM_____fps_______DC_____Area____Area______fps_______DC______fps_______DC______fps_______DC
_.2000__161.000__289.400___0.8262___1.335___1.103__138.937___0.3966__108.951___0.3110__141.538___0.4041
_.3000__224.000__268.429___0.7663___2.003___1.535__193.303___0.5518__151.583___0.4327__196.923___0.5622
_.4000__261.000__234.576___0.6696___2.670___1.788__225.233___0.6430__176.622___0.5042__229.451___0.6550
_.5000__301.000__216.421___0.6178___3.338___2.062__259.751___0.7415__203.690___0.5815__264.615___0.7554
_.5500__311.000__203.283___0.5803___3.672___2.131__268.381___0.7662__210.457___0.6008__273.407___0.7805
_.6000__320.000__191.735___0.5473___4.006___2.192__276.148___0.7883__216.548___0.6182__281.319___0.8031
_.6500__331.000__183.070___0.5226___4.339___2.268__285.640___0.8154__223.991___0.6394__290.989___0.8307
_.7000__337.000__173.075___0.4941___4.673___2.309__290.818___0.8302__228.052___0.6510__296.264___0.8457
_.8000__345.000__155.036___0.4426___5.341___2.364__297.722___0.8499__233.465___0.6665__303.297___0.8658
Avg_____287.889__212.780___0.6074___3.486___1.972__248.437___0.7092__194.818___0.5561__253.089___0.7225


Intake__%Step__--------CFM_per_Sq._In.-------____L/D___Lift___________Sq_In
_Lift______CFM__Increase___Throat____Valve__Curtain_____MCSA__Ratio___mm____M^3/s____Area____fps
.2000__161.000____________57.890___45.396__120.583___58.974_.094___5.08__0.0760___1.126__343.296
.3000__224.000____39.13___80.543___63.160__111.845___82.051_.141___7.62__0.1057___1.776__302.719
.4000__261.000____16.52___93.847___73.592___97.740___95.604_.188__10.16__0.1232___2.430__257.762
.5000__301.000____15.33__108.230___84.871___90.175__110.256_.235__12.70__0.1421___2.781__259.751
.5500__311.000_____3.32__111.825___87.691___84.701__113.919_.259__13.97__0.1468___2.781__268.381
.6000__320.000_____2.89__115.061___90.228___79.890__117.216_.282__15.24__0.1510___2.781__276.148
.6500__331.000_____3.44__119.017___93.330___76.279__121.245_.306__16.51__0.1562___2.781__285.640
.7000__337.000_____1.81__121.174___95.022___72.115__123.443_.329__17.78__0.1590___2.781__290.818
.8000__345.000_____2.37__124.051___97.277___64.598__126.374_.376__20.32__0.1628___2.781__297.722

Avg_____287.889___________103.515___81.174___88.658__105.454
Peak valve lift is never where demand is met.
 

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Chris Cobb at Dynotune Engineering did a dyno test on a 700 hp 434 from skip white. It made around 630 hp on his dyno. But with some modifications, another camshaft and porting to the AFR 220 heads it made over 700 hp !
Exactly!!!! Friend went through same shit.We had to redo complete engine to make anything out of the dung ball he paid way to much for.It ran like a shitty 355 let alone 430 plus.He is named right .I would 《skip》 anything he sells!!
 

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Discussion Starter · #98 ·
Had some time today to shim and swap the valve springs in the new heads. I should have the heads strapped down this weekend. Mark at bullet put the cam in for production- 274/[email protected]", .740"/.735", on a 110 LSA. Hopefully we'll have that in the next month or so. If I can get the heads on it this weekend, i may be able to get the exhaust system done too. We're taking the 1 3/4" x 3" Doug's headers off, and putting on the 1 7/8"x 3.5" lemons set. Gonna try and get some aluminum mufflers under it if we can fit them and still have decent ground clearance.
 
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