valve size and duration?

bc · Post by bc » Wed Dec 21, 2005 10:46 am

How do you know how much duration and lift you need with a certain valve size to achieve the rpm that you want. I thought there was a formula around here but I cant find it when I do a search. Im building a 496 with a 2.17 intake valve size and want peak hp around 6500. Anyone know about how much duration and lift I would need to get there.

67RS502 · Post by **67RS502** » Wed Dec 21, 2005 12:30 pm

There was a formula for a curtain area and port size here not too long ago.
I would think the min. port cross section would be included in this, as it will pay a part in the peak rpm.

dbusch · Post by **dbusch** » Wed Dec 21, 2005 1:17 pm

not sure of the formula, but i can tell you that running a 2.17 valve with a 496 is going to require a BIG cam to reach your goal. That size engine should have more like a 2.300 intake valve in it, then you wouldnt have to have such a radical cam.

Post by **maxracesoftware** » Wed Dec 21, 2005 5:09 pm

with a 2.170 Intake Valve

Code: Select all

496.049 Cubic Inches @ 6500 RPM with 100.0 % Volumetric Efficiency PerCent
Required Intake  Flow between  298.9 CFM  and  316.4 CFM  at 28 Inches
Required Exhaust Flow between  241.6 CFM  and  258.9 CFM  at 28 Inches

600 RPM/Sec Dyno Test	Low		Normal		Best
Peak HorsePower    	688.2		698.8		709.3
Peak Torque Lbs-Ft 	616.5		625.9		635.4

HorsePower per CID    	1.387		1.409		1.430
Torque per Cubic Inch 	1.243		1.262		1.281

BMEP in psi           	187.4		190.3		193.2
Carb CFM at 1.5 in Hg.	933		1038		1143

Target EGT= 1298 degrees F during 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2  Method  = 104.1 to 106.8  Octane required range
Air Standard Efficiency = 62.989 % for 12.000:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test	Lowest		Average		Best Potential
Head Flow Peak HP = 	431.6		680.0		762.7

               ----- Engine Design Specifications -----

Engine Size CID      = 496.049		Intake Valve Net Area    = 3.589
CID per Cylinder     = 62.006		Intake Valve Dia. Area   = 3.698
Rod/Stroke Ratio     = 1.444		Intake Valve Stem Area   = 0.109
Bore/Stroke Ratio    = 1.014		Exhaust Valve Net Area   = 2.667
Int Valve/Bore Ratio = 0.503		Exhaust Valve Dia. Area  = 2.776
Exh Valve/Bore Ratio = 0.436		Exhaust Valve Stem Area  = 0.109
Exh/Int Valve Ratio  = 0.866		Exh/Int Valve Area Ratio = 0.751

Intake Valve L/D Ratio= .323		Exhaust Valve L/D Ratio= .362
CFM/Sq.Inch = 80.8 to 85.6		CFM/Sq.Inch =87.0 to 93.3

Curtain Area -to- Valve Area Convergence  Intake Valve Lift = .543
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift = .470

Intake Valve Margin CC's		Exhaust Valve Margin CC's
1.00 CC = 0.0165			1.00 CC = 0.0220
0.50 CC = 0.0083			0.50 CC = 0.0110
0.25 CC = 0.0041			0.25 CC = 0.0055
0.10 CC = 0.0017			0.10 CC = 0.0022

             -------  Piston Motion Data  -------
Average Piston Speed         (FPM)= 4604.16 in Feet Per Minute
Maximum Piston Speed         (FPM)= 7658.58 occurs at 72.669 Degrees ATDC
Piston Depth at 72.669 degree ATDC= 1.8370 inches  Cylinder Volume= 439.2 CC
Maximum TDC Rod Tension     GForce= 3433.34 G's
Maximum BDC Rod Compression GForce= 1666.79 G's


             -------  Current Camshaft Specs @ .050  -------

IntOpen= 22.50	IntClose= 62.50		ExhOpen= 70.00	ExhClose= 30.00
Intake Duration @ .050  = 265.00	Exhaust Duration @ .050 = 280.00
Intake CenterLine   = 110.00		Exhaust CenterLine  = 110.00
Compression Duration= 117.50		Power Duration      = 110.00
OverLap Duration = 52.50		Lobe Center Angle (LCA)= 110.00
Camshaft installed Straight Up = 0.00 degrees




-Recommended Camshaft Valve Lift-       - Induction System Tuned Lengths -
         Minimum  Normal  Maximum	Best Length= 14.088    2nd= 11.089
Intake  = 0.744   0.801   0.882		3rd Best= 8.997   4th Best= 7.569
Exhaust = 0.732   0.788   0.867		Plenum Runner Max Entry Area = 4.917
Max-effort  Intake Lift = 0.924		Minimum Plenum Volume CC = 1232.9
Max-effort Exhaust Lift = 0.908		Minimum Plenum Volume CID= 75.2

Minimum Intake Valve Lift to prevent Choke = .801 Lift  @  6500 RPM



        -------  Operating RPM Ranges of various Components  ------- 

Camshaft Intake Lobe RPM = 6701		Exhaust Lobe RPM = 6676
Camshaft's Intake and Exhaust Lobes operating RPM range = 4694 to 6694
Note=> Lobe RPMs are valid only for conventional 2-Valve Pushrod Engines

Current  (Intake Valve Curtain Area -VS- Time)  Choke  RPM = 5677 RPM

Intake Valve Area + Curtain Area operating RPM Range = 4113 to 6113 RPM

Intake Valve Diameter RPM Range = 4677 to 6677

Intake Flow CFM @28in RPM Range = 4483 to 6483



with a 2.300 Intake Valve =>

Intake Valve L/D Ratio= .304		Exhaust Valve L/D Ratio= .362
CFM/Sq.Inch = 71.9 to 76.2		CFM/Sq.Inch =80.0 to 88.0

Curtain Area -to- Valve Area Convergence  Intake Valve Lift = .575
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift = .470

Intake Valve Margin CC's		Exhaust Valve Margin CC's
1.00 CC = 0.0147			1.00 CC = 0.0220
0.50 CC = 0.0073			0.50 CC = 0.0110
0.25 CC = 0.0037			0.25 CC = 0.0055
0.10 CC = 0.0015			0.10 CC = 0.0022

             -------  Piston Motion Data  -------
Average Piston Speed         (FPM)= 4604.16 in Feet Per Minute
Maximum Piston Speed         (FPM)= 7658.58 occurs at 72.669 Degrees ATDC
Piston Depth at 72.669 degree ATDC= 1.8370 inches  Cylinder Volume= 439.2 CC
Maximum TDC Rod Tension     GForce= 3433.34 G's
Maximum BDC Rod Compression GForce= 1666.79 G's


             -------  Current Camshaft Specs @ .050  -------

IntOpen= 22.50	IntClose= 62.50		ExhOpen= 70.00	ExhClose= 30.00
Intake Duration @ .050  = 265.00	Exhaust Duration @ .050 = 280.00
Intake CenterLine   = 110.00		Exhaust CenterLine  = 110.00
Compression Duration= 117.50		Power Duration      = 110.00
OverLap Duration = 52.50		Lobe Center Angle (LCA)= 110.00
Camshaft installed Straight Up = 0.00 degrees




-Recommended Camshaft Valve Lift-       - Induction System Tuned Lengths -
         Minimum  Normal  Maximum	Best Length= 14.088    2nd= 11.089
Intake  = 0.702   0.756   0.832		3rd Best= 8.997   4th Best= 7.569
Exhaust = 0.691   0.744   0.818		Plenum Runner Max Entry Area = 4.917
Max-effort  Intake Lift = 0.871		Minimum Plenum Volume CC = 1232.9
Max-effort Exhaust Lift = 0.857		Minimum Plenum Volume CID= 75.2

Minimum Intake Valve Lift to prevent Choke = .756 Lift  @  6500 RPM



        -------  Operating RPM Ranges of various Components  ------- 

Camshaft Intake Lobe RPM = 6814		Exhaust Lobe RPM = 6789
Camshaft's Intake and Exhaust Lobes operating RPM range = 4808 to 6808
Note=> Lobe RPMs are valid only for conventional 2-Valve Pushrod Engines

Current  (Intake Valve Curtain Area -VS- Time)  Choke  RPM = 6017 RPM

Intake Valve Area + Curtain Area operating RPM Range = 4359 to 6359 RPM

Intake Valve Diameter RPM Range = 5501 to 7501

Intake Flow CFM @28in RPM Range = 4483 to 6483

about .050" less Valve Lift on Camshaft with 2.300 vs 2.170

sorry for the way Data comes out formatted in this Post

Post by **Stevespeed** » Wed Dec 21, 2005 5:23 pm

Maxrace, which version of your software are you using to produce this data? Looks awesome!

Post by **maxracesoftware** » Wed Dec 21, 2005 5:29 pm

Maxrace, which version of your software are you using to produce this data? Looks awesome!

this LINK
http://www.maxracesoftware.com/pipemax_win.htm

starting at *** Version 3.0 ***
towards the middle of page to the bottom

one day i'll take the time to figure out how to Post
this Data so it doesn't get Formatted so badly

its too much Data to Post anyway..takes up too much of
SpeedTalk's valuable Web space

bc · Post by bc » Wed Dec 21, 2005 6:02 pm

Wow thanks alot! I really need to get that software!

scottm · Post by **scottm** » Thu Dec 22, 2005 1:40 am

its too much Data to Post anyway..takes up too much of
SpeedTalk's valuable Web space

no way! It is this kind of info that MAKES Speedtalks web space so valuable. Thank you for sharing

bc · Post by bc » Fri Dec 23, 2005 3:19 pm

I was looking at this again and if Im reading this right. It says that you only need 316cfm for 496cid engine at 6500rpm to make 700hp with 100%VE. I would have thought you need more than that cfm wise. The heads that are going on this engine will flow 380 to 400cfm once done.