How to tell if headers are too small?

[kid vishus]

Besides spending a lot of money on new ones that is.

My motor does not respond to changes in the intake system. My fuel system is good, my ignition is good, etc. I have changed camshafts 3 times, non are substantially better than any others. I cannot beleive that between 2 different brands, and 3 different grinds, none of them are better than the others. I changed intakes, went from a tall professionally ported single plane to a home ported short single plane, and it ran exactly the same; same 60', same half track, same ET, same mph. I changed carbs, went from a 950HP to a 1050 dominator, and it still ran almost exactly the same; 60' slowed just a touch, et was the same with a little more mph. I think I could make it a little better with some more tuning, but not enough to make the motor run anywhere near what it should. It does not miss, or sputter, or not pull hard, it just doesn't run fast or respond to any exterior changes. I am thinking either my headers are too small and causing a restriction in the system, or my convertor is junk and it doesn't care what the motor is doing it's only going to go so fast.

The guys I got the motor from were running headers much bigger than I currently am, and I think maybe it is because it needs it.

Am I barking up the right tree for a change, or am still looking in the wrong areas?

[dbusch]

we need as much info on this combp as you can come up with. maybe Larry will run your deal thru pipemax to see what headers you need...

[kid vishus]

The motor is a 402 inch smallblock ford. 4v cleveland heads, stock port diameter on the exhaust side, 1.71 exhaust valve. They flow 246 @ .700, 249 @ .750. Intake side flows 357 @ .700, 360 @ .750. Grp rods 6.250" in length, 15-1 compression, 4" stroke. Bullet solid roller cam 276/288 @ .050, 310/322 adv, .722/.702 lift, 108 lsa. The car weighs 2800 lbs with driver, 4.86 gear, 14x32's, 5400 rpm TCI (POS?) convertor, 'glide with 1.82 low. I currently shift it at 7000. I am currently running Hooker super comps with 1 7/8" primaries and 3 1/2" collectors. The guys I got the motor from were running headers with 2" stepped to 2 1/8" primaries with a 4" collector. I can get a set of 2 1/8" primary headers for it, but I am learey of spending $600 on ~shelf~ headers if they arent going to help and may require an act of Congress to get them in the car.

If I forgot anything, smack me upside the head and let me know.

[dbusch]

what ETs does it run, 60ft, mph, etc.

[Transman]

Converter sounds a tad too tight for a combination like yours. Not sure where your torque peak is at, but most of the combinations along the lines of yours that I've worked with respond quite well to at least 6K for stall speed. If you have sufficient tire/suspension then go with a converter that has a more agressive stator, especially since I believe you're footbraking it (or very trusting of that 1.82 gearset, lol). I'd look at some things besides just headers. And, there's not a darned thing wrong with TCI's converters. I just did a trans/converter for a guy back here to replace his ATI 8" and dropped .5 off his ET. 10.72 to 10.22, plus a jump in mph as well, with a TCI 8" converter.

[kid vishus]

what ETs does it run, 60ft, mph, etc.

Slow

Normal 60' is around 1.44-1.46 footbraking, et's in the upper 6.40's (6.47 or so) at almost 108 mph (107.5-107..

[kid vishus]

I believe you're footbraking it (or very trusting of that 1.82 gearset, lol).

Yep, but I just hooked the 'brake up and the 2 step, gonna see how many passes till it breaks.

One thing I dont like about the convertor is, it was originally done by JW, then sent to TCI to be ~freshened~. I'm not a big fan of sending someone else's stuff to a different company and have them go thru it regardless of who's it was originally. But it came with the trans, so I couldn't really complain about it.

[larrycavan]

I saw the post and ran it through my copy of Larry Meaux's Pipe Max for you.....Got to Love That Program!

I had to guesstimate some specs...I'm a bike guy so I'm not familiar with car engine specs off the top of my head...anyway...here's what it came up with...

Intake Valve size - 2.190?


402.125 Cubic Inches @ 7000 RPM with 125.0 % Volumetric Efficiency PerCent
Required Intake Flow between 345.6 CFM and 366.4 CFM at 28 Inches
Required Exhaust Flow between 240.2 CFM and 269.8 CFM at 28 Inches

600 RPM/Sec Dyno Test Low Normal Best
Peak HorsePower 817.7 827.7 837.6
Peak Torque Lbs-Ft 670.6 678.8 687.0

Exhaust Data

--- Single Primary Pipe Specs --- for 402.125 CID engine at 7000 RPM
Diameter= 1.736 to 1.861 Length= 26.7 to 29.2 inches long

--- 2-Step Primary Pipe Specs ---
1st Dia.= 1.736 Length= 13.4 to 14.6
2nd Dia.= 1.861 Length= 13.4 to 14.6

--- 3-Step Primary Pipe Specs ---
1st Dia.= 1.736 Length= 13.4 to 14.6
2nd Dia.= 1.861 Length= 6.7 to 7.3
3rd Dia.= 1.986 Length= 6.7 to 7.3

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3.187 to 3.437 Tuned Lengths= 15.2 best and also 7.6 or 30.4

--- Header Collector Specs (Megaphone or Diffuser Cone Shape) ---
Diameter= 2.687 taper to 3.687 Megaphone/Diffuser Length= 15.2 inches

Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness

[kid vishus]

Intake Valve size - 2.190?

Correct

Peak HorsePower 817.7 827.7 837.6
Peak Torque Lbs-Ft 670.6 678.8 687.0

There lies the problem, I'm making maybe 550.

[Unkl Ian]

Stupid question time:

Do you know for sure that you are getting full throttle ?
Are the timing marks in the right place ?

[larrycavan]

Ok, then here's the rest of the data to work with. Sometimes cutting and pasting things screws up the column alinements....if you want I can dump everything to text and email it to you....


402.125 Cubic Inches @ 7000 RPM with 125.0 % Volumetric Efficiency PerCent
Required Intake Flow between 345.6 CFM and 366.4 CFM at 28 Inches
Required Exhaust Flow between 240.2 CFM and 269.8 CFM at 28 Inches

600 RPM/Sec Dyno Test Low Normal Best
Peak HorsePower 817.7 827.7 837.6
Peak Torque Lbs-Ft 670.6 678.8 687.0

HorsePower per CID 2.033 2.058 2.083
Torque per Cubic Inch 1.668 1.688 1.708

BMEP in psi 251.5 254.6 257.6
Carb CFM at 1.5 in Hg. 1018 1133 1247

Target EGT= 1086 degrees F during 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 116.9 to 115.0 Octane required range
Air Standard Efficiency = 69.040 % for 15.000:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 492.8 784.6 881.9

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

Engine Size CID = 402.125 Intake Valve Net Area = 3.674
CID per Cylinder = 50.266 Intake Valve Dia. Area = 3.767
Rod/Stroke Ratio = 1.563 Intake Valve Stem Area = 0.093
Bore/Stroke Ratio = 1.000 Exhaust Valve Net Area = 2.204
Int Valve/Bore Ratio = 1.095 Exhaust Valve Dia. Area = 2.297
Exh Valve/Bore Ratio = 0.855 Exhaust Valve Stem Area = 0.093
Exh/Int Valve Ratio = 0.781 Exh/Int Valve Area Ratio = 0.610

Intake Valve L/D Ratio= .330 Exhaust Valve L/D Ratio= .411
CFM/Sq.Inch = 45.9 to 48.6 CFM/Sq.Inch =52.3 to 58.7

Curtain Area -to- Valve Area Convergence Intake Valve Lift = .548
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift = .428

Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0162 1.00 CC = 0.0266
0.50 CC = 0.0081 0.50 CC = 0.0133
0.25 CC = 0.0041 0.25 CC = 0.0066
0.10 CC = 0.0016 0.10 CC = 0.0027

------- Piston Motion Data -------
Average Piston Speed (FPM)= 4666.66 in Feet Per Minute
Maximum Piston Speed (FPM)= 7699.64 occurs at 73.706 Degrees ATDC
Piston Depth at 73.706 degree ATDC= 1.7410 inches Cylinder Volume= 358.5 CC
Maximum TDC Rod Tension GForce= 3674.22 G's
Maximum BDC Rod Compression GForce= 1892.78 G's


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

IntOpen= 30.00 IntClose= 66.00 ExhOpen= 72.00 ExhClose= 36.00
Intake Duration @ .050 = 276.00 Exhaust Duration @ .050 = 288.00
Intake CenterLine = 108.00 Exhaust CenterLine = 108.00
Compression Duration= 114.00 Power Duration = 108.00
OverLap Duration = 66.00 Lobe Center Angle (LCA)= 108.00
Camshaft installed Straight Up = 0.00 degrees




-Recommended Camshaft Valve Lift- - Induction System Tuned Lengths -
Minimum Normal Maximum Best Length= 14.010 2nd= 11.027
Intake = 0.336 0.358 0.381 3rd Best= 8.947 4th Best= 7.527
Exhaust = 0.327 0.349 0.371 Plenum Runner Max Entry Area = 4.293
Max-effort Intake Lift = 0.428 Minimum Plenum Volume CC = 1076.3
Max-effort Exhaust Lift = 0.407 Minimum Plenum Volume CID= 65.7

Minimum Intake Valve Lift to prevent Choke = .336 Lift @ 7000 RPM



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

Camshaft Intake Lobe RPM = 15121 Exhaust Lobe RPM = 15727
Camshaft's Intake and Exhaust Lobes operating RPM range = 13272 to 15272
Note=> Lobe RPMs are valid only for 4 or 5-Valve Overhead Cam Engines

Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 14580 RPM

Intake Valve Area + Curtain Area operating RPM Range = 20818 to 22818 RPM

Intake Valve Diameter RPM Range = 14778 to 16778

Intake Flow CFM @28in RPM Range = 5396 to 7396
___________________________________________________________________________

Best estimate RPM operating range from all Components = 6848 to 8848

Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding
___________________________________________________________________________



--- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) ---
83 FPS at Intake Valve Curtain Area at .722 Lift
110 FPS at Intake Valve OD Area and at Convergence Lift = .548
136 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 6.102 sq.in. at 7000 RPM
350 FPS Velocity CSA= 2.367 sq.in. at 7000 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 2.513 sq.in. at 7000 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 2.667 sq.in. at 7000 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 2.764 sq.in. at 7000 RPM Recommended Port CSA
285 FPS Velocity CSA= 2.910 sq.in. at 7000 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 3.317 sq.in. at 7000 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 3.686 sq.in. at 7000 RPM Largest Intake Port Entry CSA
200 FPS Velocity CSA= 4.147 sq.in. at 7000 RPM Torque Loss + Reversion


--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) ---
81 FPS at Exhaust Valve Curtain Area at .702 Lift
133 FPS at Exhaust Valve OD Area and at Convergence Lift = .428
165 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 3.720 sq.in. at 7000 RPM
435 FPS Velocity CSA= 1.407 sq.in. at 7000 RPM Sonic Choke at Throat Area
350 FPS Velocity CSA= 1.747 sq.in. at 7000 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 1.855 sq.in. at 7000 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 1.968 sq.in. at 7000 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 2.040 sq.in. at 7000 RPM Recommended Port CSA
285 FPS Velocity CSA= 2.148 sq.in. at 7000 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 2.448 sq.in. at 7000 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 2.720 sq.in. at 7000 RPM Largest Exhaust Port Exit CSA
200 FPS Velocity CSA= 3.060 sq.in. at 7000 RPM Torque Loss + Reversion





Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.050 1010 0.688 0.537 0.399 0.294 49.8 36.8
.075 1514 1.032 0.806 0.598 0.441 74.8 55.2
.100 2019 1.376 1.074 0.797 0.589 99.7 73.6
.125 2524 1.720 1.343 0.997 0.736 124.6 92.0
.150 3029 2.064 1.612 1.196 0.883 149.5 110.4
.175 3534 2.408 1.880 1.396 1.030 174.5 128.8
.200 4039 2.752 2.149 1.595 1.177 199.4 147.1
.225 4543 3.096 2.417 1.794 1.324 224.3 165.5
.250 5048 3.440 2.686 1.994 1.471 249.2 183.9
.275 5553 3.784 2.955 2.193 1.619 274.1 202.3
.300 6058 4.128 3.223 2.392 1.766 299.1 220.7
.325 6563 4.472 3.492 2.592 1.913 324.0 239.1
.350 7068 4.816 3.760 2.791 2.060 348.9 257.5
.375 7572 5.160 4.029 2.991 2.207 373.8 275.9
.400 8077 5.504 4.298 3.190 2.354 398.7 294.3

Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.425 8582 5.848 4.566 3.389 2.501 423.7 312.7
.450 9087 6.192 4.835 3.589 2.649 448.6 331.1
.475 9592 6.536 5.104 3.788 2.796 473.5 349.5
.500 10097 6.880 5.372 3.987 2.943 498.4 367.9
.525 10601 7.224 5.641 4.187 3.090 523.4 386.3
.550 11106 7.568 5.909 4.386 3.237 548.3 404.7
.575 11611 7.912 6.178 4.586 3.384 573.2 423.0
.600 12116 8.256 6.447 4.785 3.531 598.1 441.4
.625 12621 8.600 6.715 4.984 3.679 623.0 459.8
.650 13126 8.944 6.984 5.184 3.826 648.0 478.2
.675 13630 9.288 7.252 5.383 3.973 672.9 496.6
.700 14135 9.632 7.521 5.582 4.120 697.8 515.0
.725 14640 9.976 7.790 5.782 4.267 722.7 533.4

[kid vishus]

It is getting full throttle, I have checked numerous times.

I am pretty sure the timing marks in the correct place. I have added timing and it picked up a little, and if I take any away, it slows down.

[RyonPro1]

How new is the combination??
Is the fuel system new? What about the vent in the tank?
Is the vent kinked, or to small?
Just brainstorming.

Shawn

[dbusch]

You have a good bit more in the 60ft department. 108mph should allow approx. 6.35-6.40 ETs. that is still less than 550hp on a Moroso slide rule. an 1 7/8" header can make 650hp pretty easily, so i dont think that is your problem.

are these heads filled in the floors? If not, you have no velocity there. 4v heads will not run unless prepared by someone who is VERY experienced with them. the chambers suck too. i think this may be your biggest crutch. i would put a set of 225cc 3v CHI heads on there in a heartbeat. what are your chamber ccs and what does the piston displace?

what is your fuel system? how much valve spring do you have? have they been checked lately?

what happens if you shift this above 7000 rpm? you certainly should have enough cross section to go there...

your cam is wrong if you have 15.0 compression. A cam like that is good for about 12.5 compression assuming it is at 104 intake centerline. Your timing events are way too far advanced. did you try a cam with wider lobe sep and more exhaust duration? a 15.0 compression 400" mill should be turning 8500+rpm, IMO. when you have the right cam, THEN a larger header will help you, along with your taller (and larger) intake manifold.

[kid vishus]

How new is the combination??
Is the fuel system new? What about the vent in the tank?
Is the vent kinked, or to small?
Just brainstorming.

Shawn

The motor was gone thru this past winter. It did not run any better last year.

Fuel system is not new, it was put on the car about 5 yrs ago.

The vent isnt kinked. It's -8 braided line so I doubt if it's too small.