cylinder heads and superchargers

[Dave Severson]

Doing a bit of studying, with a centrifugal type supercharger operating at about 11 lbs. boost in a drag engine, AFR recomends a 205 intake runner, and a cnc'd 73 exhaust port with a 58cc chamber for an engine in the 3500 to 8,000 rpm level.... I'm calculating for street use, 9 lbs of boost a 185 intake with the 73 exhaust, 58 chamber and shifting out at 6500 rpm would be close to correct????? I do know the centrifugal blowers don't like restriction on either the hot or cold side of the combustion chamber.... Just wondering if you engine guys thought I was at least close on a head.... Oh yeah, 408 cubes, EFI, 2500 pound car with a 5 speed.... AFR calls the head an Outlaw Street head, part #1406----but doesn't have anything on the exhaust port rework for the supercharger..... Also looked at a similar Trick Flow head, close to the same specs including the 8mm valves and .600 lift springs, etc.



OK, so AFR explains it waaaaaay better then I do:

Quote from AFR data--

Outlaw heads for the street or strip from AFR!
These AFR SBF Street/Strip Outlaw aluminum cylinder heads come ready for maximum small block Ford performance. They are not emissions legal. The 165cc heads come with lightweight 8mm, 1.900 in. intake and 1.600 in. exhaust valves and the 185cc version sports 8mm, 2.020 in. intake and 1.600 in. exhaust valves. Both cylinder heads feature 58cc or 68cc combustion chambers with 68cc exhaust ports. Both the 165cc and 185cc heads have an available nitrous or blower exhaust port option featuring a 70cc ultra high-flowing exhaust port. With AFR's trademark 3/4 in. thick head deck, it's no problem handling that additional cylinder pressure. Each of these serious race pieces in street disguises is also drilled for the larger 1/2 in. head bolt hole as a standard feature for maximum head gasket retention.

[techinspector1]

Playin' with the DynoSim, here's the best I could do using your limit of 9 psi.
Ford 408 Windsor
AFR185/73 2.02/1.60
9.0:1 SCR
1100 CFM (limit of my software) My calculations say you will need 1400 CFM @ 9 psi @ 7500 rpm's @ sea level.
Paxton Novi 2000 @ 9psi
90% efficiency intercooler
CompCams 35-770-8 Solid Street Roller
274/280/, 236/242, 0.602"/0.608", 110. Timing specs @ 0.050" are:12/44/55/7
RPM HP TQ
2000 223 585
2500 299 629
3000 376 659
3500 457 686
4000 530 696
4500 600 700
5000 658 692
5500 692 661
6000 723 633
6500 718 580
7000 691 518
7500 627 439

I was playin with it like I said and when I first used the Novi 2000, the torque jumped up to 850 @ 2000. I said wow. Then when I played with it and changed some things around, I never could get that power back. I don't know if there is a glitch in the software or what. I also checked the Paxton SN2000, Vortech V1-A, V1-B, V2-S, V3-J, V3-R, V3-S and V4-T. Novi 2000 showed the best numbers. Anyway, this is the optimum I could get with changing things around within reason. Intercooler efficiencies ran between 10% and 150%, so I kept dialing in intercooler until I got 700 ft./lbs of torque after I got the cam zeroed in.

Just read your other PM about the 10.5:1 SCR, so went back and plugged that in. Made good power with the same cam, but I figured more cam would show up a little better with the increased SCR. Changed to Comp 35-771-8 and got 800 hp @ 6500 and 735 ft/lbs @ 5000 with 9 lbs of boost. Cam specs 280/286, 242/248, 0.608"/0.614", 110. Timing specs @ 0.050" are: 15/47/58/10. Peak volumetric efficiency with this combo is 136.6% @ 6000 and peak BMEP is 271.5 @ 5000. Effective static compression ratio with 10.5 SCR and 9 lbs of boost will be 16.9:1. Effective with 9.0:1 and 9 lbs will be 14.5:1.

Novi 2000 specs for this test are:
Island Flow- 775.0 CFM
Impeller Speed- 41000 rpm's
Peak Efficiency- 70%
Belt Ratio- 1.0
Pressure Ratio- 2.20
Internal Ratio- 3.54

Aw heck, I'll just go ahead and chart out the whole thing......
RPM HP TQ VE BMEP
2000 226 592 93 218
2500 305 640 103 236
3000 383 671 112 247
3500 471 706 120 260
4000 551 724 126 267
4500 628 733 130 270
5000 700 735 134 271
5500 745 711 135 262
6000 784 686 136 253
6500 800 647 135 238
7000 796 598 133 220
7500 747 523 126 193
8000 683 449 119 165

[Dave Severson]

Thanks so Much, Richard!!!

What I find most amazing on the numbers is how flat the torque remains.... Certainly does make the small engine think it's a whole lot bigger!!!! Would definitely require the aftermarket block with the two extra head bolts per side for any extended street use, don't you think????

Also extremely interesting that the Novi showed to be the best.... Certainly isn't the most exspensive of the lot!!!!!

Even being a virtual dyno, as compared to other engine performance calculations that you've ran on it, comparatively to them it is certainly the right way to go, don't you think???

Again, thanks a ton, Richard....

[Dave Severson]

Richard, I printed this and saved it in the 'puter....shouldn't lose this one!!!! Thanks again!!!!

[techinspector1]

Yeah, not bad. And that was with 185/73 heads. I'll play with it some more with 205/73 heads and also try 112 and 114 lobe separation angles. Blower Drive Service uses 110 for gasoline, 112-114 for alcohol. I would feel confident about E85 supporting 14.5:1 effective, but I'm not so sure about supporting 16.9:1. Do you have reliable figures that show support at that level? Just for grins, I went to the Keith Black DCR calculator. At 16.9 effective with the 35-771-8 cam, DCR is a whopping 13.61:1

[techinspector1]

Everything the same except swapped to humongous heads and lowered SCR.
AFR 225/80 2.08"/1.60"
SCR 9.5:1, effective SCR @ 9 lbs 15.35:1
Fuel E85

RPM HP TQ VE BMEP
2000 214 563 91 210
2500 291 612 101 229
3000 369 647 110 242
3500 457 685 118 256
4000 541 710 125 266
4500 621 725 130 271
5000 699 734 135 275
5500 753 719 137 269
6000 806 705 139 264
6500 836 676 139 253
7000 850 637 138 238
7500 828 580 133 217
8000 775 509 126 190

So, peak torque remained the same but we picked up 50 hp with less SCR and a little cushion on the effective SCR. Torque did fall off under 5000 as would be expected with bigger heads.

Will play some more later. Will have to customize a cam on my calculator. Can't find one with this much timing that is ground on 112 or 114 from a stock cam catalog.

[Dave Severson]

hmmm. the bigger heads had some surprising results.... sort of..... The best running normally aspirated SBF's we've raced before going to BBF's had the same torque issues... Made the torque band a bit narrower which is not really an issue with a 5 speed at the track, but certainly becomes one on the street....Not always "acceptable" to keep the revs above 5,000 when uptown on Saturday night playing with the guys!!!!!! Or so they tell me....

[techinspector1]

What's that Bunkie, you want more torque? Well, how does 600 ft/lbs @ 1800 grab ya'? YEAH BABY, with the torque peak at 4000.
SCR 10.0:1, effective SCR 16.1:1 @ 9 lbs.
Comp Solid Street Roller #35-769-8, 268/274, 236/236, 0.589"/0.602", 106/114/110, timing at 0.050" 12/44/52/4, advanced 2 degrees from these figures.
AFR 205/73, 2.08"/1.60"

RPM HP TQ VE BMEP
2000 238 625 97 234
2500 318 669 106 250
3000 401 702 114 262
3500 487 731 122 273
4000 566 743 127 278
4500 636 743 130 278
5000 699 734 132 275
5500 742 709 133 265
6000 768 672 132 251
6500 769 621 129 232
7000 749 562 124 210
7500 688 482 116 180

I tried some wider LSA's, but the motor didn't like them. Works best on 110. This shorter cam goes over the horsepower hump at 6500, but you have to live with that if you're gonna make the torque this combo does. (600+ ft/lbs from 1800 to 6700). This motor will need 1235 CFM @ 6500. Between the chamber, gasket, piston deck height and piston crown, you'll need to come up with 91.6 cc's to make the 10.0:1 SCR.

[Dave Severson]

Amazing.... The torque stays above 700 from 3000 to 5500 and would still be at 670 at 6,000 rpm. Shift at 6000 and catch the next gear still above 700!!!!!!!!! Now with a 5 speed with 5th at 1:1.............. Hmmmmm, better get my dual disc freshened up, huh?????

Actually, the McCleod Soft Lok single disc would be a whole lot easier on things.... especially during the 5500 RPM launch...... Way big fun, anyway!!!!!!!

Better get some sleep so I can get up in the morning and start making some extra $$$$$$!!!!!!!!!!!!!