Thread: Desktop Dyno?

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Hey guys I have a healthy little small block chevy here, that I know performs very well, as it consistently clicks off low 11 e.t's, and on a perfect day, and a perfect run, pull high 10's on drag radials and open headers. It's been put together for a long time, so a few of the details are probably pretty vague, but I was wondering if somebody around here could run my combo on the "desktop dyno"? it would be really appreciated.

Well anyway, my combo consists of:
a 350 4 bolt main block; bored .060 over
Manley "H Lite" forged 4340 series rods 5.7"
Eagle forged 4340 series crank (factory stroke)
Dome pistons (dont remember specific size or anything, but they are forged aluminum)
Camel Hump "492" over the counter series heads, extensively ported and polished, recut for 2.04(intake)/1.60(exhaust) vaves; I believe they flow 276 cfm (intake)/ and 198 cfm (exhaust) @ .600 lift (the heads were milled and decked to compromise a 12:1 compression ratio when matched with the dome pistons
Manley Valve Springs good for .700 lift
Crane 1.5 full roller rockers
Crane "Saturday Night Special" series Solid Flat Tappet Cam
Here is a direct copy of the cam card from Summit Racings website:

Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 4,600-8,000
Intake Duration at 050 inch Lift: 268
Exhaust Duration at 050 inch Lift: 276
Duration at 050 inch Lift: 268 int./276 exh.
Advertised Intake Duration: 304
Advertised Exhaust Duration: 312
Advertised Duration: 304 int./312 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.572 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.590 in.
Valve Lift with Factory Rocker Arm Ratio: 0.572 int./0.590 exh. lift
Lobe Separation (degrees): 106
Intake Valve Lash: 0.026 in.
Exhaust Valve Lash: 0.026 in.

Weiand "Hi Ram" single quad tunnel ram intake; smoothed runner divider area, ported plenum and ported lower; port matched.
Holley 4150 750 carb; jetted to flow 830 cfm
Hooker Hussler full length 1 3/4" headers 3" collector
and for crusing on the street I've got Flowmaster 3" super 44's dumped right out of the mufflers.

Drivetrain consists of:
a Muncie M22 series 4 speed transmission; pro shifted by Liberty Transmissions; backed by a Zoom Dual Friction Clutch; and the gears are rowed via a Hurst Street Super Shifter
The rearend is a GM 12 Bolt; loaded with a 4.11 posi, and kept to the pavement with Lakewood ladder bars

Rolling stock is Cragar 14x8's on the rear with G60 14 Mickey Thompson Indy Profiles
and Cragar 14x6's on the front with 195x70/14's.

Well I don't know what all is needed for the informative parts of the Desktop Dyno,but I hope I gave enough, if not I'll try to find some old receipts, and my actual head flow #'s somewhere. If I gave too much info, sorry, I'm just really proud of it.

Bowtie,

Your E.T and car weight, trans, tires, etc. should be enough to generate a reasonable estimate of power.

I will enjoy seeing the Computer generated estimate based on your engine build specs vs. the actuall E.T's the car has performed.

Of course the variables can go on and on, track, driver, density altitude, sheer frickin' luck...but interesting to read.

Hope you get some good input here.

Pete

Yeah, I've used those calculators where you enter 1/4 mile E.T; Trap Speed; and Vehicle weight, and I've gotten calculations stating anywhere from 475 at the fly wheel to almost 600 at the flywheel and 475 at the rear wheels.
0I don't know where an actual dyno is around here, and thought that the desktop would give me a pretty good idea if someone is willing to help me out.

Is a desk top dyno worth using / In most of the testing I have seen the desk top over estamates the power so bad it is not even worth looking at . when I built my car i was shooting for high 11.second passes my calculations were that I needed 385 hp . the desk top told me i should have 460 hp . On a real dyno My engine pulled 398 hp. I cut back my shift points and run right on 12 seconds .

I've heard that they sometimes over estimate by a bit, but I was just looking for a ball park figure. I figure that its making around 475ish at the crank, but I'm not real certain.

520.5 H.P 470.2 Torque . To much camshaft for them heads . Better Heads would be your Best Next Step . Are you Spraying it into the 10's ?

Nope. Just a hair under the 11.0 mark with an old school build, and all out hammering on it driving style. Those were the actual numbers off of the desktop? This cam still makes good power with the old 492's but I kind of figured that they were holding me back, I had considered camming it down a little bit with a different Crane Solid Lifter, less lift; duration and a 105 LSA..

Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 4,200-7,200
Intake Duration at 050 inch Lift: 256
Exhaust Duration at 050 inch Lift: 264
Duration at 050 inch Lift: 256 int./264 exh.
Advertised Intake Duration: 292
Advertised Exhaust Duration: 300
Advertised Duration: 292 int./300 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.545 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.563 in.
Valve Lift with Factory Rocker Arm Ratio: 0.545 int./0.563 exh. lift
Lobe Separation (degrees): 105
Intake Valve Lash: 0.026 in.
Exhaust Valve Lash: 0.026 in.

I'm not sure if I would pick up much with it though? Perhaps low end and maybe mid range I would gain a little bit, but it's hard sayin. How do the dyno #'s differ when swapping out the two cams?

529.4 H.P 473.8 Torque .

Those numbers are pretty favorable over what I have now. A swap may be in order. Do you have the chart with peak rpm and all that on your program? I'd be pretty interested to see where the engine would peak with the different cam.

Both cams where near the Same on the H.P 6500's . But the Smaller Cam made it's Peak Torque at 4500's to the Largers 5000 RPM's . If your heads are Ported as You say . This Build could make a Bit more Power at a Little Higher RPM's .

Well with the smaller cam it made more max power? And its torque peaked earlier. I'm pretty satisfied with the ole .572/.590 but it may be worth the swap to the smaller cam, as I've been running this one pretty hard for the last 6 years or so.
And as for the heads I know they were disassembled bare heads when I purchased them from a friend for 100 bucks, and had my local machinist port the hell out of them. Who says you can't make big power with camel humps... I think 500+ horse and 470+ torque is pretty good.

Yes for a 350+60 Over 360ci maybe 12.1 C/R Build that is making Good Power . Your Camshaft Lift is not so High it's that .050 Duration . You get to that Point with Stock casting Heads even ported . That they can only Flow So much . And this is a 360 Not a 383-406 . With 195cc AFR Heads or world Sportsman 200cc and the Bigger Cam the Power will Follow .

Eventually if I ever decide to go all out race with this engine, I'll probably put it in an S10 and build a th350 for it, and go with the aftermarket heads and a bigger cam, but for now I think I'm good with what I have in a 67 Chevelle malibu 4 speed car (makes for A LOT of fun on the street). I appreciate your input though, and thanks for the Desktop data, I was just curious about what kind of numbers I may have. And I may go with the smaller cam before the spring. If I do, I'll post the results I get with it.

Cam it Down some . It will be a More Friendly Car to Drive on the Street and will run just as Strong . But will have more Low end Torque .

I probably will. It's just one of those "If it's not broke don't fix it" kind of things, but "fixing" it may actually help it, ha. I suppose I can talk myself into it, jegs has the cam and lifter kit for 275, I'll probably go that route.