Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Desk top dyno #s

Discussion in 'The Garage' started by Diesel Dan, Mar 15, 2006.

  1. Diesel Dan

    Diesel Dan 1/2 ton status

    Joined:
    Feb 27, 2002
    Posts:
    798
    Likes Received:
    0
    Location:
    Warren, Ohio
    Well just dropped off the 383 at they machine shop and will run it on the dyno tommorrow night.
    Who can run some desk top #s and see how they compare to the actual #s.
    Specs:
    Bore/stroke: 4.030/3.75"
    CR: ~10:1, Keith Black hyperutectics, small dish.
    5.700" rods
    Vortec heads, stock ports, 1.94/1.50" valves
    Cam: GM roller "hot cam", .525" lift, duration@.050 218/228, 1.6 roller rockers
    Intake: performer RPM air gap
    Carb: Holley model, O-80508S, 750 CFM, dual feed, vacuum secondaries.
    Hedman headers with stepped primaries and 3" collectors, don't know primary sizes but would guess initial size 1 5/8" stepped to 1 3/4. Forgot to measure them.

    Any guesses on HP/TQ?
     
  2. mtnman210

    mtnman210 1/2 ton status

    Joined:
    May 30, 2003
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Northridge, Ca
  3. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    I'd run that again with the same cam specs, but change it to hydraulic flat tappet. In others experience (look at it yourself before/after) the roller cam selection alone, even if the cam specs otherwise aren't changed, changes the numbers way too much.

    Also, the Vortec head files (.flw?) are pretty easily available on the web...I think you can download the whole set he has here:
    http://www.chevyasylum.com/dyno2000/Welcome.html
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

    Joined:
    Mar 22, 2002
    Posts:
    6,587
    Likes Received:
    0
    Location:
    Sheridan, Michigan
  5. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    Cam specs don't jive between first and second do they? Yours are seat to seat, the other is at .050.
     
  6. big83chevy4x4

    big83chevy4x4 3/4 ton status

    Joined:
    Mar 22, 2002
    Posts:
    6,587
    Likes Received:
    0
    Location:
    Sheridan, Michigan
    i couldn't find the specific IVO IVC EVO EVC numbers, so i had to look up the .006 duration and put it in. the .050 duration comes out real close to the 218/228
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    Now I'm kind of curious to see what the first one would look like with JUST the .flw for the Vortecs! Some serious differences for sure, but with hydraulic flat tappet AND the Vortec .flw plugged in, a bit difficult to discern what is making what difference.

    But if your cam numbers are pretty close, my guess is they are within 10% of the dyno.

    Don't forget, dyno numbers are also not exacts, two dyno's won't read the same, so even there you've got some "fudge factor" built in.
     
  8. big83chevy4x4

    big83chevy4x4 3/4 ton status

    Joined:
    Mar 22, 2002
    Posts:
    6,587
    Likes Received:
    0
    Location:
    Sheridan, Michigan
    i got to looking at mtnman's pic, the cam is not the cam that dan used, mtnman used a 278/278 duration with 108 lobe center and the GMP hotcam has a 272/281 duration with a 112 lobe center. i think thats the big reason the graphs are different.

    here is the same motor with a set of 441 heads
    http://img.photobucket.com/albums/v299/big83chevy4x4/DD2.jpg
     
  9. Diesel Dan

    Diesel Dan 1/2 ton status

    Joined:
    Feb 27, 2002
    Posts:
    798
    Likes Received:
    0
    Location:
    Warren, Ohio
    Ok, it was a long night.
    Took longer than we thought to hook everything up and get going. Don't have the graphs yet but here are the basic #s.
    It is a solid 375hp/410tq.
    More to be had out of the carb, running on the lean side. Could use better plugs, broke it in on champion plugs and they seen almost 20hp on the last hot 383 by switching to autolights. This is the setup that will be in the blazer so they are closer to real world #s instead of max dyno #s. Could have used their large tube headers with 3.5" exhuast but went with the truck headers and 2.5" to simulate the truck setup.

    Really smooth power curve. Max HP 52-5400, just slightly dropping off to 6000. TQ was over 400 as early as 3000 IIRC. Tried a 2000 RPM pull and that was interesting, first time they tried it that low. Loaded the dyno ~2K, which was somewhat tricky and hit the go button and the rpm didn't climb much for a while, no bogging, but tq just kept climbing. IIRC, 330+ @2500rpm. He pumped the throttle slightly a couple of times and the added fuel made it come to life so fast he almost hit the E-stop because he thought the dyno broke!

    End result:
    Little less hp than hoping for but will be a really good driveable truck motor.
    Also 750 cfm carb not needed. We never seen cfm figures higher than 550 even at 6000 rpm.
     
  10. mtnman210

    mtnman210 1/2 ton status

    Joined:
    May 30, 2003
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Northridge, Ca
    Sounds like a nice stout motor. And The numbers are pretty good. Have you driven the truck with the new motor yet?
     
  11. Diesel Dan

    Diesel Dan 1/2 ton status

    Joined:
    Feb 27, 2002
    Posts:
    798
    Likes Received:
    0
    Location:
    Warren, Ohio
    Haven't installed the motor, actually haven't even brought it home yet. It is going in a guys '90 blazer. I'll be removing the TBI and using the stock in tank pump with a holley by-pass regulator to feed it. Around that time the guy wants me to install a roll cage and I'm looking at a s&w cage for that.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    To bring this back from the dead, did you ever get a copy of the dyno sheets, and how do they compare to the last Desktop Dyno curves? (http://img.photobucket.com/albums/v299/big83chevy4x4/DD1.jpg)

    Numbers-wise DD was pretty much dead on, I'd say well within the tolerances of two different dynos, which again seems to prove that as long as you feed it good data, desktop dyno is not only valuable to get an approximate idea of what engine changes work or don't work, but also to get a pretty good idea of what the actual power output will be...
     

Share This Page