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Low rwhp?

Discussion in 'Dyno Figures' started by Joeseb87, Sep 11, 2016.

  1. Joeseb87

    Joeseb87 New Member

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    Newly built 355 stroker, l34 heads equivalent 670 vac secondary carb, very mild cam 214/ 214 @ .50, zero decked 10.1 to 1 compression had it dynotuned and got a print out of 152.5 RWKW does this seem low
     
  2. EYY

    EYY Well-Known Member

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    What manifold are you using and what are torque figures? I'd expect 180-210 rwkw with the banana manifold for your combo, so with a hywinder or harrop I'd expect around the 220-240 mark.
     
  3. gtrboyy

    gtrboyy Well-Known Member

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    It's early heads not symetrical efi.

    Smallish cam,early heads,dual plane & moderate carby size with 355 cubes wouldnt be expecting much hp but good torque.

    Probably needs more cam to match the 355 cubes & 10:1 cr

    More importantly how does it go/drive?

    Assuming it's got tall gearing & small. stally
     
  4. EYY

    EYY Well-Known Member

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    Ah of course. Are they proper l34 heads, or are they late vk/stock vl heads? You can tell by the type of exhaust crossover (single bolt or two bolts diagonally across from one another in the middle of each head for the manifold)

    The heads, ignition timing (what dizzy are you using - genuine Bosch? Has it been regraphed? How much mechanical advance? Initial?), jetting and mild cam will be the problems as mentioned by gtrboy.

    Heads, compression and cam are the most important things. Most stock intakes are alright (especially the pre pollution manifolds) and the stock quadrajet is more than adequate. With that cam a dual plane manifold will be well suited as it won't make power above 5500 or so.
     
  5. gtrboyy

    gtrboyy Well-Known Member

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    l34 type heads is ol' slang for bigger valves...kinda like stage 5 cam brah

    It's probably just strangled top end strangling the 355/10:1 cr bottom end.
     
  6. EYY

    EYY Well-Known Member

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    Yeah if they're late pollution heads they have the l34 sized valves as standard, but the porting isn't anything special and the crossover heats up the manifold which doesn't help performance lol

    Another question. What valve springs were fitted?

    Tbh on a 308 a cam with 214 @.050 isn't even noticeable in terms of driveability and manners - I have one with similar specs in mine. I'd pull the cam out and fit something with 230@.050 and .500 lift like a 286. Would get away without a converter too if it's just a streeter in a 355.
     
  7. Joeseb87

    Joeseb87 New Member

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    It's got a dual plane edelbrock performer manifold, msd pro billet dizzy, blaster 3 coil, 12 degree initial 30 total timing
     
    Last edited: Sep 12, 2016
  8. Joeseb87

    Joeseb87 New Member

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    501nm of torque 3.36 gearing stock converter, also if I do the maths and multiply the tourqe x revs divided by 5252 it tells me it should be 210kw at the wheels am I wrong in doing this calculation or is the Dyno report wrong
     
    Last edited: Sep 12, 2016
  9. Deuce

    Deuce Super Stock

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    Torque x Revs / 5252 is for HP from lb-ft.
    Metric calculation is different.
     
  10. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    kW = Torque (Nm) x Speed (RPM) / 9548.

    Your figure calculates back to 2200rpm, the above formula then equates to 115 rwkw, so 152 rwhp is about right.
     
  11. Joeseb87

    Joeseb87 New Member

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    So the print out shows rpm 4550, torque at 4550 Rpm is 438 nm
    So 438 x 4550 / 9548 is 208.7 kW
    Or am I understanding the torque wrong

    When I did the 5252 calculation I converted nm to ft lb and then converted the Hp to kW
     
  12. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Didn't you say you had 501 nm of torque though?

    I calculated back from your torque and hp figures and it came out at 2200rpm. 501 nm at 2200rpm is 152hp/115kw.

    You can't pick a random point on the graph and calculate it from there, you need the peak torque figure and the rpm at which that occurs, not the power. You can't pick the peak power rpm and use the torque figure from that point.

    Probably best if you post the readout so we have a better understanding of the graph.
     
  13. Joeseb87

    Joeseb87 New Member

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    Ok so that's where I went wrong I used the torque from the peak power not the maximum torque rpm thanks
     

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