383 seems sluggish

Discussion in 'Engine Topic' started by Justin79maro, May 28, 2020.

  1. Justin79maro

    Justin79maro Veteran Member

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    Alright fellas, I’m posting another question so bare with me lol, y’all are so helpful and are basically my performance mentors, I hate spending money and figuring out it’s not what I needed so here’s my question. Current cam is a bootlegger
    232/244 .590/.590 108lsa and I believe a 104cl ? Not sure if that’s right but anyway, the car pulls great down low in first gear it just eats the tires into second but from pulling from about 60 in 2nd in the mid to upper rpms of second gear it just doesn’t have much “go”, my vortec headed 230/236 .510/.520 9.8:1 compression crate 383 from blueprint would smoke this thing from a 60 mph roll, kinda confused on this matter. I’ve emailed the head porter and he just said “lunati cams have lazy lives but it should still pull in the upper rpm” and comp cams suggested deeper gearing. So I wanna know what everyone else thinks. the engine is a factory roller block 385 stroker, it has 195 pro filer aluminum heads ported to 213cc and flow 300cfm @.600 lift, a single plane Motown/bmp intake manifold with a 750cfm Holley, it has 10.5:1 compression, 5.7” rods and the valve springs are set up for my lifters. It’s in a 3600lbs 1979 camaro with a 3,000 stall and 3.42 gears. 1 5/8 headers with manifold gaskets (maybe they block the exhaust port a little?) timing is at 36° total and jets are 70/81. Thank you all for reading this I appreciate it ahead of time
     
  2. Peck

    Peck Veteran Member

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    What rpm are you at in 2nd at 60? It should not be lazy on the top, to be honest with those heads and that cam I would expect you to be saying the exact opposite. However a 213cc head is on the big side for that displacement.
     
  3. Justin79maro

    Justin79maro Veteran Member

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    Around 4000-4500rpm
     
  4. kenny77

    kenny77 Veteran Member Lifetime Gold Member

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    I would think you need to work some with the timing. My ZZ383 took a lot more than I thought . Put down the timing light and play with it by ear and feel
     
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  5. Justin79maro

    Justin79maro Veteran Member

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    Ill try that tomorrow after work
     
  6. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    1 5/8 headers do seem a little small for your setup. I'd see what the timing change does for you...certainly more cost effective.
     
  7. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    I suggest pulling a header and measuring the header primary inside dimension vs. the exhaust port. If the port is obstructed by the header tube, that causes poor performance.
    I always use a 1 3/4" ID primary on a 383. You also mentioned that the heads were "ported". Based on the weight, low stall and gear ratio, I would suggest an RPM air gap intake.
     
  8. G72Zed

    G72Zed Veteran Member

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    Great comments from the others on this, I will add, as the heads get better, you can spread the LSA, also in the same breath, my testing has shown pulling back on the exhaust duration also comes into play with good balanced heads. And when doing this, you generally spread the peaks beyond the ave. 12-1400 RPM.

    To have 590 lift with only 232 @ .050 is not a real lazy lobe, and your at 12* addition duration on the exhaust. I think your over scavenging the mixture in certain RPM's.

    An open plenum intake is carb signal sensitive, combine that with limited gearing, and your out of the "tuning" window quite quickly.

    I have made 540-600 HP on 358-362 SBC with only a 650HP Holley with open plenum intakes, and that Motown you have is a good intake.
     
  9. Justin79maro

    Justin79maro Veteran Member

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    I do have a rpm air gap style intake I can try out if all else fails, what brand of headers do you run?
     
  10. Justin79maro

    Justin79maro Veteran Member

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    So pretty much for it to run best I have to get it super close on the tune?
     

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