Is my car running what it should? Engine build thoughts?

Discussion in 'High Performance Modifications' started by Jhboy10, Sep 14, 2020.

  1. G72Zed

    G72Zed Veteran Member

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    Lots of good advise so far for how to improve things, everyone can have a different take on things. This is what I see.

    Assuming starting line weight @ 3550#, it would mean that your making approx. 310hp at the crank, or 250 RWHP. In saying that, it would mean your ET should be in the 13.35 to 13.60 range to correlate with that weight and MPH.

    Taking a shot at doing the math, it would indicate your crossing the line at approx. 4,400 RPM (4,250 w/3% conv. slip)

    Your overall first gear ratio is 8.28, and that's hurting your 60ft big time. The 383 ci is taxing that intake, and your under carb'd as it is.

    Do you have, or do you know your fuel pressure crossing the line?

    A change to a 4.10 gear with those tires will help out big time in the ET dept., but will not make much change in the MPH dept. as your HP will not have changed.

    As noted from others, this should be a mid to high 12 sec. car. Cylinder head also may be getting into choke due to design, has nothing to do with CFM/CC's.
     
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  2. xten

    xten Veteran Member

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    As mentioned above, intake, carb, and tuning. I am a firm believer in a GOOD converter. By that, I mean not an off the shelf out of the box and stick it in converter. I ordered a Coan. They want all the info you can give them, basically everything but a DNA sample. They built it tight, since I was spraying it at the time. Flash was 35-3800 RPM. Last time I grenaded a tranny, I sent the converter back to Coan to get cut open and checked, I told them to loosen it up since I wasn't spraying it anymore at the track. It now flashes at around 4200 RPM and 60's went down with no other changes, and it has perfect street manors.Kid has s 1st gen with a 5,500 PTC converter he runs on the street, same deal.Get a converter built for your car, not one off the shelf, and don't be afraid of a higher stall.That's what instantly gets you into your power band, and with everyday driving you won't even know it's there till you pin it if it's built right.
     
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  3. Jhboy10

    Jhboy10 New Member

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    Thanks for all the advice y'all. I'm gonna start with an intake and bringing my timing back and see how that does. I think I can borrow a 750 too.
     
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  4. carhead22000

    carhead22000 oldblue

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    don't know how tall your rear tires are but taller tires look good but eat up gear ratio.my 383 years ago was not performing right and i went back to a smaller rear tire and car was night and day. Like said intake airgap.fits i have one with low profile air cleaner. I ran a 750 elderbrock .383 liked it.not the best for all out racing but streetability you cant beat them.
     
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  5. JD Muffler

    JD Muffler New Member

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    If I have this right his 1st. gear ratio is 2.48 in the turbo 400. + rear gear is 3.42 . Thus making hi SLR 5.90. By adding to 411's your gonna be at 6.59. maybe 2-3 tenths faster. I went from 456's to 342's and lost about 1 1/2 tenths in the 1/8th.
     
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  6. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    It is not possible to answer your question without defining these things:
    How fast do you want to go?
    What is our definition of streetable?

    I had a 1973 RS in 1991. Drove 45 miles each way to the track.
    Ran 11.80 @ 113 through the muffs.
    383 pump gas.
    3500# with me in it.
     
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  7. G72Zed

    G72Zed Veteran Member

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    SLR is actually calculated by multiplying the trans gear with the rear gear. So in this case, the SLR would be 8.48 for the 3.73's and a more sought after 10.19 for the jump to a 4.11 rear gear.
     
  8. G72Zed

    G72Zed Veteran Member

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    Nice ET & MPH, any chance you had the engine dyno'd ?

    My WAG, based on weight/MPH would be around 390hp at the wheels and approx. 450-475HP at the flywheel.
     
  9. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    450 HP at 6200, 480 torque. This was on an accurate dyno by someone who knew what they were doing.
     
  10. biker

    biker Veteran Member

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    Any chance you remember what the cam specs were for that engine?
     

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