74 Z28 engine rebuild time

Discussion in 'Engine Topic' started by younda, Jan 15, 2018.

  1. Rich Schmidt

    Rich Schmidt Veteran Member

    4,215
    30
    Mar 27, 2010
    Denville NJ
    Use the stock block and heads. BUy a lower priced internally balanced 383 stroker kit. Have the stock heads rebuilt with a 3 angle valve job and back cut on the valves. A bowl blend and reshaping the short turn on the heads would help but that is up to you. A hydraulic roller cam would help with durability. I would go with something in the mid 220's at .050 on the intake lobe with about .500" lift at the valve with a 112 or 114 lobe separation angle and 110 intake centerline. Have the Qjet rebuilt by an expert shop that can actually calibrate it rather than just rebuilt it.
     
  2. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

    14,377
    253
    Mar 25, 1999
    San Jose, CA, USA
    A few of big questions here:
    1. What is your budget? Probably the most important question of them all
    2. How committed are you to staying original? Is a full crate motor an option
    3. What transmission and rear gears are you running?
    4. You are saying you want to stay with factory exhaust manifold or intake manifold, why? They both really flow poorly and will be a barrier to making decent power.
     
  3. younda

    younda Member

    99
    23
    Jun 26, 2015
    MA USA
    Responders- I very much appreciate the several responses to my post and went with a stock rebuild and will be getting the engine back this week. Also getting a numbers matching quadrajet rebuilt (found through this site) to put on top.
     
    Last edited: Mar 3, 2018
  4. secondgenaddict

    secondgenaddict Veteran Member

    159
    19
    Dec 29, 2012
    Upstate South Carolina
    Size your camshaft to the intake runner volume and how much the HEADs flow... this is the most important consideration...
    I have custom CROWER CAMS designed by Dave Crower and without flow numbers every .100 from .100 - .700 he doesn't want to do it...why? He flat out told me that it is guessing in the dark without them and he is afraid the customer will not be satisfied.
    The idea is to keep velocity high, because it increases your volumetric efficiency, high velocities allow more overlap and closing the intake later - high exhaust velocity with overlap allows the escaping exhaust to create a vacuum in the cylinder which pulls the intake charge - high velocity in the intake runners allow the intake valve to stay open past bottom dead center and allow the column of air to pack the cylinder even after the piston has begun it's compression stroke.
    FWIW I provide Crower everything, weight, rear gear ratio, trans ratios -trans type, compression ratio -tire height - and flow numbers on the heads...
    The last DZ 302 made 350 ft lbs by 2800 rpm and over 500 HP at 7200. 12:1 pistons with stock 186 heads with 2.05 intakes and blending in the bowls & smoothed the transitions into the valves seats. THE CAM was 630 gross lift 112 lobe separation - duration was dual pattern with approx 268 intake 280 exhaust.
     

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