Is bigger better?

Discussion in 'Engine Topic' started by Kskevin, Feb 16, 2019.

  1. Kskevin

    Kskevin Member

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    So my buddy and me both have 78 z28. Both have th350 with 2500 stall and 3.43 rear gears. We are pretty much having a build off. We both have 357 with Hypereutectic flat top pistons. Both going to be running an Edelbrock high rise air gap intake with Holley 750 carb and headers. Both running hyd roller cams and full roller rockers. Now we're we are not seeing eye to eye is heads and cams. I'm looking at 183 cc aluminum CNC ported heads with lunatii voodoo cam.
    • Advertised Duration (Int/Exh): 270/278
    • Duration @ .050 (Int/Exh): 219/227
    • Gross Valve Lift (Int/Exh): .515/.530
    • LSA/ICL: 112/106
    • Valve Lash (Int/Exh): Hyd/Hyd
    • RPM Range: 1800-6000. Now he wants to run 200cc aluminum CNC ported heads with lunatii voodoo cam
      • Advertised Duration (Int/Exh): 282/290
      • Duration @ .050 (Int/Exh): 231/239
      • Gross Valve Lift (Int/Exh): .535/.550
      • LSA/ICL: 110/106
      • Valve Lash (Int/Exh): Hyd/Hyd
      • RPM Range: 2400-6400. The big question is who is going to be better off/faster/more drivable? These cars will be street 90% strip 10%.
     
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  2. 1980RS

    1980RS Veteran Member

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    The first cam will be more streetable with the 180cc heads and will beat the 2nd combo with the 200cc heads, Why? because both cars will have exhaust on them so the gains with the 2nd combo will not show up until you open the headers. Too bad you guys are not up here in MN. I would love to race both of you with my pump gas SB. 358.
     
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  3. Kskevin

    Kskevin Member

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    This is all for fun but so is racing lol we will both be running on pump gas as well. What's your engine specs look like
     
  4. 79RedZ

    79RedZ Veteran Member

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    If I was running that second cam, I would want my converter to have more than 2500 stall. I would want it up in the 3000 rpm range
     
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  5. 1980RS

    1980RS Veteran Member

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    It's a .040 350 4 bolt block, decked with a cast crank, SRP flat top forged pistons on PM rods with ARP bolts
    Cam was a Elgin 1165P hyd .488I .510E 234°I 244°E on a 106 LCA. The other cam I used was a Elgine solid cam and the Comp Cams 292H all 3 ran in the 11's.
    Heads are 034 Mild Ported Bow Tie heads 2.05 1.6 valves with a dual springs, 1.5 Harland Sharp rockers and a stud girdle.
    I have used several intakes that were stock and ported. The last one was a Holley 300-25 Strip Dominator intake.
    Several carbs from a 600 to 850

    Plans are to rebuild the short block as it has over 200 runs on it. I will be putting in a Engle .600 lift roller cam and I will be trying a Holley 300-36 Street Dominator I also will be trying an Eddy Air Gap Dual Planes, both are fully ported. I was just having a little fun with you about racing, always good to see others building SBC these days with the popularity of the LS craze.
     
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  6. Kskevin

    Kskevin Member

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    Everyone loves the LS engines I just like building my sbc. Once I'm done with this one I want to rebuild the 350 that's in it now and go a totally different route probably stroke it and build it for a blower. But no rush I enjoy the time on the engine stand lol
     
  7. G72Zed

    G72Zed Veteran Member

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    Few heads pour over, and allot pour under the advertised CC rating. There may be only 10cc difference between those 2 heads, it's the location of the volume in the runner that's key, be it in the bowl or CSA at the pinch.

    Sometimes a better shaped, larger CC head has the same, or more velocity than a smaller head if attention was paid in the right locations. Chamber shape and size has a big impact also, and not just for compression.

    If the intake has a full divider, it can take more "cam" vs a "cutout or cut down" style. If so, I like the bigger heads and cam, but everyone has there own idea of "street-ability"
     
  8. jeff swisher

    jeff swisher Veteran Member

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    The way I see it is like this The heads will be a big deciding factor. If his 200cc heads have weak runners It will make a turd of his engine..and the smaller runner if it flowed the same amount of air will trump the larger head.

    But if he is on his game and got decent heads I think he will beat you ..I like the larger grind on the cam.
    I really do not like the hypereutectic pistons.

    Something else is who can tune better, and who can make their car stick better.

    I would like to know which heads and compare air flow.
    I know flow on a bench is not everything.
    Just curious. if they flow 235 cfm at .500" lift on the intake side I would be saddened though.
    I would like to see 250+ cfm at .500" and exhaust in the 180 area or I would stick with old GM heads that are home ported.
    Just me though.
     
  9. 73 Z

    73 Z Veteran Member Gold Member

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    My 2 cents, the small cam & head combo will work better and be quicker for a street driver. I just went from a 240+@.50 that came alive at 2500+ rpm to about the same lunati grind you posted 112/110, .227/.231, 530, 180 head. Much more street able, The larger combo is border line strip car. My combo still only makes about 13 psi vac, previous combo was about 9/10.
     
  10. jeff swisher

    jeff swisher Veteran Member

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    Speaking of larger cams and Vacuum.
    I like small heads myself for a dual purpose deal, street/ strip.
    I have ran a single pattern solid flat tappet cam the largest one in a street strip vehicle I had was 252@ .050 and on a 106LSA I ran 1.6 rockers on it for .571 lift ..after lash it was .545".

    Ported HO 305 heads. 1.94-1.60 valves and 175cc runners.
    Hurricane intake and 800 double pumper TH350. 4.11 gears.

    It ran on 91 octane and 36 total timing in a flat top 355" went 11.5's in the 1/4 and pulled 11" vacuum.
    Just enough for power brakes.

    That thing came out of the hole like shooting a rubber band off the end of your finger.
    Summit racing TQ converter that stalled to 3500 and Hoosier dirt track tires on the rear to hook solid to the street.

    I really thought the large duration cam was going to kill the low end and make it feel soggy.
    Just the opposite, that thing revved like a KZ1000 instant throttle response.
    Could be due to the heads having a good port job and small runners.
     
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