doctors orders

Discussion in ''Da Nailhead' started by gsgtx, Jul 27, 2010.

  1. telriv

    telriv Founders Club Member

    Low end comes with more initial advance. Top end becomes better when the fully advanced rate comes in at a lower RPM. A trick is to get 36* advance by 25-2700RPM's & have it retard 4* anything above 3800RPM's. My Riv. did a 13.902ET@98MPH. Sixty foots are usually around 1.92-1.98. Your MPH should be closer to low 14's-high 13's.
     
  2. Bigpig455

    Bigpig455 Fastest of the slow....

    Tom - good talking to you yesterday...

    The MPH I'm showing above was measured by a G-Tech meter, so I doubt it's true...

    I ran at Lebanon Valley when the car was dead stock...the meter at that point showed I was running an average of 15.1@94 on the street, I repeatedly ran 15.3@88 on the track, all 60 ft's a hair over 2.2..only difference was I usually run the street early in the morning when the temps are in the 50's or lower, the day at the track was 70-80 degrees.

    I dont doubt the car is faster with the manifold and distributor mods, but I doubt its that much faster, and I'd be willing to bet on the track it would just crack 14's now.

    Rhett
     
  3. Bigpig455

    Bigpig455 Fastest of the slow....

    Backed up my prior best run this AM with a 14.71 @ 98.7, running heavy with fuel and toolbox to help traction - just chirped off the line and hooked...car feels GREAT, especially through the midrange.

    Tom - please tell me more on how you can dial back timing at top end...I was always under the impression that timing is linear - you hit full advance at whatever RPM and stay there for the duration of the pull....is the retardation you're talking about done electronically?
     
  4. doc

    doc Well-Known Member

    :laugh: :laugh: I am lovin it.....:laugh: :laugh:
     
  5. CarlBraun

    CarlBraun Registered Abuser

    Big Pig

    take a look at craigslist....there's a c-load of them there. Better yet...go to craiglook.com and just type in sun distributor and you'll see all of them all over the country. Lots of them for $500-$800 but most dont work or "need adjustment". There is a guy in so cal (costa mesa) that has one thats ready to go but its a little $$$.

    good luck
     
  6. gsgtx

    gsgtx Silver Level contributor

    in an old popular hot rodding book they took a a single 4 intake from a 455 olds and cut the intake like docs mod and dyno it.first they went up one step on the jets and then back to stock the stock jetting. stock jetting was best. heres the test... uncut intake stock jets and cut intake stock jets.the cut one loss 1hp at 1500rpm. loss 1hp at 2000rpm. still 1hp at 2500rpm. then at 3000rpm made 2hp. at 3500rpm made 4hp. at 4000rpm made 1hp.at 4500rpm made 17hp more. at 5000rpm made 23hp more. at 5500rpm made 38hp more. this was with a 850 holley on a offy dual-port 360 manifold,isky cam on a 455 olds motor. hope the way i wrote this is understandable.
     
  7. CameoInvicta

    CameoInvicta Well-Known Member

    Yes sir, very understandable, thanks for posting!!!
     
  8. doc

    doc Well-Known Member

    Hmmmmm,,,,I wonder if any of the guys has done this mod in the ''stock appearing'' classes????? :Do No:
     
  9. wkillgs

    wkillgs Gold Level Contributor

  10. telriv

    telriv Founders Club Member

    This is not an attempt to "knock" Doc's intake mods at all. What I have found is that cutting out the dividers on both the upper & lower plenums hurts the bottom end & improves the mid, somewhat, but really helps the top end. What I do & have found very beneficial is to just cut out the divider on the upper plenum ONLY. Then I take & radius the heck out of the bottom of the holes. If you stick your finger down there you will find that the factory did a "little" bit of radiusing at this point. What I do is radius it even more, much more. Then on a single 4 intake raise the roof of the manifold on #3 cylinder where it enters the head as much as you feel comfortable with. Don't just smooth it out, raise it. At the point your raising you can feel the thickness. Number 3 is the worst flowing & is the port that is shortest in length. Doing the mod this way does NOT seem to affect the bottom end at all & improves the top end breathing also. Maybe not as much top end as Doc's mod but then again the bottom is not lost. On our usually heavy cars we cannot afford to lose ANY bottom end. Just my thoughts.

    Tom T.
     
  11. funkyriv

    funkyriv Well-Known Member

    wow, the intake in the example is totally opened up to dual plane design. seems like a high RPM application that would hurt bottom end (???)
     

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  12. gsgtx

    gsgtx Silver Level contributor

    the olds intake they cut side
    to side not front to back like we do . maybe because of that intake its a 360 design its like a dual and a single plane together
     
  13. doc

    doc Well-Known Member

    i do not cut the center divider out like that ,,, it would destroy the torque.... i run holley 3 bbl carbs on my cars so I raise the carb up with a spacer to clear the secondary plate.... the plate matches the carb base plate.... not the intake manifold.....
     
  14. gsgtx

    gsgtx Silver Level contributor

    they left the divider too but going the other way you have the front prim both open then a divider then secd are open
     
  15. gsgtx

    gsgtx Silver Level contributor

    this was back in 1977 they never gave the torque readings just horsepower.
     
  16. gsgtx

    gsgtx Silver Level contributor

    i asked gessler about that and thats why he leaves the divider there just what doc says too
     
  17. kitabel

    kitabel Well-Known Member

    Dual-plane manifolds are always separated left & right, which is why they need big CFM: each cylinder only gets 1/2 of the CFM. When you reduce or remove the divider, you make a bad single-plane out of it (joining all 8 cylinders), but top end goes up. Joining both primaries and both secondaries is not a plan, but a ruined manifold.

    the secondaries are dumping open too soon, but with out permanent mods I dont think I can change that on an AFB
    That's your bog, right there. The secondary air doors are opening too soon. They're counter-weighted, and changing when they open involves adding or removing "ballast" from the door itself.

    offy dual-port 360 manifold
    Offenhauser makes a 360 manifold, which is a divided plenum but split left and right bank 1+3+5+7 and 2+4+6+8 (rather than 2 cylinders from each, like a dual-plane: 2+3+5+8 and 1+4+6+7).
    Offenhauser makes a Dual-Port manifold, which is 2 single-plane manifolds one on top of the other. The primaries feed 1, the secondaries feed the other.
    They don't make a dual-port 360 manifold.
     
  18. gsgtx

    gsgtx Silver Level contributor

    they wrote quote, offy dual-port 360 manifold. could be a misprint
     
  19. kitabel

    kitabel Well-Known Member

    The 360 is their normal model, I'm not sure they made a Dual-Port for Buick. They look weird - the top is nearly flat (like a non high-rise single plane), and the individual port runners are divided horizontally top & bottom at the flange.

    If you've made sure the primary to secondary linkage is correct (not opening simultaneous with the primary), is the link to the 2nd carb simultaneous or progressive? Progressive gives slightly worse mixture distribution but sometimes helps response.
    If it is already, with the engine warm blip the throttle and see if the rear air doors open - they should only crack slightly. If they open fully, weight them down by clipping lead split-shot (fishing sinker) on the door edges. If they don't move no matter what you have to trim some weight off.
     
  20. kitabel

    kitabel Well-Known Member

    I raise the carb up with a spacer to clear the secondary plate.... the plate matches the carb base plate.... not the intake manifold.....

    But... the left and right sides are still connected in the adapter. Just a guess: the minimum cross-over is 7/8" 1-3/4" or 1.53 square inches.
     

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