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Thread: question on timing and carb size.
          
   
   

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  1. #1
    tweaked250r is offline CHR Member Visit my Photo Gallery
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    Car Year, Make, Model: 84 stepper
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    question on timing and carb size.

     



    I just got my rebuilt motor running and I have some questions about the timing and carb. My motor goes as follows...

    355 sbc
    flat tops (about 10:1)
    edelbrock performer RPM aluminum heads
    Lunati cam 227/234 duration at .050 490/504 lift, 110 lobe seperation
    magnum rockers
    stays at about 185-190 degrees temp wise.
    750 holley, vacume
    Accel distributor

    My first question is when I went to set the initial timing I took the vacume line off the distributor and set it to about 10 degrees advanced. I hooked the vacume back up and it went up to about 18 still at idle. Is this right?? I dont know if its supposed to advance right off idle that much?? Also for my set up what do you guys recommend for total all in timing?... When I nail the throttle it hesitates first then revs up. A 750 is to big for my set up correct? Will a smaller carb make it more snappy? I will do ANYTHING you guys tell me to, to make this run a little better and get it figured out. Thanks for the help
    when in dout, throttle out

  2. #2
    Dave Severson is offline CHR Member/Contributor Visit my Photo Gallery
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    Car Year, Make, Model: '67 Ranchero, '57 Chevy, '82 Camaro,
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    Looks like a 600 CFM would be just about right, and yes throttle response would most likely improve. Might want to try your initial timing at 8 to 10 degrees and all the timing in by 2200 to 2500 RPM with total advance around 32 to 34 degrees. Should give you a good baseline to tune from. Watch for detonation closely, then do some plug reading and jetting corrections on the carb. I'm really getting spoiled, after the initial run-in I do my tuning on a chassis dyno. Takes all the guesswork and trial and error out of it....
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  3. #3
    S19243H's Avatar
    S19243H is offline CHR Member Visit my Photo Gallery
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    Car Year, Make, Model: 23 t bucket
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    hi tweaked250r, i also installed the same cam in my 350,it has 9.0:1compression,600 eldebrock,performer rpm intake,runs like a bear. im going through this timing issue also, my problem is if i set mine any were near 10 btdc i cant get close to 34 total, right now i have 20 initial and 34 tota;my question to you is were are you idling at without a load and in gear ? are you running a auto? do you have a stall converter? what size? i drop about 400 rpms from park to in gear so i still have some playing around to do , i believe youre talking about the lunati voodoo cam thats a awsom cam, i use ported vacuum on mine
    GLENN
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  4. #4
    Steve M is offline CHR Member Visit my Photo Gallery
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    On the hesitation:
    1. With the engine off look down the primary side and move the throttle lever. You should see fuel dumped in the bores by the accelerator pump. If not, find out what is plugging the system.
    2. Insure that there is NO play between the accel. pump arm and the lever on the carb. linkage. There is a screw with a spring there to adjust if needed.
    3. Check the plastic cam on the carb linkage that moves the linkage for the accel. pump. It should give movemement right away. If it does not there is a second set of holes in the cam to move to another position or you could buy a set of cams to cover about any situation real cheap. Stick with the stock cam profile or real close to it to avoid causing other isssues.
    4. If you still have a hesitation then switch to larger squirters. Those are the tubes that dump the fuel into the throttle bores.

    Your timing sounds about right with the advice given by the 2 gentlemen above.

  5. #5
    tweaked250r is offline CHR Member Visit my Photo Gallery
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    ok, I took the 750 off and put my old edelbrock 600 on. MAJOR diffrence in throttle responce. I think their might have been a problem with the holley, but anyways thier is no hessitation in park however, going down the road at any RPM under 3,500 when I go wide open it kind of stumbles and the rpm goes down about 500 RPM for about a half of a second then it picks up and starts to scream. My freinds car does the same thing with the same carb also. Iv tryed advancing the timing but it doesnt really make a big diffrence. Do any of you have an idea as to what that could be? I appriciate the help alot.


    S19243H..... I would make sure your idle is at ABOUT 800 rpm in park first thing. Second take a vacume guage and hook it up to where ur distributor is getting its vacume. There should be VERY LITTLE to NO vacume at idle, if thier is then its the wrong port on the carb. With my truck it idles about 800RPM and in gear goes to about 600. I have a 2500 stall.
    when in dout, throttle out

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