Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

low vacuum

Discussion in 'The Garage' started by 01fatboy, Apr 30, 2003.

  1. 01fatboy

    01fatboy Registered Member

    Joined:
    Apr 25, 2003
    Posts:
    22
    Likes Received:
    0
    Location:
    Virginia
    just installed a rebuilt 350. the norm bored over .30 heads reworked with all new valves and springs edlebrock intake and carb (600). the cam has .480 lift creating low vacuum at idle so coming to a stop at a light can get a little nerving. only getting 12 hg vacuum thinking of getting one of those vacuum reservoirs. mest with the timing and rebuilt the carb nothing inproves it unless I idle it up to 2 grand any other ideas?
     
  2. slimlynn1

    slimlynn1 1/2 ton status

    Joined:
    Apr 9, 2003
    Posts:
    336
    Likes Received:
    0
    Location:
    Hamden, CT
    What are the specs on the cam? What is the initial timing set at, and have you adjusted your carb idle mixture? Ive got a huge solid roller cam and I get about 12 in Hg. at idle. You should be getting more than that. Post some more info.
     
  3. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Bump your timing up to about 16 degrees intial. That should give you about 36 degrees total mechanical if you have an HEI. Then knock the vac advance down to around 12 or so. Please hook it up to ported vacuum too. Worry about the mechanical advance first and just add vac advance to keep mileage and throttle response up.

    I'm not sure how Edelbrock says to set the idle mixutre, as I recall its some elaborate overdone procedure. The simple way is to start ith your idle screws an equal number of turns out and set a baseline idle speed. Say like 750 rpm. Make sure its in gear while you're doing all the settings. Then with your vacuum gauge hooked up to full manifold vacuum and your timing set where you want it, have at it. What you're looking to do is turn the idle screws in or out an egual number of turns, reset the idle back to your baseline setting, and take a look at the vacuum gauge. You're looking for the highest reading at your baseline idle speed. I usually only move the idle screws 1/8 of a turn at a time.

    When I used to have the stick, mine would pull 22.5" of vacuum at idle /forums/images/graemlins/eek.gif. Now with the 700r4 in gear and a lower idle speed, I do 19.5" Not bad for a 210/218 .447"/.462" cam /forums/images/graemlins/smirk.gif
     
  4. big pappa b

    big pappa b 3/4 ton status

    Joined:
    Jan 3, 2003
    Posts:
    6,328
    Likes Received:
    0
    Location:
    Falcon, Colorado
    I've ran much bigger hydraulic cams and didn't have a problem. If the above remedy doesnt work for you there is always the option of using a vacuum cannister. Lots of racers (street) use them when they run big cams. You can purchase them through Jegs or Summit
     
  5. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Deja vu! Didn't you start this exact same thread somewhere last night also? /forums/images/graemlins/shocked.gif
     
  6. 01fatboy

    01fatboy Registered Member

    Joined:
    Apr 25, 2003
    Posts:
    22
    Likes Received:
    0
    Location:
    Virginia
    i bought the engine rebuilt needed it in a hurry dont have cam specs have a unlite distributer and timing is set a 10 deg and connected to ported vacuum I adjust the mixture screws like you stated and it doesnt inprove it pretty much stays at 12 to 10 untill it goes south and just gets worse. all smog controls are removed so its not leaking somewhere. ordered a canister for now, may replace the cam well see if all other ideas will be helpfull thanks /forums/images/graemlins/ears.gif
     

Share This Page