455 idle issues

Discussion in 'Street/strip 400/430/455' started by stubnosebrock, Jul 4, 2019.

  1. stubnosebrock

    stubnosebrock Well-Known Member

    Hello all. I'm running out of ideas on this, and its pretty frustrating. I have a 455 in my 71 skylark. Car has an HEI, and brand new 850cfm Proform carb. Initial timing is 14 degrees, vacuum advance is hooked up. Float levels are set, idle air screws are set as good as I can with a vacuum gauge. Engine pulls 14 inches of vacuum. There is no booster fuel drip. Electric choke is opening all the way. The problem is, the car kinda idles like crap, and it seems very inconsistent. Ill work on it, and get it to where it seems pretty happy, then the next time it runs, it seems different again. 180 degree thermostat, and 190-200 degree operating temp. Throttle response is crisp. It honestly seems like maybe its loading up at idle, but I dont understand how. I cant lean the idle screws out anymore with the idle getting even worse. Any ideas I havent thought of?
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    What cam?
     
  3. stubnosebrock

    stubnosebrock Well-Known Member

    I wish I knew. I bought the car with this engine in it. I was told it had a small cam, but you know how that goes. It doesnt seem like something at all big to me.
     
    Kingfish likes this.
  4. Gary Bohannon

    Gary Bohannon Well-Known Member

    What intake manifold do you have?
    Some Edelbrocks have carb mount holes drilled all the way through. My B4B has 8 holes for Holly and Qjet and 2 were just peeping through the metal and sucking air. Check all of them for the tiniest break through. Sneaky leak.
     
  5. stubnosebrock

    stubnosebrock Well-Known Member

    Gary, Its a Eddy performer. Very good idea, and ill check on that
     
  6. 1969RIVI

    1969RIVI Well-Known Member

    Check the the rubber lines and caps on your carb. I had the same kinda issue earlier in the season. I ended up finding tiny hairline splits in the lines from the vac canisters that caused a vacuum leak and one dried out cap on the front sucking in air. I replaced them and everything thing is good to go. Even if you think because your carb is new you shouldn't have problems check it anyways. I bought a fully restored Qjet a year ago and within that time frame the under hood engine heat baked the rubber lines and caps until they were brittle and split. I'll be checking mine every year from now on.
     
    matt68gs400 likes this.
  7. Gary Bohannon

    Gary Bohannon Well-Known Member

    Ceramic coat your exhaust manifolds or headers.
    The significant reduction in under hood temperatures will make you enjoy opening your hood. Your rubbers are less apt to break, and may last for years! Your hood paint may like it too.
    It improves power as well, because the intake, carb, fuel, and incoming air is much cooler. Also, the captured hot exhaust gasses are moving faster and scavenging is improved.
     
    1969RIVI likes this.
  8. hugger

    hugger Well-Known Member

    Four corner idle?
    14° initial means nothing ,..it may take 20 or more what's the total advance?
    Mechanical carb?
     
  9. Schurkey

    Schurkey Silver Level contributor

    What is the cranking compression of all eight? What is the cylinder leakage of all eight? Ever tried a cylinder-balance test?

    Moderate chance you aren't getting enough fuel at idle.

    180 thermostat but 190--200 operating temperature at idle or cruise, = cooling problems in most cases.
     
  10. Stevem

    Stevem Well-Known Member

    With the motor idling at normal running temp does closing the choke down by hand make for a rpm increase?
    Even if it's got a hotter cam then stock 14 inches at idle does not sound right for 455 cubes , it would make me wonder if the Cam was in right, or if the timing chain is going south!
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Lots of cams like higher initial advance. I locked mine out at 34* and use the 20* start retard in the MSD digital 6 box. It idles consistently like that with 15” at 900 in Park, and 12” in gear at 750.
     
  12. Quick Buick

    Quick Buick Arlington Wa

    This Is just food for thought... Im guessing you have a mystery Motor. I know I did... Maybe the cam installer used a cheap internet set up.. the lifters we get today are literally garbage. Summit, Jegs, EPW etc does not carry any usable lifters for a buick .....
    Yes there are great ones out there as long as you know which ones....Camshafts they are on the same boat...

    Oil ......... Not many people really know about the the changes in the oils we get today.. They understand its better than yesterdays oil.. But thats for todays motor.. Not yesterdays Motors..

    Well my my Mystery motor is in a scrap pile..
     
  13. mrolds69

    mrolds69 "The Cure"

    Hey Brandon, I thought you went to the dark side? I went up to NY before for some AC stuff you had. Welcome back!
     
    stubnosebrock likes this.
  14. stubnosebrock

    stubnosebrock Well-Known Member

    Frank my old friend! Good to hear from you! I hope things are well on your end. Yes, after I sold my yellow 70 Buick, I had a 70 Duster for a while. Ive since sold that, and I have been restoring a 68 Roadrunner for a few years now. I just recently bought a 71 Skylark to have something to cruise with until the Roadrunner gets done. I dont know if its a long term car for me, but maybe? Now if I just buy an AMC, I can have all the most expensive stuff to build haha.
     
    mrolds69 likes this.
  15. stubnosebrock

    stubnosebrock Well-Known Member

    Thanks for the input everyone, I messed with car tuning again, and was able to back the left secondary idle air screw out a bit more, which helped the idle a lot. It seems pretty happy now. Now I have a running too hot issue, as stated above. The hotter it gets, the less happy the car is. Im not surprised as the radiator is likely the stock 2 barrel 350 rad. So I just ordered a 4 row aluminum from Champion. That oughta keep it cool! Ill keep this updated when it comes, and see if it helps my issues.
     
  16. telriv

    telriv Founders Club Member

    WRONG RAD!!!! 2 row with at least 1" tubes. Better if 1 1/4" tubes. More surface cooling area.
     
    1973gs likes this.
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I hope you meant 2 row. A 4 row aluminum is likely inferior to a 4 row brass copper radiator.
     
  18. stubnosebrock

    stubnosebrock Well-Known Member

  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I hope it works for you, but you should have done some reading here first. I have posted about this countless times. The whole point of using aluminum, other than weight reduction, is that it is stiffer and can support tube sizes up to 1 1/2”. More tube to fin contact, more cooling capacity. Brass/Copper is soft so tube size is limited to 5/8” or so to prevent ballooning of the tubes. Brass/Copper conducts heat better than aluminum but tube size makes the difference. The best aluminum radiators are 1 or 2 row because that’s all you need. That 4 row has small tubes and likely cools worse than an equivalent brass copper.
     
    Last edited: Jul 9, 2019
    Dadrider likes this.
  20. matt68gs400

    matt68gs400 Well-Known Member

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