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Thread: Avenger 870

  1. #1

    Default Avenger 870

    I have an 870 and brand new install crate engine. 400 Pontiac stroked to 455, Crane cam, KRE heads. At idle engine produces roughly 6-8" vacuum. This carb has been a challenge to say the least from the get go. First, ran very rich at start, plugs were soaking wet...rejet from 82 down to 78, problem solved. Second problem, when driving car, it runs on as if on cruise control. Also, at normal start (acceleration) from stop the engine stumbles hesitates like it is not getting enough fuel. I changed both power valves - front was 4.5, rear was 3.5, changed them both to 2.5. That problem is just about gone...but the run on persists. I have to kick the throttle to get it off this run on sensation. The choke has been adjusted clockwise and counterclockwise, and yes it works as it should. Any thoughts on this would be great!

  2. #2
    Join Date
    Dec 2009


    Check this:
    Adjust the primary throttle blades (idle speed screw) to expose no more than .025"-.030" of the idle transfer slots.
    They're located under the primary throttle blades - must remove carburetor to measure with wire. Common problem.
    If so, you'll need to open the secondary blades a little bit, in order to close the primary blades (to maintain desired idle speed).
    When the idle transfer slots are exposed too much, it renders the idle mixture screws useless.
    (Watch video titled "How To Adjust The Secondary Speed Screw".)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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