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  1. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    So I have some news! I ran the truck a bit more and checked one last time for vacuum leaks with carb clean. This time I found one at the secondary barrels shaft. If I spray cleaner at the choke side of the secondaries it almost immediately revs up and runs better! The other side makes a slight...
  2. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    Well I'v got updates. The replaced vacuum advance definitely helped the issue! It now will idle with choke off! But it still does not idle smoothly at all. It shakes and misses and just generally runs badly. I have tried everything. I have moved the timing every which way and that did not...
  3. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    That makes a ton of sense! Thanks for explaining that. That may just be my issue. I will be able to work on it Saturday and Ill let you know how it goes. Thanks again for both of your help!
  4. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    What you said about the timing makes sense and I appreciate your explanation. My vacuum is about 15-16 at idle. It is extremely steady and does not move at all. Vacuum hardly moves while turning idle screws. the only time it increases is when engine speed changes. Unfortunately I will not be...
  5. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    Yes. The timing will advance without the advance being hooked up. I am assuming that means the centrifugal advance is working like it should be. I do not know how far it is increasing because my timing light has no adjustment. I can only see timing by the marks by the harmonic tab. What should...
  6. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    Here's what I did for a vacuum check. I sprayed carb cleaner around the base of the carb and carb shafts. No change in RPM. What's funny is there is not much change even if I spray it right into the intake. I have not checked by disconnecting and blocking off all vacuum lines I will be doing...
  7. J

    Idle Mixture Screws Do Not Adjust Anything on 1974 454.

    Hello Everyone first post here! I bought a rough, but not rotten 1984 C20 Squarebody! I bought it thinking that it was a 350 small block, but it turned out to be a 305 ): I wanted a bit more get up and go than what it had so I bought a 1974 454 Big Block for it. Once installed in the truck I...

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