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  1. jjrowe

    Stumbling and backfiring carb question

    The truck is running well now. I found that the VSV connections were not correct. Here is how everything is connected now. White goes to distributor. Red goes to carb base (manifold vacuum) Black goes to manifold connection under air cleaner Green goes to throttle position diaphragm The...
  2. jjrowe

    Stumbling and backfiring carb question

    For a vacuum retarding distributor, how can the VSV apply vacuum at WOT? The source vacuum from the manifold has dropped. I guess it works because according to the Haynes manual, during acceleration between 13-41 mph, the VSV is energized to retard timing. I assume then that I shouldn’t have...
  3. jjrowe

    Stumbling and backfiring carb question

    Now that is a new one, I would like to learn more. You are saying my timing should advance up to a point and then retard under high output? And this would be accomplished in my 1972 distributor how? Here is another thread where someone mapped timing advance against rpm. No where do you see a...
  4. jjrowe

    Stumbling and backfiring carb question

    Yeah. I checked it with the timing light with vacuum applied.
  5. jjrowe

    Stumbling and backfiring carb question

    The main issue seems to be my VSV isn't working properly. To bypass that for now, I connected my distributor vacuum directly to the base of the carburetor (manifold vacuum) and reset the timing. A retarding distributor cannot be timed to the bulb without manifold vacuum or it will be too...
  6. jjrowe

    Stumbling and backfiring carb question

    In the video I am parked in neutral and there is some hesitation. I’ll try it again and see if I can get the idle down. I brought the timing back down, and with the VSV disconnected, I am not seeing the carb backfire like I was. That vacuum loss through the VSV appears to be at least part of my...
  7. jjrowe

    Stumbling and backfiring carb question

    I believe I have a retarding distributor and its vacuum is hooked to the VSV. I’m not measuring any vacuum at that port. Edit: I connected the distributor directly to the port at the bottom of the carb and it started to run rough. So vacuum does seem to retarding the timing.
  8. jjrowe

    Stumbling and backfiring carb question

    Looks like what I need. Let me know your price and how to pay you.
  9. jjrowe

    Stumbling and backfiring carb question

    Carburetor video while running. https://youtube.com/shorts/xwICzBuZBoA
  10. jjrowe

    Stumbling and backfiring carb question

    Did some more testing. 1. Disconnecting fuel solenoid wire causes the engine to die immediately. 2. Vacuum I measured before was teed into the manifold port that went to the VSV. If I measure directly from manifold I get a good 21 in. So I’m losing vacuum inside the VSV. Not sure if that is a...
  11. jjrowe

    Stumbling and backfiring carb question

    At 7 BTDC it will idle ok, but backfire/sputter as soon as it is revved. Pretty much not driveable. At 20 BTDC it seems to run fine with no backfire or sputter. The only issue is the idle is high and it may not be good to run long term with that much advance.
  12. jjrowe

    Stumbling and backfiring carb question

    I have pretty solid vacuum numbers so I don’t think there is a intake leak. Would the sight glass have fuel if there was a fuel starvation problem? I can manually rev it and watch the glass, it will backfire but the glass still shows fuel. The idle speed screw is currently not doing anything...
  13. jjrowe

    Stumbling and backfiring carb question

    Filter in that fitting on top of the intake to keep backfires from damaging the VSV I think.
  14. jjrowe

    Stumbling and backfiring carb question

    I also took some vacuum measurements. vacuum at the brake booster is 21in vacuum from VSV to the bottom of the carb is 14in vacuum from the manifold to VSV is 14in vacuum to distributor from VSV is 0 - revving has no effect vacuum to top of carburetor (actuator) from VSV is 0 - (only opens at...
  15. jjrowe

    Stumbling and backfiring carb question

    Got it, thank you!
  16. jjrowe

    Stumbling and backfiring carb question

    Couldn't agree more! The idle is ok at 7 BTDC but it stumbles and backfires as soon as you take off. Fuel pump looks relatively new, I am going to replace the fuel filter next. I'll check the advance and see if the timing changes at higher RPMs.
  17. jjrowe

    Stumbling and backfiring carb question

    I did attempt to use the Fel pro gasket but I didn’t like the fit. The gasket they are selling is like a combo gasket for both F and 2F. Notice the bolt holes on each end...
  18. jjrowe

    Stumbling and backfiring carb question

    If you have that weight please let me know and I will pay pal or Venmo the cost. Thank you!
  19. jjrowe

    Stumbling and backfiring carb question

    Pin_Head, did you see my first post about the missing weight? Have you seen that before. I suspect someone lost the weight and just threw a ball in there. I wonder how that is affecting function.
  20. jjrowe

    Stumbling and backfiring carb question

    Thank you all. I checked with the brake booster line plugged, didn't seem to help. I put a new hose on the booster anyway because the old one was cracking. I did notice an RPM increase when I sprayed WD-40 directly where the intake manifold meets the head. The manifold nuts and bolts are...
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