Rebuilt top end of engine now carb idles much higher?Please help

Fuel and Air Systems

  1. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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    It's exactly the same just one crank revolution later.
    Your firing order is 18436572
    That is to say;
    1843 on the first revolution, and
    6572 on the second.
    As you can see, 1 and 6 are both at TDC at the same time; one is on compression, while the other is on split overlap, the period when both valves are slightly open.
    And the same goes for 8/5, 4/7, and 3/2.

    If you had a slanty, the firing order is 153624.
    153 over
    624, there are your paired cylinders again.

    A four cylinder with 1342;
    13 over
    42; same deal

    It's always the same on 4-strokes; first half of the firing order over second half, reveals the paired cylinders.

    Hope that was helpful
     
    Last edited: Sep 23, 2020
  2. CRUZE 418

    CRUZE 418 FABO Gold Member FABO Gold Member

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    Yes it was. The books usually illustrate it the way that I looked at it. It just seemed odd to me that after all of these years, a new generation has to do it differently. Ever go to a school math class lately? It is so totally different than when I went to school 60 years ago. No wonder the USA is so ______ up.
    Thank you for answering me AJ!
     
  3. LovetheA's

    LovetheA's FABO Gold Member FABO Gold Member

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    Everyone I was looking through my old photos when I installed the new chain and gears. Thankfully I take pics of everything. I found some old photos of the installation. I lined the gears up dot to dot just to get it dead accurate then rotated the crank to #1 cylinder TDC before dropping in distributor. Does this look dead on? I do realize that this doesn’t mean that the dampener couldn’t be off. My vacuum gauge and piston stop came in today so I’ll get to it this weekend? I understand without degreeing it it still could be off.

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  4. LovetheA's

    LovetheA's FABO Gold Member FABO Gold Member

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    Well I got my piston stop and proceeded to check TDC for cylinder #1. Let’s just say it was way off. No wonder I couldn’t get it to run right and idle nice after putting it back together. I included a photo so everyone can see how off the zero degrees was on the dampener. The actual factory dampener zero marking is all the way to the right. I dont really know what I did but appears to be 90deg off. I just want to make sure that I figured out the correct TDC. I put the damper on what I thought was zero then put the piston stop in. Cranked the dampener around until the piston hit the stop. Marked it. Then turned the dampener the other way and when it hit again stopped it and market it. The true TDC I figure is the middle of this marks. Now when I set the initial timing it should be around 10-15 BTDC. I have an electronic distributor with no vacuum advance and an MSD 6a. Not exactly sure how to set timing advance all in at 2500rpm with my electronic distributor? Any suggestions much appreciated. Thank so much everyone for the advise and help. 1A5DC48D-F351-4854-AF6E-0CD9FCAA7438.jpeg
     
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    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Well I have another question for everyone. I though I took care of the vacuum leak but I may still have one? First I took some starter fluid and while engine wasn’t real hot but warm sprayed it in between where the intake meets the heads. On the drivers side the starter fluid sat there and slowly evaporated. On the passengers side it was sucked in rather quickly and the engine idling changed. Therefore I though ah ha there is the vacuum leak. So I proceeded to rip the intake and carb off the engine for the third time and clean up all surfaces spotless and scraped off all the old permatex. After everything was clean I sprayed both sides of the valley pan. Where it meets the heads and where the intake meets the valley pan. I sprayed the areas liberally with copper gasket spray and laid down some little dabs of permatex oil and gas resistant sealer at the front back and along the front and rear rails where the valley pan sits. I put everything back together and let it sit for 24hrs. Then I rechecked the torquing of the bolts and started her up tonight. Well I think I still have a small vacuum leak. It doesn’t idle as rough but with the carburetor idle screw all the way down it still won’t idle below 1400rpm. It used to idle at 900-1000rpm. I tried spraying starter fluid again as before and it doesn’t seem to suck in but might be very slowly being drawn in on the passenger side not sure. When I cup my hands and cover the carb the engine idle slows down but I thought if covered tight enough it would stall out because lack of air flow into the engine. This didn’t happen. I thought if there is no vacuum leak sealing off the air into the carb would allow you to stall out the engine unless it was still getting some air in somewhere else? So is it possible that it could still be drawing air into the front and rear of the valley pan where it meets the top of the block and also the intake is still slightly leaking? I was going to buy a new valley pan and install and should I try to use a set of thin intake gaskets between the intake and valley pan on top but not between the valley pan and head? I don’t think 2 gaskets will allow the bolts holes to line up and for it to sit tight enough to the front and rear of the top of the engine rails. I’m at a loss and will be taking the intake and carb off for the 4th time. I’m at a loss. Getting frustrated but I’m not giving up. I recently bought a vacuum gauge. Can someone please tell me where would I attach the gauge to read vacuum on my 650 speed demon carb? Or do I go off the manifold? If I went off the carburetor I figured it would add in the carb as a possible culprit of the vacuum leak. Maybe the gasket between carb and intake? Thank you in advance for any advice.
      Carl
       
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      If there is a suggestion to use a gasket? What type of gasket would everyone suggest and what brand type of valley pan? Thanks
       
    • DrCharles

      DrCharles Well-Known Member

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      Don't forget it may also slow down because the mixture becomes overrich (your hands are acting like a choke).
       
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Yes it’s a big block a 383. I tried reusing the old valley pan when I reassembled it again and again. I’ll order a new valley pan(what brand) and maybe I should use a special type of intake gasket possibly between the intake and valley pan? Should I also use the copper spray and spray all meeting surfaces with the copper spray and lay down some oil and gas resistant permatex?
       
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Dr Charles I didn’t think about that.
       
    • lemondana

      lemondana BlackDart

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      You need to get a Chrysler throttle bracket for that carb.
       
    • jimjimjimmy

      jimjimjimmy lobsterman FABO Gold Member

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      if you have a leak on the ends of your valley pan this will not cause a vacuum leak , maybe an oil leak but not vacuum . also it looks like your bottom timing gear has more than one keyway if so which one did you use ? or maybe it's a shadow .
       
      Last edited: Oct 2, 2020
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Jimjimjimmy thank you for the heads up about the ends of the valley pan. I wasn’t aware of that. Why doesn’t it matter about the ends of the valley pan? I tried to use the keyway that allowed the bottom gear to line up properly based on the dots. I didn’t remove the keyway when I installed the new lower gear.
      Lemondana what is a throttle bracket and how would it help me?
       
    • 512Stroker

      512Stroker We are all here because we are not all there.

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      Carl is there anyone in your area (maybe a Forum member) that can walk you thru the fine art of tuning an engine? This is alot to learn w/o some first hand instruction.
       
      Last edited: Oct 2, 2020
    • 512Stroker

      512Stroker We are all here because we are not all there.

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      I never reused the valley pan always put on a new one nor did I use any sealer on the head or intake surfaces, just on the ends of the valley pan between the pan and the china walls to prevent oil seeping out - never had any vacuum or oil leaks.
      When you have it all apart and the surfaces thoroughly cleaned take a straight edge and a feeler gauge and check the head and intake surfaces for flatness.
      Were your cylinder heads milled by any chance?
       
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Cruze418
      I really appreciate you making the suggestion at some point that I may need to call in some help. I’m going to give it a last bit of honest effort before I do that. There are some things that are beyond my scope but this website has been such a valuable resource. I really can’t thank everyone enough for all their help.
       
    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      Make sure the secondaries are fully closed. Then,retard the timing, it WILL slow down.

      If your new damper-mark is off by 90* that could just mean that
      A) you used the wrong cylinder as #1, or
      B) the balancer is intended for a different timing cover.
      The #1 cylinder is the one closest to the rad, usually the drivers side .
      The last one to fire before #1 is #2....... they are 90* apart.... #2 is the passenger side front.
       
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