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I need help!

Discussion in '40- & 55-Series Tech' started by offcamber40, Nov 13, 2003.

  1. offcamber40

    offcamber40

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    Allright, after a month of slowly rebuilding the motor on my 76 40, I got it all back together, and am having some running issues. I am running a new weber 38/38 (w/ a pressure reg) with a new non-usa dist w/ a petronix igniter replacing the points and a high output coil.. internally everything was remachined, new timing gears, rv grind cam, and a rebuilt head.. basically everything is new or refurbrished. The car starts and runs at idle, but it is rough. If left to sit idling the engine will run fine for a while, then sputter and pop, then come back up to normal idle, then slowly die.. Increasing the idle speed smooths out the motor.. I get good advance and smooth running if I slowly bring the engine up to speed, but hard depression of the gas causes it to miss then backfire out the carb. Ive dialed in the timing the best I can by ear (anyone know the specs for the non-usa dist?) Could this be a vacuum leak? I was thinking maybe I am getting a leak where I had to pull the factory studs to mount the carb adapter plate? It is driving me nuts!

    Mike
     
  2. toddslater

    toddslater

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    Might you be 180 out ?
     
  3. dd113

    dd113

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    Todd S called it. I bet you are 180' out. GO by stock values to set initial timing then advance it until you png or drop off. Put a Vac gauge on it and see where you are. Vac should be around 20ish if newer motor but main thing is steady vac. Jumping vac or flucuating vac indicates issues.
     
  4. Pin_Head

    Pin_Head

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    If it was 180 degrees off, it wouldn't run; just backfire and pop a lot trying to start it.

    It sounds like carb issues. All you folks with 38/38s step up. If it was me, I would put a Aisin on it.
     
  5. Bobsbash

    Bobsbash

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    I also agree that if it was 180 degrees off it wouldn't even run. It would just pop.

    I had a similar problem with my cruiser. If the carburetor is new and working properly I would then check my fuel lines. If they are old you might want to replace them. Look for weak lines that could colapse when put under working conditions. Make sure your fuel filter is in between the pump and carb and that there are no kinks in the line. You want to make sure there are no 90 degree bends. Straight or 45 degree is the way to go. 90 degree bends add alot of friction to the flow.

    You mention that a hard depresion of the gas results in backfire and sputtering. A vacuum leak is possible along with decreased fuel flow. I would consider putting a vacuum gauge on along with a fuel pressure gauge. Both will help you diagnose problems and help the the tuning of your carburetor. It is not too expensive of a mod. I would advice getting some books on tuning your carb. I know it helped me understand how my engine ran and how to diagnose carb problems.
     
  6. 73lndcrsr

    73lndcrsr SILVER Star

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    I would bet timing is your issue. I had help getting mine done. Here is what I did.

    crank the engine, let it idle smoothly.
    slowly rotate the dist. counterclockwise. I only turned it a couple of degrees at a time.
    rev the engine to see if the sputtering starts to go away.
    stop the engine and re-start ( to make sure it will still crank easily)

    Repeat the process until you get smooth reving from idle.

    take a drive, get into 4th gear at about 35 MPH. accelerate and listen for pinging
    If it pings back the timing off a little and retest.
    If it does not advance it a little more and retest.

    Hope this helps.
     
  7. Gumby

    Gumby Supamod Staff Member s-Moderator

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    I'm voting for your valves are too tight. That or a vacuum leak. Spray some carb clean at your intake manifold sealing surfaces and the carb base plate. A change will indicate a leak.
     
  8. toddslater

    toddslater

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    Now granted I've never been 180 out with either of my cruisers...but over the years I managed to be ass backwards a time or two. Most recently about 3 weeks ago when I re-assembled my fathers 63 mercedes 190 (inline 4 banger). Got everything all squared away etc...etc..etc..was difficult to fire up but it did and acted exactly as Mike's motor. Scratched my head for awhile, twisted the dist this way then that..paged thru the manual...brought everybody back up to TDC...then a latent brain cell evoked a memory of many moons ago when I rebuilt my TVR motor (inline 6). I looked at the merc cap and then proceeded to do the 180 shuffle of the plug wires (too lazy to pull the dist and give it a 180 spin). Problemo solved. As I mentioned I have never been down this road with either cruiser...but it takes all of two seconds to rule this out.

    Should this not be the case and you've checked for vac leaks, make sure you have your pressure reg dialed in at 2.5 to 3 psi.
     
  9. Rice

    Rice SILVER Star

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    If you're using a stock fuel pump I'd suggest getting rid of the pressure regulator.
     
  10. offcamber40

    offcamber40

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    Thanks for the replys everyone.. the engine is not 180 out, it was at first when I installed the dist., I set it to TDC on what I thought was one, but turned out to be six. I first noticed the problem when I cold adjusted my valves, and a couple were waaay out! I reinstalled the distributor properly before initial fire-up. I re-used my brass air rail block-offs from my old head, do these need to be replaced? Were they originally tapered, where they may not be anymore? I am going to re-adjust the valves tonight Gumby, your suggestion may be the problem, as I totally forgot to re-adjust them after initial warm-up (I got excited that it ran under its own power after a personal rebuild, you guys know that feeling!) There is also a block-off that came with the weber for an optional power brake vac advance on the adapter plate which may be causing problems.. will teflon pipe sealer tape work in fuel/heat areas to solve vac problems on threaded parts?
     
  11. offcamber40

    offcamber40

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    OK, sorry to stack a couple of posts, but I adjusted the valvetrain hot, and still have the same running issues.. I pulled the vacuum line off the distributor to test for vac, and no problems. With the vac line disconnected I blipped the throttle and got the same hesitation/miss problem as when it was connected, run the engine up to speed, and it is the same as connected.. Im confused? what would cause the distributor to not be advancing properly when it is recieving good vacuum?

    Mike
     
  12. cruiserka

    cruiserka

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    maybe its not your distributor? maybe you accelerator pump in shooting too much or too little gas? how bout float level?
     
  13. 73lndcrsr

    73lndcrsr SILVER Star

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    Where are you pulling your vacume from? It should be ported vacume from the carb. If you are running off of the manifold or somewhere the vacume is constant you will have too much advance at idle.
     
  14. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    Get it running, and do as Gumby instructed, spray carb cleaner at the base of the carb, and and I would check the manifold where it meets the head. Did you retourque the manifold fasteners when it was hot? You could have a leak there too. I will bet that you find a vac. leak. If it starts right up and "runs" you do not have a spark issue. As per your description, It sounds to me like you have a fuel/air metering issue.

    Good luck!

    -Steve
     
  15. offcamber40

    offcamber40

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    I will be checking for vacuum leaks today, I picked up a can of carb cleaner last night. The distributor is hooked up to the correct vacuum port on the new carb.. another thought, the car sat for about 2 months, I replaced the fuel filter, but could my gas be the issue? Should I drain the tank and get fresh? I may just run a piece of fuel line to a container of fresh gas to see if it changes anything.. I hate draining tanks, gas all over! I will let you guys know whats going on later tonight.

    Mike
     
  16. offcamber40

    offcamber40

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    I checked for all vacuum leaks and could not locate any. My MAF header has a leak at the gaskets (I doubled 2 up to try to seal the problem). Will this leak cause a running issue? I also checked the vac advance on the distributor with a vac pump/gauge, and it is working fine. I had been running a hotter plug, so I went to the store and picked up a correct set of NGK's and gapped them. Should I gap them in spec to Non-USA 40s b/c of my non-usa distributor and no wmissions control? Ive got it running a little better, but it still hesitates at full throttle, or under heavy load.. Im going to keep fiddling.
     
  17. IDave

    IDave

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    Definitely a manifold/header gasket leak will affect your vacuum.
     
  18. offcamber40

    offcamber40

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    Idave, I meant to say that there is an exaust leak where the header has warped and doesnt hit the gasket properly.. As far as I can tell there is no vacuum leak at the manifold, just exhaust. Would an exaust leak at the head cause a running problem? I have not had this problem before on other cars so I am in unfamiliar territory.

    Thanks
     
  19. IDave

    IDave

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    I might be beyond my experience answering, too, but I think you are right: it won't cause any problems with running if it is an exhaust leak. Would not be healthy for the driver and passengers, though!