It's gotta be a vacuum leak ... right?

Discussion in 'Workshop Forum' started by Huey, Jun 24, 2019.

  1. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    I just played with the ignition timing with the vacuum still connected. I'll have to fiddle with it some more and probably make minor tweaks to the cam timing. I wish I could find a shop that I could just pay to do this for me but everyone I called said it's too old and/or too mysterious and they don't want to mess with it. I would gladly take it up to Columbus to MWB but they can't get me in until sometime in August and I would really like to drive this stupid thing.
     
  2. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    Update. Today I replaced the aux air valve (man, lets hope I never have to that again.). I also bypassed tha a/c up idle valve since I read that is a common cause of air leakage. Neither of those things made a difference.

    I played around with the ignition timing to where it runs out real good but still idles fast. Twiddled with the idle adjustments and got it to where it still idles fast but not obnoxious.

    I then made a tiny tweak to the cam pulley but it seemed to make no difference.

    Bottom line is it runs ok. At 60-70 mph it feels good. Takes off in 1st gear good. Idles fast and still has the pop pop pop miss.

    But something new. When I shut it off after driving it a while it doesn’t want to crank over — this could be overheated starter or a symptom of advanced timing. It also misses like crazy and sounds like an old Volkswagen until I start driving it. This only happens after driving and at full temp.
     
  3. Jefco

    Jefco Daily Driver

    Location:
    Portland OR
    Is it possible you got the timing 180 degrees out during the cam gear switch?
     
  4. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Hi Huey,

    I pulled the top cam gear cover section off of my 85's engine today to confirm the setup. I have a 1500/FI with the MWB performance head. There is a long story on the history of this car, but the short story is this: Matt brought the car to MWB to complete the performance head install for the PO. The engine is set up with a stock stamped cam gear. No fancy adjustable gear involved. I have owned the car since 2013 and it has always run well for me.
    20190714_130351.jpg

    When I started my never completed 78 1500/FI swap, I bought a MWB performance head for the project. Matt told me that an adjustable cam gear can help you squeeze more performance from the engine, but that it wasn't necessary to make it run well.

    I know I am not solving your problem, just providing you with an option to try if you can't work out the current timing issue with the adjustable gear.
     
  5. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    Thanks, that helps. I understood from him that an adjustment was required but maybe I wasn’t understanding him correctly. I adjusted it as best I could per the instructions but was afraid I got it wrong. I’ll keep fiddling with it. It runs and drives so at least I can enjoy it for a while.
     
  6. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    My understanding was that the timing marks would not align after the initial hand turning of the engine. It will be off around 1/2 tooth (~4 degrees). So it can be set up retarded or advanced 1/2 tooth. Setting it to be 1/2 tooth advanced the recommended way to go. I went over to the MWB site and read through the description for the 10 bolt FI performance head I purchased and found this paragraph:
    So the engine will run with the stock pulley, the adjustable pulley will let you fine tune. I wish I could be more help.
     
  7. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    The instructions I received with the cam said that cyl 1 should be set so the intake valve is open 0.050” at 3.2 degrees BTDC. They told me that setting it at 0.050” at exactly TDC would be close enough so that is what attempted to do.

    I set the cam gear and crankshaft at TDC and then used a dial indicator to roll the cam back until the indicator was at 0.050. But getting a dial indicator on the valve tappet is damn near impossible on this engine. Plus my dial indicator was made in China so it could be off.

    Either way I think it is as close as can possibly be. I think the ignition timing is still off or perhaps my distributor is not advancing properly. Or I have an air leak but I sure can’t locate one.

    It runs great except at idle and when the engine gets to full temp then it gets finicky.
     
  8. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Maybe I am way off base in responding. Did you just put in a cam? Or did you install a performance head with a new cam? If you just put in a cam my advice is basically worthless.
     
  9. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    I had MWB redo the head. They sent me a completed head with the cam tower and camshaft already installed. But since the cam tower was shaved, it changed the clearances requiring the need for the adjustable pulley (per my understanding.)
     
  10. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Got it, so full set of MWB parts. I bought mine back in 2010, so I guess the directions have changed. Or what we ordered was just different specs. I have never started the engine, so I really don't know. Laziness and real life issues have given me too many excuses in putting it off. :(
     
  11. lookforjoe

    lookforjoe True Classic

    Did you also use the 1300 tensioner?
     
  12. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    Yes. But I'm hoping they sent me the right one because I saw no visual differences between my original tensioner bracket and the 1300 one.
     
  13. lookforjoe

    lookforjoe True Classic

    The tensioner is a different OD, I reused my 1500 bracket, don't think the bracket matters, besides being easier to not worry about pressing the bearing yourself.
     
  14. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    Hi Hussein,

    According to MWB description I quoted above, the bracket does matter. MWB recommends a 1500 t-belt, 1300 bearing and 1300 bearing bracket. Let's see if I can borrow an image from Don's post over in the FS&W where he is asking for a 1300 bearing:
    ----------------
    Here is a picture of the 1300 beside the 1500. The 1300 has a lower shoulder.
    [​IMG]
     
  15. lookforjoe

    lookforjoe True Classic

    Thanks Jim - that's interesting - I don't recall having an issue seating the 1300 bearing. I don't use that setup with my 1600 build. Obviously safer to err on the side of caution and use the paired bearing/carrier.
     
  16. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    I dug up a couple side by side pictures of the 1300 vs 1500 brackets. I took these while I was assembling my engine, so naturally I don't have both in hand anymore for better pics or comparisons. I was sure I had taken pictures with the caliper measuring each bracket's barrel, but I can't find them.

    Without the measurement pics, I am not sure there is much to learn from these. The barrel on the 1300 bracket is a little larger as well as the bearing. Which is why those parts are used to take up the little bit of extra slack in the belt caused by shaving the head.

    1300 on the left 1500 on the right
    13-15-tensioner_1.JPG

    1300 on the left 1500 on the right again and you can see the part #s
    13-15-tensioner_2.JPG

    1500 on the left 1300 on the right, so much for consistency in placement :rolleyes:
    13-15-tensioner_3.JPG
     
    kmead likes this.
  17. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    Just ordered a smoke tester machine. I will find this problem, I’m on a mission.
     
  18. Dan Sarandrea (Phila)

    Dan Sarandrea (Phila) Waitin' On Parts...

    Location:
    Philadelphia, PA
    I have a buddy who has been a mechanic for over 45 years, he absolutely RAVES about the virtues of a good smoke machine :)
     
  19. kmead

    kmead Old enough to know better

    Location:
    Michigan
    I thought a smoke machine only worked on Lucas electrical systems to reinject the lost smoke properly.

    Or is this something different?
     
    Huey and Dan Sarandrea (Phila) like this.
  20. Huey

    Huey True Classic

    Location:
    Xenia, Ohio
    Drove it today and it runs great. It still has an uneven idle and doesn’t like to start again when it’s hot (it does start but it runs rough until I get moving). But it runs great, holds its temp, and cruises beautifully in 5th gear. I don’t know what I did.

    I also scored a new NOS A/C compressor so maybe I can get that working again.

    Now I need to focus on making it look 100%.
     
    lookforjoe, kmead and JimD like this.

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