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Engine startup help

Discussion in 'The Hokey Ass Message Board' started by ErikDaViking, Mar 18, 2012.

  1. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Hey there. I've recently brought a Chevy 250 inline 6 back to life after a rebuild, having some minor issues I thought you guys might be able to help with.

    It a fresh rebuild, everything new or machined back to specifications. I added dual carbs and an Offenhauser manifold, along with cast iron headers. The manifold is NOT heated. Has a Pertronix Ignitor 1 in it.

    She starts up pretty easy, although I don't have the timing dialed in completely yet. Once started, it idles nice and strong, real smooth. However, after about a minute, maybe two, it starts popping through the carbs and dies. My first thought was that it wasn't getting fuel. I have a clear glass filter, and I can see fuel in it, although not as much as I would have thought. Still, it will idle a long time before dying, longer than when its just the bowls full of gas. It is never more than 1/2 full though, and usually looks lower than that. I did bring her up to a fairly good RPM last time and ran for a while, it didn't die or sputter at higher RPMs, but wouldn't idle at all and was sputtering through the carbs when I brought her down.

    There is also a lot of vapor coming out of the breather cap, but its an old style with a steel cap filled with steel wool and thats about it. I never saw this engine run before I rebuilt it, not sure if this is normal.

    I am trying to figure out if its a fuel issue or if its something in the timing or carbs. I am leaning towards fuel, probably gonna try a new fuel pump, but this one was new when it was put on. I just feel like I should see more pressure into the filter. Another thing I thought of was that it is in the carbs somewhere, some adjustment or something. Unfortunately I don't know much about carbeuerators, and even less about dual set ups. I don't think its timing because it runs great then suddenly goes to shit. Seems like timing would be consistently bad.

    Any thoughts or ideas?
     
  2. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    I'd simplify and block 1 carb off - like a plate under it to seal it off. Is it a mechanical or hydraulic cam? Did you adjust the valve train after rebuild or was it adjusted at the machine shop?
     
  3. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Its got hydraulic lifters, solid not roller though. I adjusted the valves when we put the head on.
     
  4. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    This is what my fuel filter looks like, how much fuel should I be seeing coming through it?

    [​IMG]
     

  5. Boryca
    Joined: Jul 18, 2011
    Posts: 709

    Boryca
    Member
    from Detroit

    In that orientation you'll only ever have a half full filter. I don't like those fuel filters though. They look pretty, but don't filter much. You're better off with the steel can type.
     
  6. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    They always have a lot of air. You can flow test the pump by disconnecting after the filter, to see how fast the pump can "half fill" a soda bottle. You don't need lots of pressure for the problem you have. Even gravity feed would be enough to idle and drive.

    You need to make a bracket to hold all the weight of that brass T and filter, when using copper tubing. It may work harden and crack at one of the fittings.
     
  7. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    OK, I just went out and started it again, nothing different. Now its idling perfectly, been running about 10 minutes with no issues. Guess its not the fuel, the filter looks the same. I really am stumped here. I'm letting it idle for its breakin now, guess I just need to dial in the timing and the carbs and see what happens. Any thoughts?

    Also, thats a good idea on the bracket. I can see the line vibrate when it runs.

    Thanks for the input so far.
     
  8. I assume you meant "hydraulic, FLAT TAPPET not roller". It can be a little messy but I'd suggest re-adjusting the lifters with the engine running. Is the distributor new, or just the Pertronix unit? Maybe check the distributor for shaft and/or bushing wear. With points this can mess with the dwell at idle speeds but might not be that much of an issue with the electronic conversion. Is the vacuum and mechanical advance working properly.
     
  9. afaulk
    Joined: Jul 20, 2011
    Posts: 1,194

    afaulk
    Member

    Uh....you're not supposed to break a flat tappet cam in at an idle. Start it and immediately bring RPMs up to about 2,500 for 20 min or so. If it gets too warm, shut it down and after cool down, complete the 20 min break in period.
     
  10. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Thanks Claymart, thats what I meant. Couldn't remember the right terminology. As a matter of fact, the distributor in not new, and I think it needs replaced, I could kinda see some movement on it.

    afaulk, there's about a thousand ways to break in an engine, I saw the half hour at idle most often. I did run it up to about 2500 or so for 5minutes after the half hour. We'll see...I think it will be good, if nothing else these 250's are solid engines, like a tank.
     
  11. randydupree
    Joined: May 19, 2005
    Posts: 667

    randydupree
    Member
    from archer fl

    No.
    Nobody breaks in a new engine at idle.
    And,as soon as you start a new engine you need the timing light on it and set the timing pronto.
    I guess you never heard of detonation?
    Set the timing,run it up to 2500rpm for 30 minutes,no less.
    Look for leaks,keep it cool.
     
  12. Armstrong
    Joined: Apr 17, 2004
    Posts: 371

    Armstrong
    Member

    I had a similar problem with a set up alot like yours. It turned out to be too much fuel pressure causing carbs to slowly flood. A fuel pressure regulator fixed it.
     
  13. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Randy, thats just not true. You will find a lot of people that recommend between 20 minutes and half an hour at fast idle, then varied speed and load for the next 500 or so miles, avoiding long stretches at a constant RPM. People passionately believe in both methods, and both swear the other way will ruin your engine. The machine shop that did the block recommended this way, I picked it. Guess I'll find out one way or the other, but I'm pretty confident it'll turn out ok.

    Good point on the timing though, I wish I had done that. Too late now. Next time I start her up, I guess.

    Armstrong, thanks. I'll check that.
     
  14. MikeRose
    Joined: Oct 7, 2004
    Posts: 1,583

    MikeRose
    Member
    from Yuma, AZ

    Could be a fuel system venting issue. I had a cadillac that had a similar problem. It would idle and drive short distances, but then would act like it ran out of gas. Fuel filter always looked like yours, just a little fuel flowing through.

    Have you looked inside the carbs after it dies, to see if fuel is squirting in when you give it gas?

    Maybe try an electric pump?
     
  15. chettar
    Joined: Nov 15, 2008
    Posts: 120

    chettar
    Member

    Breaking in at idle speed will flatten the cam!!! It has to be run at about 2,500rpm for a minimum of 20 minutes. This is the biggest mistake everyone makes when breaking in a flat tappet cam. Did you put any ZDDP (Zinc additive) in the oil before you started the engine? If not call Patrick at Patrick Antiques and let him tell you how many cams he has replaced because people did not add Zinc to their oil. Don't worry about the fuel level in the filter that where it should be. I would do a compression check to make sure that you have not created a problem by your low rpm break in, if OK then i would check the valve settings which is 8 for intake, and 16 for exhaust.
     
  16. Curly5759
    Joined: Jan 23, 2012
    Posts: 66

    Curly5759
    Member
    from Aridzona

    Just throwing this out there-- Unheated manifold/Wash. State/Winter = Carbs freezing up?

    Curly
     
  17. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Chettar, I did use zinc additive, gotta make modern oil slippery! I'll do a compression check and see where we are with that. I don't understand how a low rpm break in would be any more damaging to a cam lobe than a high rpm one though. I can see the argument that the rings won't seat right, but what difference would it make to a cam, as long as oil pressure is good?
     
  18. ErikDaViking
    Joined: Aug 11, 2010
    Posts: 171

    ErikDaViking
    Member

    Curly, thats one thing I was wondering. I'm really hoping to avoid running hoses to the manifold, I want to keep it as clean under the hood as possible, but I have a plate for it just in case. I have heard people say their engine runs like crap without it, and also people in all climates that say they have an engine that runs fine without it. Figure I can always go back and add it if need be.
     

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