Here's a puzzler
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Here's a puzzler

  1. #1
    Glendale Arizona Squirtcha?'s Avatar
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    Default Here's a puzzler

    At least it's puzzling the heck out of me. Motor is a 468 cu in BBF basically stock. Hydraulic flat tappet cam, roller rockers, Comp pushrods with guideplates, stock crank and rods, edelbrock Performer RPM heads with small chambers (75cc) and about 10.5:1 compression, tunnelram with two holley 750 dps.

    Problem new fuel pump carbs and 4 port regulator. Fuel pressure is at 6.5 psi, idle mixture screws are 1.5 turns out and floats adjusted.

    One pump on the throttle when cold and she lights right up. Idle sounds real good and no indication of any problem. When running there's a bit of a hesitation off idle then she gets up and runs pretty good (thinking this is unrelated to the problem but something else to work on).

    While under way sounds like it's hitting on all 8 cylinders and I'm pulling my normal rpm at WOT and various ranges of throttle. Ran it about 4 miles just taking it easy most the way and romping on it a few times. Got to the cove and let her settle into an idle and it sounds like it's running on 7. Kinda popping and coughing. Got into the cove and let it sit for a bit. After about 10 minutes I disconnected my driveline via the jetaway and it fired right up and sounded normal again.

    Later left the cove and did the same routine on the way back. Started up with a bump of the key and sounded fine at idle, cruise and everything in between, but when I got back to the ramp and let it idle it started crapping out again. After it's on the trailer for ten minutes or so, fire it back up and everything is back to normal again.

    I'm thinking I've got a hydraulic lifter taking a shit one me. Can't figure out what could be changing from cruise to idle and why after sitting everythings o.k. again. Keep in mind if you just start it and let it idle without running it around, it'll idle fine as long as you care to run it. It's not until you take it out and cruise around a little that the problem arises.

    Any ideas?
    Last edited by Squirtcha?; 05-01-2014 at 06:27 PM.

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  3. #2
    Senior Member Skydog's Avatar
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    Sounds heat related, ignition side maybe. I am sure you have done this....plugs....wires... ect...ect... then if u can get a heat temp gun and try to find a colder hole and work from there.
    Good luck
    Last edited by Skydog; 05-01-2014 at 06:33 PM.

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    Senior Member lilrick's Avatar
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    My guess is ignition. I had a circle boat that was doing the same dam thing to me and I swapped out the mag and violla! !!

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    Sure the vent to the gas tank is good ?

  7. #5
    Glendale Arizona Squirtcha?'s Avatar
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    Can't rule out ignition completely, but it should be in pretty good shape. MSD 6AL and the box was tested recently on MSD fixture by a local shop, MSD pro billet dizzy, replaced cap and rotor at the end of last season and no more than a couple hours of run time on it. Relatively new MSD 8mm wires.

    I've got a temp gun and I'm going to take it with next time I run it to see if I can find the cylinder that's going dead. I didn't have it on the last outing.

    As for tank venting, I don't think so but I'll pull the caps next time it starts falling on it's face to see if it helps.

    Is there any way to test hydraulic flat tappet lifters to see if they're bleeding down or otherwise malfunctioining? Can they even cause an intermittent problem like I'm seeing here?

    Due to the nature of the problem this damned thing is almost impossible to duplicate on the trailer which makes it real tough to nail down.
    Last edited by Squirtcha?; 05-02-2014 at 08:26 AM.

  8. #6
    gn7
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    Watch this, and then consider how a BBF oils, the weight of the oil you are running, and what its like HOT.

    Add a little air to the oil, and it only gets worse.





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    Hope you get things sorted out Dan, it's boating weather.

    Sent from my VS980 4G using Tapatalk

  10. #8
    Glendale Arizona Squirtcha?'s Avatar
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    Quote Originally Posted by gn7 View Post
    Watch this, and then consider how a BBF oils, the weight of the oil you are running, and what its like HOT.

    Add a little air to the oil, and it only gets worse.
    You might have to cut to the chase here. Not sure I get it.

  11. #9
    gn7
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    Quote Originally Posted by Squirtcha? View Post
    You might have to cut to the chase here. Not sure I get it.
    Depending on the lifter fit, the weight of the oil, and oil temp, and the volume of the pump, the last lifter in the line could be getting starved at idle.



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    Quote Originally Posted by gn7 View Post
    Watch this, and then consider how a BBF oils, the weight of the oil you are running, and what its like HOT.

    Add a little air to the oil, and it only gets worse.

    Yea buddy where u going with that? Lifter sticking in bore?

  13. #11
    Senior Member Skydog's Avatar
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    Quote Originally Posted by Skydog View Post
    Yea buddy where u going with that? Lifter sticking in bore?
    Oooo got u pumping down losing lift. That would suck!!!

  14. #12
    gn7
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    Quote Originally Posted by Skydog View Post
    Oooo got u pumping down losing lift. That would suck!!!
    More importantly, the further down the line in the lifter gallery you go, the less oil to the lifter.
    Ford pumps are one the best pump in the industry. Titan pumps are patterned after the Ford gerotor pump. But they are the best movers low (idle) speeds.

    Heavy leak combined with low volume/light hot oil can result in low flow at the end of the line.
    On a Ford 460, the mains and rods are being fed by one the lifter galleries. That's a lot of oil demand dependent on the lifters sealing, not leaking to the pan at low RPM.



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    Last edited by gn7; 05-02-2014 at 10:54 AM.

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    Quote Originally Posted by gn7 View Post
    More importantly, the further down the line in the lifter gallery you go, the less oil to the lifter.
    Ford pumps are one the best pump in the industry. Titan pumps are patterned after the Ford gerotor pump. But they are the best movers low (idle) speeds.

    Heavy leak combined with low volume/light hot oil can result in low flow at the end of the line.
    On a Ford 460, the mains and rods are being fed by one the lifter galleries. That's a lot of oil demand dependent on the lifters sealing, not leaking to the pan at low RPM.
    Wow yes thanks for taking me to school again!

  16. #14
    gn7
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    Quote Originally Posted by Skydog View Post
    Wow yes thanks for taking me to school again!
    My post should have said NOT THE BEST MOVERS at low rpm. Makes it more applicable to the problem.



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