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06-19-2019, 05:50 AM | #21 |
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Re: Mystery Missfire
I come back to an intake leak. A cracked intake manifold can be hard to find. Good luck and let us know what you find.
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06-19-2019, 01:32 PM | #22 |
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Join Date: May 2010
Posts: 1,304
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Re: Mystery Missfire
1001H prompted a train of thought and I removed no4 plug and started the engine and let it idle on 3 cylinders . Took a compression with the running engine and got a steady 40 PSI VOILA !!! Problem revealed my guess that tight valve clearance on the inlet valve . Checked the PSI on cranking and got 75 PSI . The earlier 65 PSI I got I forgot to open the throttle fully . So here is hoping that the engine has adjustable lifters I have never had the cover off but knowing my luck I guess it is a head off job . I will keep you all informed ,stay tuned !!!
John in heavy rain Suffolk County England/ |
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06-19-2019, 03:00 PM | #23 |
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Join Date: May 2016
Location: Scottsdale, Arizona
Posts: 612
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Re: Mystery Missfire
Good Luck, John...Ernie in Arizona
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06-19-2019, 11:40 PM | #24 |
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Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
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Re: Mystery Missfire
If you have a sticky valve, then I'd add a can of Sea Foam to the gas, and another can to the oil.
In less than 5 miles a can of Sea Foam in the oil made my clicking Olds engine sound like new. This was back in the 80's on a Cutlass with a sticking hydraulic lifter. |
06-20-2019, 02:31 PM | #25 |
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Join Date: Dec 2011
Location: SW Idaho
Posts: 970
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Re: Mystery Missfire
The needle bouncing steadily leans toward tight lash. Erratic bounce, sticking guide, weak or broken spring. Sloppy stem clearance and washed out cam lobe might be a steady but low reading. Compression test-wet&dry, vacuum test readings, cylinder leakage test and lastly this vacuum gauge sans check valve if needed is about as much help as a fella can get. Good luck. One thing we do know, valves won't stick closed over night. They can bounce, leak, wobble and dance or stay open. Then there are rings but that ought to be consistently low, not intermittant. Sorta like herding cats.
Last edited by 100IH; 06-20-2019 at 03:02 PM. |
06-21-2019, 12:49 PM | #26 |
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Join Date: May 2010
Posts: 1,304
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Re: Mystery Missfire
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John in partly cloudy high pressure on the way Suffolk County England . |
06-22-2019, 01:08 PM | #27 |
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Join Date: Dec 2011
Location: SW Idaho
Posts: 970
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Re: Mystery Missfire
This is a model A. There isn't anything that hasen't been done. Obviously it did not have adjustable lifters. Think I might try the same. File might not touch it due to hardness, got nothing to loose XX.
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06-22-2019, 01:29 PM | #28 |
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Join Date: Aug 2010
Posts: 260
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Re: Mystery Missfire
John, I've done this, take a small rag like a piece of an athletic sock or towel, soak in motor oil, rap around lifter base, it will catch and hold the filings. Buy a new file it will cut with no problem.
carry on nick c |
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