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Weird engine trouble
So we took the wife out for a ride. Stopped for an hour, and just as we were leaving the engine started ticking/tapping. Sounded like an exhaust leak, so we drove home easy…
Background, 427 stroker, Big hydro cam, 850 dp, trickflow r manifold. Just recently discovered a bad ground at the battery, and fixed it. Car was cutting out periodically, lug was actually cracked in half…Msd 6al box. Have a spare, swapped it out and no change. Got home and started troubleshooting, discovered that the tick/tap stopped when plug wire 7 was pulled off the distributor. Tried switching pugs and wires no change. There does seem to be a periodic arc at the plug. But insulating the heck out of it by wrapping it in a sliced hose didnt help. Reading the internet i am worried i have a bad rod bearing? Seems strange that it would cause arcing at the plug? I drained the oil, and see nothing in it…havent cut open the filter. Any ideas? Thanks Steve H Spf 1764 |
Pull the pan and stop guessing.
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Big hydro cam
I’d check under valve cover Maybe lifter makes noise only when cylinder pressure is up Do the easy stuff first |
Did that
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Yup
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Yup
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You said you changed the plug AND the lead, and this still happens? Is the sound a "sparking noise" or a "mechanical knock"? Gary |
Check your engine grounds and battery grounds.
Blas |
Grounds
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Its just crazy how its only on one cylinder. Swapped plugs and wires? Absolutely goes away with the #7 wire pulled at the distributor. Oil is clean. |
I'm not big on coincidences, so when a new problem arises right after I've done work on a car, I suspect I unknowingly did something while doing the previous work. And electricity takes the path of least resistance, so the arcing tells me there is too much resistance where the electricity is supposed to be going. If it were me I'd start by adding some temporary jumper cables to know the engine and ignition are properly grounded to see if that caused the arcing to stop. If so, I'd start looking for the bad connection(s).
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Agree
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Why just this one plug? All one cylinder head? Was thinking maybe ill run a ground wire directly from the cylinder head? Think there are tapped 7/16-14 holes i could bolt a cable to. For the life of me i just dont understand how the header could be more grounded than the engine. The engine ground looks and feels good, but maybe the next step is to remove it and clean it good… |
You don't have to use a full size battery jumper cable to test things. A long 12 gauge wire with alligator clips will do.
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Did you check for a broken valve spring?
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A mechanical "ticking, tapping sound" where there was none previously does not have an electrical origin; it has a mechanical origin. You can check all the various it isn't that bad sorts of non-mechanical origins possible. When you are all done, the odds are your mechanical "ticking, tapping sound" will have a mechanical origin.
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I had a 65 t bird come into my shop 2 weeks ago with the same sound your describing and went away when plug wire disconnected, dropped the pan removed number 5 rod cap and bearing was gone didn't see anything bad in the oil. I hope I'm wrong but I have seen and heard this problem before.
BTW oil pressure was good. Joey.S |
My $0.02.
Joey.S brought the potential of a rod bearing. Let's follow that. If pulling a plug wire eliminated the ignition (kaboom) in #7, perhaps that stopped the rod from pushing down on the crank journal - the tick. Now without the ignition in the #7 cylinder the crank is pulling the rod rather than the normal of having the piston push on the rod. Hope this makes sense, sorta does to me. Otherwise just ignore my WAG. I'd look at a lot before pulling the pan, yup a PITA with the SPF/Canton combination. Been there done that, I didn't like it either. Jim |
Perhaps one of those tiny cameras would allow you to take a peek without dropping the pan.
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Tommy, exc. idea, we had the same type issue, bought Steve's (Back in Black) West Coast Cobra, pulled the dip stick (Nothing but the top of it :eek:) Brent took his camera though the drain plug, to see if the rest of it was in the oil pan, thankfully it was not there :p That camera saved us pulling the pan. Cheers Tom.
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Unless the tiny camera has a way to remove the rod cap you will not be able to inspect the rod bearing or the crank journal.
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How about a video? That would help other eyes for diagnosis. A suspect bad rod bearing AND a sparking issue DOES NOT HAPPEN AT THE SAME TIME. |
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