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Old 06-17-2006, 09:43 AM
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help 94 351 low compression

my f150 has been blowing oil into the air cleaner. pcv valve and system has been checked and re-placed. engine also has a loud sound like an exhaust leak but exhaust system checks good. engine also misses at low idle but clears up at higher rpm's. compression test shows have thirty pounds on cylinder #8 and 85 pounds on #4. the rest of the cylinders check between 150 and 95. my guess now is possible stuck valve or rings. what do you think? help!

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Old 06-17-2006, 10:40 AM
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Its excessive blowby, bad ring probably timing chain loose and worn maybe jumped one tooth. major bad stuff
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Old 06-17-2006, 03:50 PM
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The writings on the wall, rebuild it before it self distructs.
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Old 06-18-2006, 11:17 AM
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94 351

well it has a sticker on the door saying it had rings and bearings at 142000. its now at156000. I plan to do top end and look at cylinders then. What you think?
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Old 06-18-2006, 06:25 PM
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Take the motor out or just take the heads off and inspect the cylinders, maybe check the valves to make sure there seating properly.
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Old 06-18-2006, 10:00 PM
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Just because it had new rings installed is not fool proof. Things like a ring installed upside down, ring land in the piston not having tne carbon cleaned out, ridge not removed from top of cylinder will break a ring first nturn over, no honing ring will not seat, long list of maybes. Rebuilding all or part of an engine is not just a matter of putting in new parts, surfaces have to be properly prepared or you can be faarther in the hole than when you started. I've seen lots of guys get their bros together to put an engine together and these issues were not followed, and they could have saved themselves a lot of effort by flushing their money down the toilet. And remember, clean work area inside engine is a must, not greasy gritty hands douing the assembly.
I.ve probably done every possible thing wrong that you could do at one time or another, and that is one expensive education. Ask questions and read a lot before undertaking any rebuilding. Some of the articles in the magazines skip over some of these important steps.















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Old 07-18-2006, 03:22 PM
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94 f150

well i rebuilt the haeds and had three burnt valves. cylinders looked ok so i put it back togther. also put in a new timing set old was worn. Engine runs great but still smokes by way of blow by. sucks huh. now i will do bottom end and have a new motor. if this does not fix it i will pour 5 gallons of gas on it and throw a match.
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Old 07-18-2006, 07:23 PM
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you can do an "in the chassis " overhaul, but it probably won't las very long. You will still have a dirty engine both in the valleys etc. but the oil holes will be restricted due to sludge you can't see. Best bet is have the engine out, Vat it twice and have the bores checked, and bore the minumum that will clean up the bores the same size, Check ring end gaps and get the crank mic'ed, and ground if needed and polished for sure. Wharever don't go to a bargain basement shop for the machine work, and use plastigague to double check clearence on the mains and rods. Also let the machine shop install your cam bearings and freeze plugs. One dinged cam bearing can drive you nuts with a floating top end tick. New oil pump and water pump are a must to protect your investment and ALL new filters no matter what it is. Keep dirt and contaminates out, have a happy engine. Get a good book on your engine and make it your Bible and don't listen to guys who have never done it themselves. Good luck.
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Old 07-23-2006, 01:28 PM
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Quote:
Originally Posted by dptyscott
well i rebuilt the haeds and had three burnt valves. cylinders looked ok so i put it back togther. also put in a new timing set old was worn. Engine runs great but still smokes by way of blow by. sucks huh. now i will do bottom end and have a new motor. if this does not fix it i will pour 5 gallons of gas on it and throw a match.

A couple cans of RESTORE liquid overhaul and you could pass the truck off to the next guy.
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