351w knoccking
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Junior User
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From: anchorage
351w knoccking
i bought a used 351w unknown back ground, no sounds when cold but when starts to warm up, has a load or no load off the gas no sounds. but when part throttle light load, knocking and a steady speed. adjusted valves 50 times
still the sond is there. has a cam in it ,rpm manifold ported a polished heads.gas doesnt matter or timing?b dont really know were to start
still the sond is there. has a cam in it ,rpm manifold ported a polished heads.gas doesnt matter or timing?b dont really know were to start
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Does it sound like a deep knock as if you were to tap your knuckle against a hard piece of wood, steady and constant? Does the sound come on around 2200rpm +/- and go away under that rpm? Could be a spun bearing, or rod knocking.
Does the sound kinda mimic the sound of a rock in a glass bottle when you shake the bottle?
Does the sound kinda mimic the sound of a rock in a glass bottle when you shake the bottle?
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if it is rattlin when it warms up the bearings are probaly shot. i bought a junkyard 5.0 and it rand good b/c it was a repo and a friend worked there, thought it was a good deal so i installed it, first time i took it down the highway it was rattlin under load a bit, and it got progressively worse, til it was all out bad and had no oil pressure. after i rebuilt that motor mine did the same thing a month down the road where it rattled pretty good at a constant 3000, i thought it was a spun bearing, but after the piston fell out the side of the blocki found it was a weak n loosened rod bolt that un did itself, possibally from a overtorque, 302 only need 25 lbs. small weak azt bolts. i like the 351 b/c it has bigger bolts all around,
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From: anchorage
when its cold and have 0w30 oil. i still have about 50 lbs. of pressure and when hot it will go to about 15 -20 hot with the thin oil. the rpm does not matter when hot ,i could go 10 mph light constant or 85 light constant throttle off the gas and its gone or on the the gas its gone. ive also put striaght40 weight oil in it and it still does the same thing
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Have you double checked the rocker adjustment? Do you happen to know if the valvetrain is adjustable? Has it always done this? Well it is either a rod, some people check the rods by unhooking one spark plug at a time (idleing in park) and if it stops knocking then its the rod if not then maybe you should make sure the rockers are adjusted properly. Just trying to throw some things out there, later
Last edited by jwtaylor; Oct 10, 2003 at 08:34 PM.
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Lead Driver
Joined: Feb 2003
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From: Oak Harbor, OH
Check your timing against the timing specs of the cam. If all else fails set it to 10 degrees btdc and then retard as neccesary to get rid of the "ping" a lean condition can cause this as well.
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if the oil pressure is dropping the thin oil is escaping through the bearings, even at operating temp it should have a good 40 lbs? i guess. i would have guessed sticky lifter otherwise, the valvetrain isny adjustable in these, if a rocker or pushrod is worn it has to be replaced with new or something like that, dont know too much about it if they r worn. another deeper rattle could be anything from piston to wristpin, it usually takes a trained ear with experience to tell the difference. a piston will usually be under acceleration or load though, where a bearing is usually constant. also had a timing chain once that rubbed against the cover but it did it even when cold and it was intermittent.
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From: anchorage
it does have adjustable valve train ive done that about 50 time and no different. i just adjusted thee timing to the highest vacuum and the starter stall tests . this does the sound all the time when hot. it was about 25 degrees today heree anchorage,ak . has a 180 degrees t stat and going to change to a 195degree .had the intake off very clean insides. also been runnig hi test for a week. i know the sound of ping. ive had the truck for about a year now and driving it as my driver need help