engine knock?
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It's hard to really hear anything on u-tube. It might be piston slap, but the best way to isolate a noise to make sure is a poor boy auto stethescope. Take a piece of re-bar or metal rod and put a piece of fuel line or other hose on it. Put that on the motor in different areas and put the hose to your ear and not only will it be louder closer to the source, but it will also be clearer over the exhaust noise ,fan ect... A long prybar with a plastic handle will work too.
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Senior User
Joined: Apr 2008
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From: Michigan
It's hard to really hear anything on u-tube. It might be piston slap, but the best way to isolate a noise to make sure is a poor boy auto stethescope. Take a piece of re-bar or metal rod and put a piece of fuel line or other hose on it. Put that on the motor in different areas and put the hose to your ear and not only will it be louder closer to the source, but it will also be clearer over the exhaust noise ,fan ect... A long prybar with a plastic handle will work too.
Posting Guru
Joined: Mar 2007
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Really? I didn't know you had torn it down already. Piston slap may be normal for some engines but it's not for an 84. Normal piston slap is a result of the use of forged pistons which have a higher rate of expansion than cast. I am glad that from post one to here you have become so adept at diagnosis that you don't feel the need to take 5 mins. to verify that the knock is not in the bottom end. Or check that the sound is the same in both banks, piston slap should be consistent among all eight. Piston slap should have come on gradually, barely making any noise at first, then getting a little louder over time. Before it got as bad as it is , it should have made noise when cold and not when warm. It will happen to be piston slap untill it throws a rod through the side of the block. Good luck.
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Senior User
Joined: Apr 2008
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From: Michigan
Really? I didn't know you had torn it down already. Piston slap may be normal for some engines but it's not for an 84. Normal piston slap is a result of the use of forged pistons which have a higher rate of expansion than cast. I am glad that from post one to here you have become so adept at diagnosis that you don't feel the need to take 5 mins. to verify that the knock is not in the bottom end. Or check that the sound is the same in both banks, piston slap should be consistent among all eight. Piston slap should have come on gradually, barely making any noise at first, then getting a little louder over time. Before it got as bad as it is , it should have made noise when cold and not when warm. It will happen to be piston slap untill it throws a rod through the side of the block. Good luck.
Logistics Pro
Joined: Jun 2008
Posts: 4,990
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From: Florida
I guarantee it will cost a fortune for a mechanic to do it,and you'd have to go far into the motor to fix it yourself.From what everyone is saying,it isn't anything that will keep it from running good.I wouldn't worry.
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Senior User
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From: Michigan
True, but i absolutely hate the sound.lol
Logistics Pro
Joined: Jun 2008
Posts: 4,990
Likes: 6
From: Florida
Ya oughta come down here and listen to my 300.Better yet go watch one of my vids on youtube where I start the truck up.You'll appreciate the sound alot more.
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Posting Guru
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I'm just not convinced that it is piston slap. Don't you have any place where you could get a mechanic to put a quick ear to it in real life? IF it is piston slap, there is not a lot you can do about anyway, and it may only affect compression and oil usage. But if it's something else....that could be fixed.....but will do damage if it's not.... I would take to a Kwik Lube or something and have them give a quick listen, I doubt they would even charge you. I have had a knock in an engine (long story, not going to get into it) that didn't sound too much different than what I hear on the U-Tube and had as many as 3 proffesional mechanics standing next to it running and unable to pin down the problem. I'll have to admit, I can't think of anything off the top of my head that would sound worse cold, excepting maybe bad lifters, but I've seen more misdiagnosis and wierd stuff both online and in real life to be cautious of any diagnosis that isn't proven nor fixes the problem.
Posting Guru
Joined: Mar 2007
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Low oil pressure would point to a bearing problem, the others wouldn't affect oil pressure.
BTW- What kind of transmission? Auto or standard?
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Senior User
Joined: Apr 2008
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From: Michigan
The oil pressure light doesnt come on...so i am guessing that the oil pressure is fine.
It has the AOD.
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From: Michigan
