Slant Six Forum :: Knock at above idle RPM & sometimes during idle

Actually, that oil pressure is really not that bad for a high mile engine with stock pump and relief spring. If you truly have a rod knock, do this: Pull the plug wires one by one while the engine is running (and be careful to use a thick dry rag or something so you don't get zapped!

). Usually a bad rod will get quiet when you take the fire away from the affected cylinder. You may have to run the engine through several different RPMs with the various plug wires loose to tell the difference.

A fuel pump can make some knocking sounds, too, and believe it or not, old dried out belts sometimes sound like a knock. Spray water on belts and if the sound goes away briefly, that's the source. If it's just a low rumble it could be some piston noise. It's not very likely that the flexplate worked loose if you haven't fooled with it, but that's certainly possible, too.

"DW"

If it sounds like its "deep" in the engine (i.e. bottom end), the rapid knocking when the engine is slowing down after revving is classic symptoms of a rod knock.

Interestingly enough, that was before that heavy grinding noise started, too...

Quote:

Interestingly enough, that was before that heavy grinding noise started, too...

I don't know about the knocking sound, but I'd bet that grinding is the torque converter dust cover rubbing on something.

How many miles are on this engine?
Sounds like it's time for some "dirty work".

Heck, if he wants to pay somebody else to go through it, why not? I sure wouldn't turn him down! Maybe I'm getting older, but if I had the coin you bet I'd pay others to do some of the major work on my car!

Author:	Jopapa [ Fri Aug 15, 2003 5:32 pm ]
Post subject:	Knock at above idle RPM & sometimes during idle
Okay I got the oil press. gauge in and with 20w-50 organic, it holds at 25PSI idle and 40PSI at all speeds above (when warm). I'm confident that both the screen and pump (new pump isn't installed yet) are contributing to the low pressure. BUT, I'm beginning to hear a pretty wicked knock at any speed above idle, and it's even louder when the engine is decelerating. I'm pretty sure it's a bearing going bad, but I wanted to get some other ideas before I say for sure. I know the lifters are making some loud noise themselves too, but this knock is new as of just a few days ago

Author:	Doctor Dodge [ Fri Aug 15, 2003 9:48 pm ]
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How many miles are on this engine? Sounds like it's time for some "dirty work". DD

Author:	Eric W [ Fri Aug 15, 2003 11:02 pm ]
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If it sounds like its "deep" in the engine (i.e. bottom end), the rapid knocking when the engine is slowing down after revving is classic symptoms of a rod knock.

Author:	Pierre [ Fri Aug 15, 2003 11:31 pm ]
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Do yourself a favor, remove the transmission inspection cover and check out the flexplate/torqueconverter bolts. If those are loose you will get a clanking knocking type noise. Its worth the 5 minutes of trouble.

Author:	Eric W [ Sat Aug 16, 2003 12:09 am ]
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Well heck, I should have remembered that one! I had a flex plate break around the bolt head on my old Furys 400. It made more of an annoying ticking noise though that went away above idle.

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Author:	Pierre [ Sat Aug 16, 2003 12:27 am ]
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I mistakingly pulled a freshly rebuilt engine when I heard a loud clanking banging sort of sound coming from it. When I put my hand on the oil pan from underneath it felt like something was banging around in there. Uh-oh. After I had hte head off and everythign was disassembled, ready to pluck, I came to take the torque converter bolts out and low and behold I could turn all of them by hand. When putting in a torque converter make sure the bolt holes aren't stripped before installing.......

Author:	Dennis Weaver [ Sat Aug 16, 2003 1:33 am ]
Post subject:
Actually, that oil pressure is really not that bad for a high mile engine with stock pump and relief spring. If you truly have a rod knock, do this: Pull the plug wires one by one while the engine is running (and be careful to use a thick dry rag or something so you don't get zapped! ). Usually a bad rod will get quiet when you take the fire away from the affected cylinder. You may have to run the engine through several different RPMs with the various plug wires loose to tell the difference. A fuel pump can make some knocking sounds, too, and believe it or not, old dried out belts sometimes sound like a knock. Spray water on belts and if the sound goes away briefly, that's the source. If it's just a low rumble it could be some piston noise. It's not very likely that the flexplate worked loose if you haven't fooled with it, but that's certainly possible, too. "DW"

Author:	Jopapa [ Sat Aug 16, 2003 3:58 am ]
Post subject:
Quote: Actually, that oil pressure is really not that bad for a high mile engine with stock pump and relief spring. If you truly have a rod knock, do this: Pull the plug wires one by one while the engine is running (and be careful to use a thick dry rag or something so you don't get zapped! ). Usually a bad rod will get quiet when you take the fire away from the affected cylinder. You may have to run the engine through several different RPMs with the various plug wires loose to tell the difference. A fuel pump can make some knocking sounds, too, and believe it or not, old dried out belts sometimes sound like a knock. Spray water on belts and if the sound goes away briefly, that's the source. If it's just a low rumble it could be some piston noise. It's not very likely that the flexplate worked loose if you haven't fooled with it, but that's certainly possible, too. "DW" Okay now I know what her dad was doing when he kept pulling the plug wires. I wish he'd actually tell people what he's doing when they ask Yeah the knock didn't change at all when he did it. The engine's only got 75K miles on it, brand new belts, and when I poked around with the stethescope, I couldn't locate the knock at all (though I did hear the occasional loud, electrical sounding SNAP through it which leads me to believe the plug wires are bad). I haven't done anything with the flexplate that I'm aware of. I came close to pulling the inspection cover one day, but had to tighten the bolts back up cause we were running out of time to work on the car and she had to get back home (was working on her car at my place then). Interestingly enough, that was before that heavy grinding noise started, too...

Author:	Jopapa [ Sat Aug 16, 2003 3:59 am ]
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Quote: If it sounds like its "deep" in the engine (i.e. bottom end), the rapid knocking when the engine is slowing down after revving is classic symptoms of a rod knock. Repairable by replacing the bearings I would assume?

Author:	Dennis Weaver [ Sat Aug 16, 2003 9:18 am ]
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Quote: Interestingly enough, that was before that heavy grinding noise started, too... I don't know about the knocking sound, but I'd bet that grinding is the torque converter dust cover rubbing on something. "DW"

Author:	Jopapa [ Sat Aug 16, 2003 11:57 am ]
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Quote: Quote: Interestingly enough, that was before that heavy grinding noise started, too... I don't know about the knocking sound, but I'd bet that grinding is the torque converter dust cover rubbing on something. I had wondered that too, but it only happens in gear, above 35PH, and at slight throttle. If I gas it or let up, no grind. And it's heavy too. Sounds like a deep growl and I can feel it in the gas pedal.

Author:	Jopapa [ Sat Aug 16, 2003 12:48 pm ]
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Quote: How many miles are on this engine? Sounds like it's time for some "dirty work". DD 75K I've been trying to convince her dad of that for quite a while now. And he wants to just take it in and have the block and bottom end components refurbished for 2500 bucks He keeps forgetting that I'm not charging a thing for working on the car, and especially that I'm perfectly capable of doing all the down n' dirty work on the engine

Author:	Eric W [ Sat Aug 16, 2003 9:28 pm ]
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Heck, if he wants to pay somebody else to go through it, why not? I sure wouldn't turn him down! Maybe I'm getting older, but if I had the coin you bet I'd pay others to do some of the major work on my car!

Author:	bud L. [ Sat Aug 16, 2003 9:31 pm ]
Post subject:	?
this may sound like it's coming from left field, but could the cam be walking around with a stretched chain?

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Author:	Jopapa [ Sat Aug 16, 2003 9:35 pm ]
Post subject:
Quote: Heck, if he wants to pay somebody else to go through it, why not? I sure wouldn't turn him down! Maybe I'm getting older, but if I had the coin you bet I'd pay others to do some of the major work on my car! Kind of a pride thing, partially. I'd much rather do the work myself so that I can say "Hey I saved that car". That and having the block overhauled would be a big waste of money. That knock, if it turns out to be a bearing, is the only problem with the block itself. All the other problem areas are in the drivetrain and the lubrication system. He's getting a 70K mile guarantee on an unnecessary repair that he'd be paying 2500 bucks for. I say take half that money and get the cylinder head rebuilt and upgraded (new lifters & pushrods, 340 springs, oversized valves, port/polish, hardened seats, etc). That'd be a BIG benefit to the car, I would think. Then while that's being done I can do the necessary work on the block and drivetrain to fix the other problems, and get & rebuild a Carter BBS to put on (got the kit, just need a carb). And Bud, good idea. After only 75K I don't know how much a stock timing chain would stretch, but it sounds like a simple check to make while the engine's out (if her dad can be convinced to just let me pull the friggin' thing).