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Discussion Starter #1
My Caprice has started making an odd whooshing / rubbing noise. It's noticeable at idle and when cruising. (I doubt it goes away when I driving hard--it's probably just not audible.)

I held a mechanic's stethoscope up to the alternator, the AC compressor, the water pump, and the tensioner, and none of them seemed to be the culprit. I didn't see any way to listen to the idler pulley as the whole thing seemed to be spinning. (Maybe I was mistaken.) Same goes for the crank pulley.

Have a listen in this video and let me know what you think.

 

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I Listened twice

I get the whoosing - that's normal with many open air cleaner and I got that noise on both my cars.

That 'KNOCK' on the other hand is nowhere close to a 'rubbing' to me. Sounds more like detonation. Or cracked flexplate? Fried belt tensioner?

Maybe you can reshoot the vid to weed that noise out and get to the rubbing sound more?

in any case still interested what that knock is.
 

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Sounds like a loose part is rubbing against a spinning part. Perhaps the AC compressor clutch plate is rubbing against the pulley/hub. Does the sound go away (or get worse) when you turn on the AC?
 

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Sounds like the same noise my wife's car made just before it spit the A/C compressor clutch plate off the front! My guess is A/C Compressor.


Mike--94MSP9C1
 

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Discussion Starter #6 (Edited)
Good news (not good news). Apparently great minds think alike, as I had the same idea as BALLSS suggested. I had the belt off to replace the alternator tonight, so I fired up the engine. The noise persisted.

Sigh.

I can't help but think that my hope was misguided, and the douchebag who rebuilt the bottom end has fscked me yet again.

The noise didn't start until after a 600-mile drive, cruising at 90+mph and 3000ish RPM (4.10 gears). Oil pressure was steady around 60 PSI (high-volume oil pump, running Mobil1 0W40), and coolant temp never got over 175 or so (160* stat, fresh Dexcool coolant, with water wetter).

One of these nights, I'll put it up on ramps and listen to the underside of the engine with my stethoscope and see if I can hear anything. But, at this point, I feel like I'm just gonna drive it until whatever is making that noise goes completely.
 

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The noise didn't start until after a 600-mile drive, cruising at 90+mph and 3000ish RPM (4.10 gears). Oil pressure was steady around 60 PSI (high-volume oil pump, running Mobil1 0W40).

You know it is possible to suck a stock oil pan dry of oil running that speed for a long time and the high volume pump. Possibly you had oil starvation from too much oil being up in the heads and not enough down in the pan!


Mike--94MSP9C1
 

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You know it is possible to suck a stock oil pan dry of oil running that speed for a long time and the high volume pump. Possibly you had oil starvation from too much oil being up in the heads and not enough down in the pan!


Mike--94MSP9C1
...beyond internet rumor....you have documented proof this happens with a HV pump?

There are thousands of HV pump SBC, mine being one of them, and any sustained WOT 6k rpm (100's of 1/4 mi passes) has NEVER seen a drop in oil pressure or oil starvation for me. 3k rpm the motor will run all day with standard or HV oil pump. Op reported good oil pressure during his sustained 3k RPM drive

Not saying Op's issue is not a fading bearing but good oil pressure is a better sign than not the noise is something else.

It could be as simple as a Opti rotor rubbing cap....more diagnostic will need to be done which may involve engine tear down but a HV oil pump sucking pan dry of oil would not be on my list.
 

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Discussion Starter #9
You know it is possible to suck a stock oil pan dry of oil running that speed for a long time and the high volume pump. Possibly you had oil starvation from too much oil being up in the heads and not enough down in the pan!
If the motor was oil starved, wouldn't it have manifested as occasional low/no pressure on the oil pressure gauge? (I have an F-body cluster with the right sender / resistor so that it shows actual oil pressure.) I kept a close eye on the gauges the whole way and oil pressure never wavered from ~60 psi while cruising.

I've got 4200 miles on the oil and will be doing an oil change and sending a sample off to Blackstone at 5000 miles, so if there's any internal wear issues, I should find out about them then.
 

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Discussion Starter #10
Not saying Op's issue is not a fading bearing but good oil pressure is a better sign than not the noise is something else.

It could be as simple as a Opti rotor rubbing cap....more diagnostic will need to be done which may involve engine tear down but a HV oil pump sucking pan dry of oil would not be on my list.
Whew, that makes me feel a little better.

I did replace the Opti fewer than 2000 miles ago because I thought it was causing a misfire--turns out that the issue was actually a dirty lead on the coil itself. Once cleaned, the misfire has been banished. I used an AIP Opti from Amazon. https://www.amazon.com/gp/product/B00ARJO1TA/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I'll stick my stethoscope up to the Opti and see if that's where the sound is coming from.
 

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You know it is possible to suck a stock oil pan dry of oil running that speed for a long time and the high volume pump. Possibly you had oil starvation from too much oil being up in the heads and not enough down in the pan!
I've read a lot about this happening, but I've yet to see anything outside of full-on drag cars experiencing this with high-g hooks. It just does not happen to a street car.
 

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sustained 60 psi oil pressure clearly indicates the oil pan did not get "sucked dry"...and IMHO that does not happen anyway with a HV pump. a empty oil pan=zero oil pressure

Does not mean a bearing or wrist pin or something "internal" to the engine isn't going on but solid and steady oil pressure is a good sign of bearing condition. Doesn't mean a bearing didn't go but still is a good sign if oil pressure is good

pulling the belt just identified the noise is not coming from one of the belt driven accessories.

Maybe the impeller of the WP if failing...as another example beyond a rotor/cap thing as a possibility

point is you just need to dig deeper to find the "why". Using a stethoscope will help

....and yeah you may need to dig "into" motor but more through external inspection and looking at your oil, cutting open filter, sending oil out for analysis are all things to do if initial visuals and sound do not identify the sound source
 

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As someone that JUST went through this last week, **** happens. My engine was built by Karl Ellwein and was an absolutely top notch build with 5k or less on it. The engine was babied from the get-go, and developed a knock only present on the interstate at light throttle acceleration. Clean oil, but cutting open the filter showed signs of a bearing going south. Oil pressure never got low or fluctuated. To this day, the car holds 30psi hot, in drive, 42 psi hot in neutral. Karl has no idea what went wrong other than to say that sometimes stuff just breaks.

Pull the stick and look for metal. Pull the filter, cut it open, and look for metal. Get a stethescope and listen around for the source. If it is louder from the block or pan - well, then you start figuring out next steps. I'd advise not driving it until you find out what is going on. Driving on bearings that are degrading but still functional will lead to much larger and more expensive issues downrange.
 

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That noise does NOT sound like a spun bearing on the rotating assembly, and seems like it's more in sync with the cam than the crank. If it's not the opti or the WP, then perhaps it has something to do with the cam or valve train. Just sounds more like something is rubbing than a sticky bearing.
 

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sustained 60 psi oil pressure clearly indicates the oil pan did not get "sucked dry"...and IMHO that does not happen anyway with a HV pump. a empty oil pan=zero oil pressure

And exactly what background to you have to base this opinion on? I based it on the advice of a man who builds motors for Million dollar race cars and he advised me NEVER to use a high VOLUME pump on a stock motor as it can pump the oil out of the pan faster than it can return on a stock pan. The pressure would not drop to zero but fluctuate as the oil returns to the pan so you would still have pressure but it can starve the bearings needlessly!


Mike--94MSP9C1
 

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I've read a lot about this happening, but I've yet to see anything outside of full-on drag cars experiencing this with high-g hooks. It just does not happen to a street car.

It can happen on a street car using a High Volume Pump (NOT High Pressure) on a Stock Motor with a stock pan. It is possible to pump the oil out of the pan faster that it can return and I have seen first hand the results of it happening on sustained high rpm running so Please do not tell me it can't happen!


Mike--94MSP9C1
 

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And exactly what background to you have to base this opinion on? I based it on the advice of a man who builds motors for Million dollar race cars and he advised me NEVER to use a high VOLUME pump on a stock motor as it can pump the oil out of the pan faster than it can return on a stock pan. The pressure would not drop to zero but fluctuate as the oil returns to the pan so you would still have pressure but it can starve the bearings needlessly!


Mike--94MSP9C1
Mike

My background is I have a HV pump and in 40k mi on this motor I have NEVER seen oil pressure fluctuate in any kind of use. Stock pan and windage tray. And no my oil pump drive gear is not wearing out either

I agree a HV pump should NEVER be used in a STOCK motor. Not because of pans getting sucked dry but because HV pumps are for motors built with wider bearing clearances and all the holes in crank have been chamfered.

What can create oil starvation is motors built (often 383/396) using stock or aftermarket oil pans is NOT installing the windage tray because of rod bolt interference. In autox applications this can be a huge problem as oil will foam and oil starvation can happen without a windage tray. Nothing to do about whether a HV, standard or HP pump is used. Very simple to run windge tray in stroker motors by simply standing the tray 1/8" away from rotating assembly using a washer between the extended main cap studs for the windage tray and nut

Your builder friend may be extremely qualified and build motors worth 100's of thousands of $ but I have never seen or heard of anyone sucking the oil pan dry from using a HV pump in a motor set up to use one (let alone of it happening in any street car). Just people who have never used one passing on 2nd hand hearsay
 

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Discussions about high volume pumps can get so contentious. But unless the volume was increased substantially, and the engine wasn't built for it (loose bearings, oil coolers, low viscosity oil), then it should be OK. The worst that will happen, esp at 3,000 RPM (not considered high) is that the oil gets hotter than it would have with a standard volume pump.

Speaking of the pump, although it seems unlikely, perhaps that is the source of the noise.

I use a Moroso pump that is a Melling Select high pressure pump, and it has a distinct wine (but nothing like the noise here).
 

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I have never seen or heard of anyone sucking the oil pan dry from using a HV pump in a motor set up to use one (let alone of it happening in any street car). Just people who have never used one passing on 2nd hand hearsay

I am only going to say this one last time! I PERSONALLY scattered my motor all over the freeway at over 158 mph and was told by the highly qualified engine builder that I had sucked the pan dry and that caused it to spin a bearing and throw a rod out the side of the block. PLEASE stop talking to me like I am a google kid and not someone who has been there and done that!!!!!


Mike--94MSP9C1
 
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