What's going wrong inside my 350?
 

Purchased the truck back in Nov of 2016 as a partial finished build. Link to unfinised build thread below. I stopped updating the thread because of photobucket.

http://67-72chevytrucks.com/vboard/s...d.php?t=723325

Engine is a 1978 Fresh rebuilt chevrolet 350 with .030" bore over and mild cam. Has a 700r4 corvette servo, Stage 2 shift kit, Beast sun shell 3000 Stall converter &
B&M Unimatic Shifter as I was told.

I've started the truck maybe half a dozen times since about september and there were no issues except for the timing and carb calibration needing done and it being loud as HELL. On December 19 I trailered it to the exchaust shop to have the exhaust installed because of good weather. I didnt think I was going to be able to get it done until spring so it put me one step closer to get it on the road come spring.

Since the truck is in pretty poor timing and the carb needing tuned the truck was winched up onto the trailer. Unloaded using the winch at the exchaust shop, pushed into the shop, pushed out of the shop and winched back up onto the trailer and towed home.

When I got the truck home we decided to try and start the truck to hear how the new exhaust sounded. Well that opened another can of worms b/c I was pissing transmission fluid out one of the hoses on the passenger side of the transmission. After some further investigation that just turned out to be a loose hose connection. After a couple more starts the truck starts to make this hell of a screaming noise coming from the bottom end of the engine. I pulled the alternator and belt off and tried it again. Same noise so it's not coming from the water pump or alternator.

After investigating around underneith the truck to try figure out what the noise was, I found the torque converter wasnt even bolted to the flex plate. WTF? I could spin it freely with my hand. I figured this had to be the problem maybe the snout of the torque converter was rubbing up against the flex plate making the noise. So I went to my local transmission shop which happens to be located next to the exhaust shop and got the three missing bolts at $5each.

I installed the bolts into the torque converter and got the bolts torqued to spec. I figured this would now fix the squeeling noise & vibration and it didnt. So I re-installed the alternator and belt because I know they were good. I started to do some googling and youtubeing and found that 'maybe' it might be due to vacuum inside the block. So I pulled the PVC valve out of the valve cover and the breather on the passenger side and proceeded to try and start the truck again. Same noise. Either then the timing being off and carb needing tuned I'm not sure what is going on inside the block. Here is an example why I gave this a try.

https://www.youtube.com/watch?v=M5eEitHdsXc

I did tons of searching from flex plate failure, engine knock, bottom end failure, rear seal replacement, harmonic balancer replacement and cant find anything simular to what I'm experiencing. So here I am posting to find out if anyone might know possibly what might be going on. It doesnt make sense since each time I've started the truck before it just ran rough because of timing/carb calibration.

Since this was a partial finished build I'm thinking the guy B.S'd me into thinking this was a rebuilt engine and tranny. I'm not saying it's not, but now this happens. It's weird because I'm getting real good oil pressure on my gauge. I've yet to pull out my compression tester to check the cynlinders. Any insite on what might be going on would be much appriciated. I'm hoping that I dont have to pull the motor & tranny. I paid top dollar for the truck because of the work completed and was told it was a frech rebuild.

I took two videos today and posted them to the link below. I also included the first startup video that I took back in September. Hopefully the shared links work. Thank you everyone for your time.

September first start & Top Engine noise from the top
https://photos.app.goo.gl/EAqnZqKHPN5WNPZW6

Under Truck Torque Converter flex plate.
https://photos.app.goo.gl/qUP6BQRNsuhLtN427

Re: What's going wrong inside my 350?
 

Since I can't get videos to play I'll take a stab at it...is the bendix releasing?

Ok I got last video to play...sounds like the bedix... starter may need shimming...(my guess)

Re: What's going wrong inside my 350?
 

Yes I believe it's disengaging properly. When I was under the truck I didn't see it engaged against the fly wheel when the truck wasn't running. I was a little hesitant climbing all the way under there when the truck was running. This noise is coming from the block/crank area but you might be on to something. I will need to check it out further to see if that is the case. If that is the case why would this just start to happen? Wouldn't it pretty much burn out the starter right away? The noise does not appear to be coming from the starter side of the motor as far as I can remember. Possible bad flex plate?

Re: What's going wrong inside my 350?
 

Dose sound like starter drive hanging up. Did you check trans oil if ok. If you take a heater hose or any small hose and put it at diffrent spots on the area with the other end to your ear you should be able to tell where the noise is coming from. Acts like a stetascope.

Re: What's going wrong inside my 350?
 

Buy a cheap stethoscope from Harbor Freight, or simply put a piece of rubber fuel line up to your ear and you will easily be able to isolate the offending noise.

Re: What's going wrong inside my 350?
 

That's an interesting sound. Does it do it as soon as the engine is started? Is it louder toward the front or rear of the engine? Can you hear it during cranking if the coil is disabled? Is cranking speed normal?

It sounds like a bearing and it could be on the crank. If a rod bearing has spun slightly and is wedged against the crank the oil hole from crank to bearing can become restricted which keeps the oil pressure from dropping.

It's also possible a timing cover is touching the balancer or that there's something wedged against the oil pump drive but those sounds are usually different. The balancer noise is a bit tinnier and the oil pump drive isn't as loud. But the problem with a video is it's hard to get relative sound levels.

But I have heard a strange squealing before that can sound very bad but is actually easy to cure. If the PCV valve is doing its job and drawing air out of the crankcase but there is no way for air to enter the crankcase, air will begin to flow past the main seals. It is very loud. This happened in one case because a set of cheap chrome valve covers came with grommets that weren't actually opened so the breather could not pass air into the engine. In another case an individual installed a PCV vavle in each valve cover not knowing one needed to be vented. In both cases the noise started several seconds after engine start. If you suspect this may be a problem, the easiest check is to ensure the crankcase is vented, possibly by pulling the PCV valve while the engine is running.

Also, mild cam plus 3000 stall converter??? That may not give you the performance you want. But it may not be an issue...

Re: What's going wrong inside my 350?
 

I've become a bit of a skeptic over the years as I have come to believe that you can't call an engine "rebuilt" unless you see the receipt from the machine shop for the engine work and the receipts for the parts that are supposed to be inside of it.

I've seen too many guys selling "rebuilt" engines around here that had a quickie valve job, a ball hone job and a trip to the car wash to wash them up before being reassembled with a low buck ring and bearing kit. Nothing wrong with that if you are putting a driver motor together for yourself but it is false advertising if you are selling the engine as rebuilt.

Right now it boils down to check everything just as if you had pulled the engine off a stand and installed it yourself. Check for what else they didn't do right or didn't finish. Don't assume anything except that you need to check everything.

Re: What's going wrong inside my 350?
 

I would drain the oil to see if it's clean
also what type of filter is on this Engine if it is orange (fram) I would have conerns
Because No rebuilder would use a fram unless they were on a low buget

Re: What's going wrong inside my 350?
 

I will have to check the starter and see if its hanging up but unfortunately keeping the truck running and filming video is a two person job until i can get some help.

Its a god awful noise that seems to be resonating right through the crank out the front of the motor. I looked at the teeth on the flex plate and there is no wear or worn teeth.

Thank you for the suggestion.

Re: What's going wrong inside my 350?
 

Will do. I have some spare hose.

Re: What's going wrong inside my 350?
 

-Yes it does it as soon as the engine is started.
-its hard to tell if its louder towards the front or rear of the engine but i would suspect the rear of the engine as in the video.
-engine cranking appears to be normal.
- I pulled the pcv valve on the drivers side and the vent on the passenger side to open things up just in case there was a venting issue. Same results.
-ill investigate the spun rod bearing and see if i can figure out what is happening. i hope to god its not a spun rod bearing. There doesn't appear to be any banging/tapping during idle just the squealing heard in the videos.


Thank you for your input.

Re: What's going wrong inside my 350?
 

mr48chev,

I've taken your advise on this before and if you dont check every nut and bolt yourself then you don't know its right. As I mentioned in my post above there was no bolts in the torque convert to the flex plate. I've come across many WTF moments in this build. You can only count on yourself to make sure its done right the first time.

Re: What's going wrong inside my 350?
 

I did check the oil today and its clean as day. Yes I put a frame filter on it when I changed the oil.

Re: What's going wrong inside my 350?
 

The high pitch squeal on the you-tube video is concerning, sounds like a spun bearing, or some sort of metal on metal.

The flex-plate video, I didnt' hear the squeal, but sounded like the starter hanging up.

1) I know there were some alignment issues with GM starters.

2) I've seen the center broken out or flex-plates. Everything appeared normal until dis-assembled.

3) Did the torque convertor get seated properly? May be an issue with your front pump.

Re: What's going wrong inside my 350?
 

You might check out the flex plate for a crack, and make sure it's bolts are tight.

Re: What's going wrong inside my 350?
 

I'm with Mr 48chevy pull the motor and start over

Re: What's going wrong inside my 350?
 

What's the oil pressure? Since someone was into the transmission as well - installing significant mods - I would do a pressure test, then pull the pan and look for shavings at the trans filter. An easier test might be to send a sample of trans fluid and engine oil to somebody like Amsoil:


https://www.amsoil.com/shop/by-produ...ysis-services/

Whatever you do, isolate the problem to either the engine or the transmission before you start pulling the truck apart. Just sayin'...

Re: What's going wrong inside my 350?
 

When I get a chance I will check to see if the starter is getting hung up. I'm hoping that is the problem.

What are the symptoms of a spun bearing either then grinding/squealing?

I havent checked the flex plate yet. that would require removing the transmission.

When you say front pump? Do you mean the water pump? I disconnected the belt from the motor and turned it over to the same sounds.

Re: What's going wrong inside my 350?
 

After I check to see if the starter is hanging up I'll probably go this route to check the flex plate. If the starter is hanging up would it still be engaged to the flex plate when the ignition is not on? When i looked at it with the truck turned off I couldnt see the bendix engaged to the flex plate. So I'm assuming its functioning correctly. Unless once the ignition is turned it keeps on engaging against the flex plate until the motor shuts down.

I'm not sure.

Re: What's going wrong inside my 350?
 

The oil pressure on my gauge is reading about 55-60 PSI on idle. it's hard to get an accurate reading because the timing/carb tuning is all off and trying to get it to run smoothly is a challenge to get an accurate reading.

I will be checking out the starter just in case it's hanging up then probably look at the flex plate. Then if anything else then compression test and hopefully it's not something in the motor. Last thing I need right now is to replace the engine.

Re: What's going wrong inside my 350?
 

I'm hoping that I don't have to do that. And of course I have no recourse because the truck was sold as is/where is. I paid more then I would have if it didn't have all the 'work' done to it, which was probably under false pretense. It makes me so upset I have a pain in my gut. Could I go after him? it's been like 2 years now.

Re: What's going wrong inside my 350?
 

-remove the engine oil filter and cut it apart with a good utility knife (or filter cutter) to check for anything metallic in the filter medium. while it is off check the filter adapter and bypass valve to ensure it is all bolted up correctly and the bypass is operational and not causing a squeal. if in doubt simply replace the adapter since they are fairly cheap anyway. like mentioned in an earlier post you could send out an oil sample but that is a bit spendy and takes time. anything major will have caused something to show up in the filter so this would be considered a preliminary check before doing that. if metallics are found then pulling the engine apart would be the next step. also, like said, use a good quality filter, especially on a new engine, to trap as much debris and new engine break in metalics as possible. personally I would not use a Fram filter on my lawnmower but that is just me. some will use a cheap filter on new engines because they feel it is expensive to put a good filter on and then simply swap it out right away after a few runs or hours on the engine. to me that is reverse thinking and I would use the best filter I could on a new engine because that is when you know there will be fluff from shop rags, dust and dirt from the rebuild process etc. and that is when you need the best filter you can get. just me being me though
-ensure you have end play in the crankshaft since no end play could also make the thrust bearing work overtime and possibly make noise
-check for any vac leaks that may cause a whistle. look around the base of the carb to ensure any and all vac ports are used or capped and there are no cracked hoses or leaking vacuum actuators like a trans modulator hose/tube/valve. check the brake booster manifold fitting, hose, check valve. carb base gasket etc. pinched modulator hose or tube at the bell housing to engine flange (hey, it happens).
-check to ensure there isn't a timing tab rubbing on a pulley, check the pulleys to ensure any bolt on pulleys or accy are tight and fitting correctly. look for any odd rub marks on anything up front. look at the vibration damper and check for movement of the outer ring. a quick marker line across the two parts will show any movement after the engine has run and been shut down. squished out or deformed rubber in the damper joint of the 2 parts is usually an indicator of a possible problem or future problem. I have seen some of these parts "cleaned" improperly using solvents that attack the rubber ans cause the 2 parts to move/separate
-check for any odd heat marks or paint discoloration on the timing cover that may indicate an issue with a loose timing component or wrong fastener used inside there
-check the valve covers to ensure they are installed correctly. if installed incorrectly the rockers can rub on the covers. if not too inconvenient you could also remove a cover and check to ensure the top end is getting oiled properly and everything looks like it should
-check mechanical fuel pump and/or pushrod for issues. the pushrod could be "held' with a bolt in the front area of the engine if there is a bolt used there that is slightly too long. this would likely cause the pump not to operate but it only takes a sec to check anyway
-run the engine and use a stethoscope with an open hose around the base of the carb and top/front engine area to eliminate this area. check the distributor as well because a bad distributor shaft bushing could make a similar noise or a ruptured vac advance diaphragm may whistle. the same goes for a trans shift modulator valve
-jack the truck up high enough and block it to safely work under the truck if the engine were running. try to keep the angle of the truck the same as when it sits on the ground so you have the best chance of reproducing the noise
-remove the torque converter cover and look inside it for any metallic dust or other tell tale signs.
-remove the vac line at the shift modulator and look for fluid inside the hose that may indicate a ruptured diaphragm. ensure the metal vac tube (if equipped) is in good condition and doesn't have a torn off mounting bracket that could cause a whistle through the spot weld holes on the tube
-look up inside the bell housing at the starter drive and flywheel tooth contact area. check deep into the teeth to see if these parts have been bottoming out during contact. a quick spray with some paint in the tooth area would show the contact pattern after the starter was used. small block chevies usually need a few shims and some trial and error to get the starter drive to contact the flywheel correctly. they may just not sound right or they may engage and stay engaged if not shimmed properly. a starter that stays engaged will make noise and may fly apart when the engine is revved. this is due to the rpm the starter is forced to work at when the engine revvs up plus the crude drive tooth engagement would make noise at rpm. you could also remove the starter and physically check it out. if you disconnect power to the distributor you could use a remote starter switch or some other method (like a buddy in the cab) to crank the engine while you watch how the starter is working to ensure there is no problem there.
-check to ensure the torque converter is slid all the way into the crankshaft. since the engine was ran without the torque bolted in the snout of the torque or the end of the crankshaft may have been slightly damaged so they may not have been able to slide fully into the together. this would mean the flex plate would be required to take up the slack by flexxing or becoming slightly bell shaped. this may cause a harmonic when running. when unbolting the torque the 2 parts should be able to be slid together without having to be pulled in with the bolts. the torque should also be easily slid into and out of the crankshaft. when pushed back into the trans there is also a dimension as to how far the torque is allowed to be pulled out of the trans to bolt up to the flex plate. too much dimension here would mean the torque is not fully engaged in the trans pump correctly. not enough dimension could also be a problem. since the trans and engine were apart and you didn't do the work you are coming into it with no history as far as what was done or if the torque is the correct one etc
-check the front of the torque to ensure there was no damage that may cause interference of the internal converter moving parts with the "dent" in the converter shell or a distorted fastener mounting flange, if any dents or distortion are present.
-check to ensure a torque drain plug (if equipped) was/is positioned so it lines up with a hole in the flex plate. if not the flex pate could be distorted causing the harmonic.
-check to ensure all the flex plate to crankshaft bolts tightened down correctly and fully. we assume the correct length bolts were used. cracks in the flex plate are common around the mounting flange to the crankshaft
-check the flex plate for cracks all the way around the crank flange and also around the torque mounting areas. turn the engine by hand and check the whole way around. look for metal powder anywhere and also flex the flexplate as you go and listen for the sound of metal moving on metal as would be heard if there were a crack. check to ensure the flex plate was installed the correct way around and not backwards. these checks in this area can be hard to do but could be made easier if you placed some long bolts in the trans bell housing to engine mounts and use them as line up pins to slide the trans back enough to see into the area. that way ir could be easily slid back together after and wouldn't require support (that would be in your way) while slid back
-check to ensure the flex plate to torque mounting bolts are the correct length and did not cause a dent or distortion of the torque shell that, again, may cause interference with the internal converter moving parts
-check to ensure you have the correct converter for your trans (hey, it happens)
-if these things all look good then bolt everything back up carefully except leave the converter cover off. install a new oil filter and top up the fluid
-start the engine and slide under (carefully, ensuring no loose clothing etc) and use your stethoscope to try to pinpoint the area where the noise is coming from. use the open hose at first and then the probe rod to be more specific. I highly recommend a stethoscope because it deadens ambient noise so you can zero in on a particular area. be aware that the hose can also get snagged on moving parts. what I have done is grab a scope that has the ability to replace the hose with a longer hose so I can be physically further away from moving parts.
-check for exhaust system whistles which can be caused by welds that have slag inside the pipe unseen from the outside or poor pipe connections with flanges or bits inside the pipe that can whistle when the exhaust passes them. I have also see partially plugged mufflers cause whistles that would seem like an engine issue. a couple of weeks ago I was brought a truck that needed an engine, as diagnosed by a dealership, and found the only issue was a plugged catalytic converter and some tune up issues. not saying that could be your problem, just saying eliminate what you can (good job on removing the belts to eliminate the accy's by the way. good thinking there)
-if you still have a noise you will need to pinpoint if it is engine or trans. you may need to unbolt the torque and slide it back then start the engine and do the stethoscope thing again. if you don't have room between the torque and flex plate you may need to space the engine away from the trans enough to get the job done. if you think it is trans then start by pulling the trans pan off and looking inside. I recommend to drain the pan into a clean container so you can look for metallics in the oil and know that whatever found can only be from the trans (or engine if dumping that oil as well). if you do this and your pan does not have a drain plug then now would be the perfect time to remedy that to make things easier in the future.

keep us posted, post pics and video as you see fit. the one link to a video did not have sound (for me anyway)
what is that behind your trans, overdrive unit? possibly an issue there could make the sound you hear?

Re: What's going wrong inside my 350?
 

sorry for the long boring write up. i's just stuff I thought about that could maybe help you or somebody else reading.

Re: What's going wrong inside my 350?
 

When I say front pump, I mean transmission pump. The pump on the 700R4 has small tabs inserted into a disc that rotatates in an oblong fashion. If the transmission wasn't assembled properly, clearances checked, etc... You can have metal on metal, sqealing etc... If the torque converter wasn't seated properly, and the bellhousing bolted down, you can actually damage the pump, and torque convertor.

You stated that the flex plate wasn't bolted up initially, which is why I'm leaning to the transmission side of things.

Unfortunately, the only way to know is to start pulling things apart.

Chris

Re: What's going wrong inside my 350?
 

Unbolt the torque converter pull it back away from the flexplate and restart it.

I bet the converter wasn't seated properly.

Re: What's going wrong inside my 350?
 

That probably wasn't an issue as he could turn the converter easily to line up the bolts when he put the flex plate to converter bolts in. At least he didn't say it was hard to turn.

Cracked or broken flex plate is usually a rattle or almost a knock that goes away when you put the trans in gear and put a slight load on it. I got a free engine that "had a knock" from one of those back years ago and drove that engine about 80K after that.

You can buy the mechanics stethoscope at O'Reilly's or Autozone for about 8 bucks if you don't have a HF close. The one I use now came from Autozone after one of the ear pieces came missing on my old one. I've done the broom handle thing, hose thing and what not but the stethoscope really works to isolate noises.

It made the noise when the converter wasn't connected so that rather eliminates the trans and converter. To be positive you could pull the three bolts out of the flex plate and slide the converter back in the trans with about a half inch clearance and fire up the engine again. If you already had that clearance before forget that step

You could raise the truck up and have a helper fire it up to see if the starter drive releases from the flexplate when it starts. You would have to remove the cover if you already put it on but that only takes a minute. You should see it pop back as soon as the engine fires up. I'm not sure if you could catch it by laying a phone or camera on video under it and aiming it up there but if you are working alone that might be worth a try. If it is a fresh from the parts house rebuilt starter a lot of rebuiders machine the mounting surface every time they go though the rebuild plant and after two or three go arounds over the years a lot of metal gets shaved off them. It may just need shims.

On old engines with a lot of miles on them I have seen a number of worn out timing chains that rubbed the timing cover with a couple of them wearing though the covers.

Like most other guys on here I am not a fan of Fram filters preferring either the Wix or a Napa Gold. Years ago Fram decided to put most of their money into advertising rather than producing the best filter they could and their filters are far from the best.

Re: What's going wrong inside my 350?
 

DSRaven,

Thank you for all the tips. I read through all your post and I'll update a couple notes.

-I don't believe there is any vac leaks. Carb ports are plugged off. Distributor is plugged off. I also tested removing the PVC and air breather from the valve covers.

-I checked the bolts on the front pulley and harmonic balancer and they are both tight. As far as I can tell there appears to be no wobble in the balancer/pully when the motor is spinning.

-before I installed the distributor I used my oil pump priming tool and turned it over with my cordless drill. plenty of oil was getting up top to the heads and had good oil pressure.

-I don't have a torque convert cover at this time so it's exposed.

-When i noticed the torque converter wasn't bolted up to the flex plate I could spin it with my hand. When I installed the bolts it was easy to slide the torque towards the flex plate. I installed all the bolts by hand easily without having to forcefully pull the torque into the flex plate. Turning the motor over with a 1/2' drive and about one foot wrench was tight but not anymore then i would say normal. I had to turn over the engine to install the distributor to get TDC on cylinder one.

-

Re: What's going wrong inside my 350?
 

the torque converter was missing the bolts to the flex plate.

Re: What's going wrong inside my 350?
 

The sound was there before I bolted the torque convert to the flex plate. Since the truck sat for such a long time I assumed that the torque converter might have rusted itself to the flex plate then finally broke free after starting the truck multiple times.

I figured the sound would have been from the torque converter snout rubbing up against the flex plate but that wasn't the case after bolting them together.

Re: What's going wrong inside my 350?
 

mr48chev,

I appreciate all your input. To answer some of your questions above.

-i wouldnt say the engine was to hard to turn but it took a little arm muscle to get it to move. I was using a 1/2" drive with 1 foot arm on it. Probably would have been easier if I used a longer wrench.

-yes it made the noise before the torque was bolted to the flex plate so that would eliminate the trans and converter. Yes I did have a small clearance before bolting them together.

-I will try to lay my phone down under the truck to get another video. I believe when i checked the starter (engine off), the starter drive(bendix) was back inside the starter.

Could the drive/bendix it get stuck in the out/startup position after starting the engine? then one stopped pull back into the starter?

Re: What's going wrong inside my 350?
 

(Could the drive/bendix it get stuck in the out/startup position after starting the engine? then one stopped pull back into the starter? )
yes

Re: What's going wrong inside my 350?
 

Good to know.

Re: What's going wrong inside my 350?
 

.
.....bingo.!
.

Re: What's going wrong inside my 350?
 

This is not the answer to the problem. The noise was happening before I bolted the converter to the flex plate. I should have an update in the next couple days once I have a chance to look at it closer.

Re: What's going wrong inside my 350?
 

pull that oil filter, cut it apart and have a look see of whats in it and also look behind it (that adapter with the check valve that may be whistling as oil is bypassing). if you find filings in the filter element then you KNOW it's internal and need to stop running the engine since that will cause more damage. that is the quickest and easiest thing to check and causes no more damage if there is an internal issue.
do you have any specs on whats inside the engine? anything different from a stock 350, windage trays, high volume oil pump (which may require a high flow filter) or special timing gear set up etc? have you tried simply swapping the oil filter or listening directly AT the oil filter? some filters have an anti drain back valve built in and this could also be "whistling" as oil goes through it,theoretically. it would be worth a listen maybe. are you sure the oil filter is the correct one for the engine? some filters have the same dimensional size and thread but are made to flow opposite of other filters, so from the inside to the outside or opposite to what a standard 350 would flow. if you have the wrong filter and the filter has an anti drain back valve, then the valve could be fluttering causing the noise or the filter could be bypassing due to low flow through the filter because the filter isn't made to flow the wrong way. you say there was lots of oil flow when you primed the engine but if the system is bypassing it may still have good flow but the oil will not be filtered properly. the bypass is built into the oil filter adapter and is made to open if there is low flow through the filter from cold, thick oil or the filter were to plug up (or you simply have the wrong filter). if a high flow oil pump were used or the builder changed the pressure relief valve setting in the oil pump, then a high flow oil filter may be required. these typically are for race engines where the owners sacrifice filtering for flow.
is there a reason why the engine won't stay running/idling by itself and needs to be babysat? possible cause of the noise as well?
from memory, does the noise increase exactly with engine rpm or stay the same pretty well or only a slight difference with an rpm change? if something were rubbing on a rotating part then it would change exactly as the rpm changes. if the noise is something like, say, a vacuum leak then it would change with rpm but not necessarily be exactly as the rpm changes, if you get my drift?
here is a little video on the oil filter system

https://www.onallcylinders.com/2016/...filter-bypass/

here is a video or 2 showing the filter cut away so you can see the anti drain back valves and what the filters look like inside. some filters have cardboard end caps instead of steel so they would be the lesser quality ones, in my mind.

https://www.youtube.com/watch?v=HXGHA8DUhGQ

https://www.youtube.com/watch?v=X3JulJDNpeU

https://www.youtube.com/watch?v=lrAbxCZlZpE

Re: What's going wrong inside my 350?
 

x2

Re: What's going wrong inside my 350?
 

Lots of good suggestions, but I'm leaning towards the torque converter/flexplate area. I thought the torque converter sure looked wobbly as it was running. I'd also like to see a close up picture of the torque converter bolts on the flexplate. Is the flexplate on backwards?

Also, no mention of transmission fluid in this thing. Does it even go into gear? You could also pull a transmission line and start it up and see if fluid is being pumped. No fluid-no transmission pump.

If it were mine, I'd disconnect the torque converter, rotate and slide it in until it is engaged properly into the pump. Then start the engine while its disconnected from the flexplate and see if the noise is gone. I would want to eliminate the transmission as a problem and then move on to the next thing to eliminate.

Re: What's going wrong inside my 350?
 

dsraven's suggestion to cut the oil filter open has merit. I haven't ever heard a noise that loud from oil flow through a bypass valve but I'll keep an open mind. Thinking back, that noise is vaguely familiar but I can't place it. I have heard a dry rear main seal make noise like that but IIRC that was a one piece rear main, not the two piece you're running now. I suppose a tight set of rings could make a noise and potentially so could a thrust bearing that is too tight fore and aft.

I'm waiting patiently to see how this turns out.

Re: What's going wrong inside my 350?
 

One time a truck that came in the shop with a similar sound. Turned out the owner swapped in a used engine and used the flywheel bolts from a stick flywheel (too long) on his thinner flexplate for the automatic that was in the truck. The too long flywheel bolts were rubbing-hitting the back of oil pan flange on the block. Easy to see with a flashlight from under the truck.....

Steve weim55 Colorado

Re: What's going wrong inside my 350?
 

Like the mechanic at work used to say about noises: "Let it develop." He knew you could spend countless hours tracking down noises, but if you let them alone they eventually made themselves obvious.