PS.....You're video is funny a.f.

I thought it was better but if you run it on the highway for awhile and stop, the pressure drops to around 8psi again. So whatever it is is internal, someone mentioned cam bearings and that might be the deal since I think this was a rebuild and maybe they cheaped out. Was worth a shot though

You may want to replace the oil pressure sending unit. It's located just below your distributor. Turns out that the symptoms you are having are EXACTLY like what happens when that part goes bad . Same thing is happening to mine. Replacing it tomorrow. Will let you know the results.

That was my original hope but I put a mechanical gauge on it before doing the pump and that gauge read about the same. I think the sensor was changed somewhat recently but if not I'll probably get one for it

@@Range-Report do mean when the Gage shares moving up and down all the time

Glad you liked it! I didn't set out for the video to have any kind of comedy (I use that term loosely here) but I really liked how it turned out. And thanks for the tip

That's Sick! Car slogans used to be way better lol. This 350 is still kickin with 7 psi at a hot idle

@@PracticallyStocki know crazy late response but does the low psi cause stalling often?

No worries, on this one it has not. I don't know if low pressure will actually cause one to stall, I have heard that but I've never seen it or known anyone who has actually seen it happen. This truck occasionally has a bad idle hunt, but I am confident that is unrelated.

But oil light is on?

Sounds like that or the gauge may be your issue, can always double check with a mechanical gauge. Best of luck

@@PracticallyStock Thanks! I installed the new OP switch this afternoon and man that was a pain! My OP now holds pretty steady at 25-30lbs. Not as high as I had hoped but I think I'm ok.

Yeah under the distributor was definitely a "good on paper" design, I would consider 25 hot really good. Glad it was an easy fix

@SHAWNTAUR STRENGTH I never noticed a power drop on mine. I did have a similar problem a few years back and I replaced the distributor cap and if fixed it.

your oil pressure is fine.

The issue in this case is the pump is doing all it can but it's not enough for whatever excessive tolerance is in the motor

Took me a minute to realize what you were referring to lol. It came off of a 2000 classic Z71 tahoe as did the rims. These were sold as 2000 models but had the GMT400 body of the 90's. I read they were the left overs from a cop-car deal that fell through but I don't know if that is fact. The car was a really cool metallic dark blue but got rear-ended and totaled so we parted it out

Did you have another gauge to verify the dash was correct? Odds are it is right, but ya never know. 329K is a lot though, I've been surprising by the number of tbi and vortecs over 300K I've seen

​No, but the oil filter definitely told me it was accurate. With the low pressure, i was getting excessive metal in the filter and on the magnet. After bumping it up, i haven't had a speck of metal anywhere. Doesn't knock or anything. Still running strong ​@@PracticallyStock

Not really, whatever is wrong with it is internal. Since it didn't even have 30K miles on it, I was worried the problem was something more serious but the pump was worth a shot. Going to run it until the issue is clear enough to pin point

Damn that’s a bummer! I’m still on the fence about changing mine. Good luck man

@@Drater87did you end up doing this? Mine has the same issue. ‘94 just rolled to 170k

Jesuscordova I didn’t do it, I just saved up to get a crate motor. Now im saving to get it installed.

I don't know who made them. They came factory on 2000 Z71 Tahoe classics. Those Tahoes were sold in 2000 but they were the old body style. They came with the grill guard, special rims (also on the truck), different tail lights and special running boards. I have never seen one come up for sale nor have I been able to find one, I have such a Tahoe but it is missing the grill guard which sucks

Sorry to hear that, it was a huge pain to do and the cheap oil line fittings went to leaking right after I got it back together. Maybe double check it with another gauge to make sure the dash is right, best of luck

THE PRESSURE RUNS 10 PSI FOR EVERY 1000 RPMS.. if your idleing at 800 rpms, 8 psi is ok, standard transmission trucks idle a little higher, 850 to 875. in closed loop.

@@randy1ization same as my 91 5.7 its been that way since birth its the flow that counts not the pressure , if your lifters Arnt rattling we don't worry about it , that engine sounded quiet to me .

@@randy1ization those engines love 10/30

@@oldbiker9739 I run a bottle of marvel mystery oil in the tank every other fill up, and it keeps my valves and lifters clean and smooth,, I found out what is in MMV,.. sent some to a lab.. the active ingredient is WHITE PHOSPHEROUS., it burns hot.. used to be used in the millitary, they called it Willy P. they dropped it on buildings and it will burn thru metal... something gas used to have plenty of it in, but due to EPA, it doesnt contain much anymore.. I borescope my valves now and then and they are very clean. with the 205,000 on the clock, she was a little sluggish, so I advanced the timing a couple degrees, polished the throats on my throttle body and rebuilt it, and it runs like a scared rabbit now,, very torquey and responsive. also a new distributor made a huge difference because they wear at the gear and spacers, and get sloppy.. also the star magnet in the distributor gets weak from the constant engine heat,, its slow and over time u dont notice it much, but when u replace the distributor its like night and day. also couple that with worn timing set, and your static timing is usually off even though your timing light says good.

Glad to hear it! The latest video of the S10 isn't as entertaining but it's a similar style

It's not as high as I would like but it's safe and better than what it was. So far it's been staying off the red and closer to 15psi

I haven't heard of that happening, seems like it would be a liability issue to design it that way

@@PracticallyStock thank you

Hard to say. Whatever it is, there are no other symptoms or noises and it doesn't seem to be getting worse

The problem for me was 1) something changed in the motor to cause low oil pressure and I wanted to know if I needed to start putting another short block together. 2) The oil pressure was good enough to not trip the light but I don't like running equipment at the extremes of its allowable range especially since this is a fairly new engine. I don't think the bypass would be affected, the bypass for the filter should only trip if there is a large differential across the filter, if it's the bypass in the pump that trips then that doesn't get filtered but I think it just goes back to the pan

@@PracticallyStock I think it goes to the mains. the spring in the bypass is not very strong. if the oil went back into the pan the system would be pointless.

@oracle wisdom I did some looking and the filter bypass just bypasses the filter and assuming the filter never clogs, should never have to do anything. There does seem to be a bypass in most oil pumps and it bypasses excess pressurized oil back to the pan once the pressure reaches the spring's setpoint. Since the bearings are where the resistance to flow is, the oil has to be bled off before them, similar to how a fuel pressure regulator bypasses gas back to the tank when pressure is adequate. Once the oil warms up and can flow through the bearings with less resistance the bypass will close and reopen if rpm brings pressure up past the setpoint

@@PracticallyStock do some research on the crappy oil filters being sold,, there are several on you tube,, rusty inside, metal shavings loose filter material, ect,, all I will use is WIX.. something could have come loose in the filter and stuck in the byspass valve keeping it open,, I started filling my oil filters with a little new oil sloshing it around and dumping it,, the chinese dont give a rats ass about your engine, its either that or your bypass spring has gotten weak, and is bleeding by . jmho.

Fram filters are the worst you can buy, !!!! followed by STP... I will use WIX or ac delco brand only,., have 202.000 on my 94 sliverado and it runs like new,. I run a half bottle of marvel mystery oil thru the gas every 3rd tank ful of gas, and dump a 1/2 bottle in the clean my engine abt 20 miles before an oil change. I use valvoline conventional motor oil or mobil 1. my truck is a workhorse and tows a heavy boat on most trips, usually around 50 miles both ways. I recently replaced the valve stem seals due to age,, I plan to go another 100,000 before rebuild, I have a 93 k2500 with 425.000 before the head gasket blew. I found out why head gaskets blow,,, coolant passages in the block clog up over time,, just because your coolant is still green doesnt mean its good,, the antifreeze has lubricants in it that wear out. do a VERY THOUROUGH BLOCK FLUSH .. I recently did my 94 and had to do it 3 times to get it clean,, the heater cores hold alot of rust for some reason. also make sure you have a 190 t stat in your engine, running too cold causes problems,, I know these trucks very well.,,. its what I drive by choice.. I can drive anything I choose, but love the gmt 400s, especially 88 to 94.... 95 was a hybrid of sorts.. I avoid them.. you have a great truck, treat it great and it will last... change your rotor at least once a year, and if your distributor has alot of miles replace it,, the shaft bushings wear, the magnetic star wheels lose thier magnetism over time, ect.. put a new AC DELCO distributor in it,,, now for fuel pressure,., there a spring in the throttle body that can rust, weaken and break,, I rebiuld and polish the throats of the throttle bodies,, make a great responsive difference, more power.., DO NOT PUT A HIGHER TENSION SPRING in the throttle body.,, these trucks like 9 to 13 psi of fuel pressure,., I high tension spring will cause a miss on the top end with no increase of performance on the low end.. change your fuel filter in the frame rail if you havent done it.,., get you a set of high performance plug wires, the 20.00 set at autozone is shit.. I use belkin blue wires.. worth ever penny,., make sure your coolant temp sensor is clean where it goes into the block,,, the ground wires that go to the top of the thermostat lugs, clean them and put liquid electrical tape on top so they dont corrode.., and last but not least, if your main battery ground wire goes to to aluminum accessory bracket on the front of the engine, relocate it DIRECTLY TO THE BLOCK,, use a large diameter solid copper ground wire,, biggest you can find.. and where the positive battery wire runs along the frame to the starter, make sure it is well insulated, and in its insulated retainer so it doesnt chafe and ground to the frame rails. if your going to keep the truck, buy you an OBD1 compatible scanner,, you can do alot with it,, mine is an autel.. I can check everything out, fuel trims, coolant temp, egr functions, ect. I keep my truck in stoiciometric effiency. IT RUNS LIKE NEW.! If you have a question abt these trucks, dont hesitate to ask,, theres also a group called GMT400 that has a mecca of info regarding these trucks,, im a member.., {TEXAS TOUGH).

That's good info to know. I don't think that is the issue in this case because the 68 gmc has the same universal hose and I would expect both to have the same problem if that hose material was collapsing. I wondered about a restriction in the cooler (new rad) but it was fine the first 20ish thousand miles and I figure if the cooler got clogged in 20k then something catastrophic happened like a oil filter element coming apart and the motor would probably need pulled anyways. The adapter has leaked several times so I know it's clean lol. I personally really like coolers, the engineer in me just loves them. Since the oil cools the pistons and bearings I like the oil to run around 170-180F in the gmc no idea what the silverado runs unfortunately. Clearly a oil cooler isn't required but I believe it lessens the strain on the oil and keeps it from breaking down as quick, helping the motor as a whole. Did you ever find out what exactly stopped yours up?

@@PracticallyStock no I don't know what exactly clogged up the lines but regardless if they're clogged up or leaking they can cause low oil pressures.

@@PracticallyStock plus my temperature stayed the same when I deleted the oil cooler lines but it did give me better oil pressure at idle and driving when I deleted it

@@PracticallyStock I also toad heavy stuff without the oil cooler being on my truck an I had no problem with it overheating or the oil being thinned out.

Definitely pros and cons to it

Kinda where this one is at, but I bet it still has a long life the way it is

The difference was negligible. The low pressure is something internal to the motor

If you have an old body style S10 I have a similar one. Generally speaking, once the oil is at operating temp, pressure will change with engine rpm. The pump on a 4.3 is driven by the cam so the volume of oil it pumps changes with engine speed. Higher rpm = more oil flow. The lowest pressure will be at idle since that is the lowest speed and thus pumping rate. As rpm increases, flow also increases which causes an increase in pressure as the additional oil has to force its way through the engine. An oil pump has a bypass that will bypass oil flow back to the pan once a high pressure is achieved. You often see this on a cold start when at idle the pressure goes around 60+psi because the oil is thick and resist flow. Every engine has a slightly different rule but there is a minimum pressure at idle and an expected increase in pressure for every 1000 rpm. The 4.3 in my s10 (at operating temp) is about 15-20psi at idle and 40-45psi at 2400rpm. If the pressure is drastically changing but rpm is not, then that may be a problem. If pressure rises and falls with rpm, it's probably good unless there is something else you are seeing to suggest otherwise. I just do this as a hobby, but hopefully that was helpful

Yes but as stated, the oil pump can have excessive clearance as well and I would argue this can have the worst effect on oil pressure. The pump was the easiest thing to change and made the most sense since this motor had good oil pressure when new, did not have many miles on it, has been well maintained, and did not have debris in the oil filter that suggested a bearing failure. Even on a more worn out motor I would still potentially do this since in my mind the oil pump should wear out first since it does not get filtered oil, but a rebuild would be in the future regardless

@@PracticallyStock It don't matter, the gauge only measures the pressure going through the crankshaft. The chain is flung by a disk, topside is flooded and runs down the valley and also wicked around below the camshaft. Low oil pressure means open crankshaft tolerances and easy flow.

@@NicholasMaietta If you've got the pump out, you can change the bearings too before closing, in fact the oil pump is attached to a bearing cap housing. To change crankshaft or arm bearings, remove oil pan and begin. Engine still in car. Oh, remove spark plugs to make hand cranking it easier, much easier. And, slightly tap back on the harmonic balancer so you can just reach up and hand crank from under it.

@Odd Ball I want the oil pressure to run well in its tolerance, easy flow doesn't necessarily mean strong film strength

I think you're right in that the bypass is likely the problem. I don't think the issue is outside the oil pump because I set the new pump up exactly like the old one and the problem seems to have gone away. I went ahead and welded the pickup tube since I had the pump out

@@PracticallyStock with a new, high flow pump, your pressure may have increased but the question is, is the oil going thru the filter, or the bypass. stuck valve or weak spring would let the oil go past the filter... if you take the filter off and look in there, theres a pressed in valve, with a little plastic cover that sits atop a little spring,.,. you have to kind of pry on the little lips on the side to get a place to pull it out,, its not pressed in very hard. I would pry it out, install a new one and see how it does.. on these old trucks the rule of thumb is 10PSI FOR EVERY 1000 RPM. So if your idling at 800 to 850 rpm, 8 to 10 psi is acceptable.. I know it sounds low, but they work. pressure and volume are 2 VERY different animals. high oil pressure can actually create less flow due to differing sizes of orifices thruout the oiling system. if you put 50 psi of pressure on a small opening, it will come out with more VELOCITY, but not more volume. you garden water hose is an example of this.,., you run your faucet thru a small hose and it shoots the water further than a larger diameter hose. so you think, man its really flowing now,, ha

@@PracticallyStock now the 96 and up chevy small blocks, they run higher pressures. this is where the 'UPGRADE " high volume pump came from, but Its up for debate if this is really an upgrade or a potiential problem maker. if the higher pressure bottlenecks the FLOW, its going to starve certain paths of the engine of oil. likely the upper valve train. engineers figured all of this out several decades ago.., you have to really think abt so called upgrades that everybody thinks is the answer. on the 89 sbc 350 I built we put a high VOLUME pump on it, not a high pressure pump. I think it may have an extra pump vein or 2 in it, but is not engineered to spin the shaft faster..

Sorry lost track of this comment chain. I apologize I went back and looked and I believe I installed a M55 which should be a generic SBC pump and the M155 that came out of it was the LT1 pump. When the motor was first installed it made the same cold oil pressure the 305 did 40-45psi so I don't really think there was anything special about it regarding flow and pressure. Thanks again for the info

warning though I found out welding the pick up to the pump can heat up and damage the by pass spring.

(keep in mind I'm just some guy on the internet) I would go through the same process I did. I wasn't too worried about this motor since the low oil light never came on but I would first Verify low oil pressure with a good gauge. From there it's hard to say not knowing the condition of the motor or other factors. If the motor has had a rough life (extended oil intervals) then a pump may help but not make it normal because a pump can't fix worn bearings. If it is idling really low then that may also be contributing but I think that would be pretty obvious. I don't want to give you an opinion for fear of steering you the wrong way, but if the oil pump had made no difference in my truck I was going to run a thicker weight oil like a 5w-40 and start getting another short block built. I would run the truck motor till it started having real problems then pull it and clean/swap its heads onto the new short block and put it back in the truck. That might not be best plan for you but that was what my idea was

@@PracticallyStock thank you. yea I'm not sure. I'm not a mechanic but it was my every day driver until the engine started to stutter. the truck would feel like it was going to die when I came to a stop. then noticed oil pressure was dropping to about 5 on my oil pressure gauge but while driving it did fine

@@Jay-zx8fj Yeah maybe fix the running issue and reassess it, if TBI you can always check for big vacuum leaks especially with the line running to the MAP sensor. Fixing idle issues on the TBI systems seems to be a pain, my truck has had a random stumble in it for about a year and without throwing parts at it I don't know what else to do so I figured I would just wait till it got bad enough to properly diagnose. If you can hold it at a idle with your foot and it has decent oil pressure I would think the motor is fine, best of luck

I have a 92, 4.3 tbi, 15psi when warm. It always had a knoching noise, the engine was rebuilt and the same knocking noise. The mechanic did not change the oil pump, so i wonder if the problem has ever been low oil presure.

@@isaacsanchez8203 (Keep in mind I am no professional) Hard to say, 15psi seems fine to me but it's weird someone would rebuild a motor but not throw in a new pump. Low oil pressure won't cause a knocking noise but could be a symptom of excessive bearing tolerances which would cause knocking. Maybe it needed the crank machined and undersized bearings. If it only knocks on start up then I would guess it's the bottom end or a lifter bleeding down but not crisis yet. You can take a metal rod like a long socket extension and put it to your ear and touch the other end to the motor and listen. Can get a idea of where exactly it's coming from. Have a video of a 300z called "Fixing a knocking noise" where I did this and found the noise was the catalytic converter

So far it's been better than than it was. I have not seen it on the top of the red again but it's still only about half way between that and 15psi

That would be a judgement call and quite subjective. Granted I don't have a ton of experience, but if the oil or filter had only some specs of metal I probably would have left it and just kept an eye on it after doing the pump, probably set aside some cash to fix it if needed. However, if the oil/filter had a considerable amount of metal and bearing material in it I would have stopped where I was at and started sourcing a good short block for it. That way I could swap the heads to the new short block and then either rebuild or scrap the bad one. Or maybe just put the 380K mile 305 back in it lol

Get ready for a motor rebuild or replacement.

Thanks! I unfortunately didn't notice any difference with the new pump. The problem is internal to the motor

Thanks for reply I was afraid of that being the case

@@vincentmayer8511 No problem, it could still help depending on the situation. The 305 that used to be in this truck had low pressure because the pickup screen was gunked up with rtv. A new pump fixed the issue in that case. I would check it against another gauge before worrying too much

Yes sir I put mechanical gauge in and reading same as dash Gonna pull pump and see again thanks for video is a big help

If it's not coincidence maybe the oil had too many miles on it or was diluted with gas?

@@PracticallyStock she was burning oil over time. No biggy

1992

I imagine they all have their BS designs lol

Fix Or Repair Daily

I tell u what!!!

I try to limit my exposure lol

I think high idle can be several things. Bad IAC, vacuum leak, sticky throttle maybe? If the engine won't stay at temp I think it would likely be the thermostat. For the engine to not build temp the only cause I can come up with is coolant is making it past the thermostat and through the radiator even when it shouldn't. I am having this problem with the blazer and in my case (since the thermostat is new and I tested it in a hot pot of water) I think the thermostat is fitting real loose in the housing and coolant is flowing right around it, but I have not verified this

​@@PracticallyStock no it goes down when warmed up it just gets cold fast i live in bc canada so my weather is on and off as in the coldness

its probably not going into closed loop,., coolant temp sensor on top front of engine, or oxygen sensor bad. is it blowing black smoke?

@@randy1ization i fixed it it was the carn and intake thats all hahah

@@robertpeters1497 where is the CARN located,.,. hahahahaha

I think the absolute minimum is 4-5psi or something like that. I'd be plenty happy with 15psi

There are a few places but I removed the plug shown at 1:43 and used that port. Have to make sure the line won't touch the exhaust though

Thanks! By the way in my case, I clean cyl heads, lifters and oil pan; replace sending unit and oil pump, just for preventive. Oil 10w30 as usually and my pressure drops like yours 😅 8 psi warm and idle. Adding a oil additive increase to 10psi. But not noisy lifters so I think it’s ok 🤷🏽‍♂️

@@LaloNavarroII That's where I am at with this one, I figure if it is unhappy it will let me know lol

I will at some point before I get rid of it. The 305 had a pump get weak and replacing it fixed it till the motor was pulled (still healthy) at 381K. Yes it's the most lubricated but I would argue that ideally it should be the first part (at least that is pressure lubed) to wear out since everything else gets filtered (and in this case cooled) oil and the pump does not. I would not be surprised it there was still an internal issue in the motor but as of now replacing the pump has correct the oil pressure

The dash gauge was accurate and verified by the mechanical gauge. I didn't want a high volume pump because if the pump was the problem then a high volume pump would add unnecessary strain to the timing chain and distributor gear. I also don't want to mask the problem with more oil flow, I would rather pull the motor and fix it if the issue worsens

Well if you pull the pan you could look for debris/sludge. This motor is a GM rebuild but it has to have an internal leak somewhere causing the low pressure. The original motor got low pressure from the pick up screen being clogged with RTV scraps. Maybe check under a valve cover and see how sludgy it looks? I can say it could be worse, I recently spent 4 days on my 4x4 S10 fixing a stripped drain plug, I would have rather done this job twice lol. If a fresh motor makes the most sense for what you need the truck for then that may be the way to go. (Check it with a good gauge if you didn't already to make sure it actually has a problem) but if you do the pump and it doesn't work, at worst you've likely just lost a weekend. Hopefully something in this rambling was helpful, best of Luck in your endeavor

I ragged on them pretty good but in there defense it's probably more a management problem not allowing for further refinement

I didn't since it was working correctly. With the quality of parts these days, I don't like replacing stuff that isn't broke

@@PracticallyStock totaly agree with you on that , reason i asked is because i replced it on my pick up , my pressure was reading basically nothing and now its at id say 8-10 psi, and im tempted to change the oil pump as well to see if it helps a bit more

I see, I was worried about that as well so before doing the pump I hooked up a mechanical gauge which unfortunately verified the truck's gauge was working. This one is still doing fine with its 8psi at a hot idle

Or it could be literally any other bearing, crack, or plug exposed to an oil passage for the same reason that it could be cam bearings. It could be cam bearings but I don't see how any other internal leak can be ruled out

Problem is new trucks are so expensive it makes sense (at least for me) to put some money in one of these and keep it

EDIT: My bad I thought this was the other truck we messed with, this one had no sludge in the pan. It has only about 20k miles on it

Could you elaborate? I am not sure what you are referring to

Call it whatever you like, it's way better than it was and was the easiest potential problem beyond the gauge

Thanks! The gross amount of sarcasm made working on it a little more fun lol