PauliusB Posted January 31 Share Posted January 31 (edited) Hi, I'm concerned about my Riviera's hot idle oil pressure and was wondering if it's too low to be drivable. Oil pump is replaced to a new stock one, when I start it up, pressure is at 40 psi, however as the engine comes to temperature it drops to 6-7 psi. I know Buicks with external oil pumps tend to have low oil pressure, but I would expect it to be at least 10 psi. If I rev, pressure goes up sufficiently. My questions are: 1. Is this too low (6-7 psi)? If yes, should I verify another probable cause, which is bearing clearances? 2. Also, inside valve covers it is completely dry, I've never seen this on other cars, is this normal again? I would expect oil to come through the lifters. Thank you! Edited February 1 by PauliusB (see edit history) Link to comment Share on other sites More sharing options...
EmTee Posted February 1 Share Posted February 1 Found this: https://www.greatautohelp.com/operation/3800-oil-system.html "Oil is drawn into the pump through the screen and pipe assembly, and a passage in the crankcase, connecting to the passages in the engine front cover. Oil is discharged from the oil pump to the oil filter adapter. The oil filter adapter consists of an oil filter bypass valve and a nipple for installation of an oil filter. The spring-loaded oil pressure relief valve, located in the engine front cover, limits the oil pressure. The oil filter bypass valve opens when the oil filter is restricted to approximately 68.95 kPa (10 psi) of pressure difference between the oil filter inlet and discharge. " I would check the bypass valve in the oil filter adapter, then the pressure relief valve in the front (timing) cover. I'll bet something is going on with the relief valve... 1 Link to comment Share on other sites More sharing options...
PauliusB Posted February 2 Author Share Posted February 2 Thank you for your answer. But would you say my idle pressure is actually too low? On 2/1/2024 at 2:29 AM, EmTee said: Found this: https://www.greatautohelp.com/operation/3800-oil-system.html "Oil is drawn into the pump through the screen and pipe assembly, and a passage in the crankcase, connecting to the passages in the engine front cover. Oil is discharged from the oil pump to the oil filter adapter. The oil filter adapter consists of an oil filter bypass valve and a nipple for installation of an oil filter. The spring-loaded oil pressure relief valve, located in the engine front cover, limits the oil pressure. The oil filter bypass valve opens when the oil filter is restricted to approximately 68.95 kPa (10 psi) of pressure difference between the oil filter inlet and discharge. " I would check the bypass valve in the oil filter adapter, then the pressure relief valve in the front (timing) cover. I'll bet something is going on with the relief valve... Link to comment Share on other sites More sharing options...
EmTee Posted February 2 Share Posted February 2 If the hot idle oil pressure is truly 6 ~ 7 psi, then I do think that's unusually low for a 3800. First thing might be to temporarily install a mechanical oil pressure gauge and verify the readings. Second, make sure the hot idle speed is correct. Offhand, I'd expect hot idle in Drive to be ~650 RPM. Link to comment Share on other sites More sharing options...
NTX5467 Posted February 2 Share Posted February 2 Just curious which oil viscosity is being used? How many miles on the engine? Does the engine make any bearing-related noises when starting from sitting overnight or after sitting from not running when hot? In the short run, as long as the oil pressure is to spec at 1000rpm or whatever, lower pressure at hot idle should not be an issue. On one hand, the old "rule" for oil pressure for HP work, using the higher rpms to determine pressure at those rpms, it was "10psi/1000rpm". Using that to work backwards, a 700rpm idle would be 7psi. Don't know if it works like that, though. In a 1950 Plymouth service manual, it mentions that ANY oil pressure at idle is fine, even if its 1psi I guess? Different ways to look at it! For reference, my 2005 LeSabre Series II 3800 shows about 37psi at hot base idle. You can remove the engine and check the crankshaft bearings at some time in the future, if desired. If the engine has never been into, might be something to work toward? But as long as the engine is "quiet", might not be an issue. NTX5467 Link to comment Share on other sites More sharing options...
60FlatTop Posted February 2 Share Posted February 2 I remember a time in the 1970s when cars were experiencing their oil lamp flickering at idle when the cars were at operating temperatures, especially at stoplights. Back then the word I got was that there were lower pressure rated oil pressure switches available since the cars were dropping to that 4-5 PSI range.. I am not a big fan of add on gauges except for testing.Gauges tend to be less reliable than the systems they monitor. Link to comment Share on other sites More sharing options...
PauliusB Posted February 11 Author Share Posted February 11 On 2/2/2024 at 6:19 PM, NTX5467 said: Just curious which oil viscosity is being used? How many miles on the engine? Does the engine make any bearing-related noises when starting from sitting overnight or after sitting from not running when hot? In the short run, as long as the oil pressure is to spec at 1000rpm or whatever, lower pressure at hot idle should not be an issue. On one hand, the old "rule" for oil pressure for HP work, using the higher rpms to determine pressure at those rpms, it was "10psi/1000rpm". Using that to work backwards, a 700rpm idle would be 7psi. Don't know if it works like that, though. In a 1950 Plymouth service manual, it mentions that ANY oil pressure at idle is fine, even if its 1psi I guess? Different ways to look at it! For reference, my 2005 LeSabre Series II 3800 shows about 37psi at hot base idle. You can remove the engine and check the crankshaft bearings at some time in the future, if desired. If the engine has never been into, might be something to work toward? But as long as the engine is "quiet", might not be an issue. NTX5467 I'm using 10w30, engine's got 68000miles. When I bought it, it had a blown head gasket and a deformed head, which might indicate overheating in the past, but it's all sorted now. So just wondering if bearings (or someting else? )could have taken a toll because of that? When starting cold, there aren't any weird noises whatsoever. Also I'm using a mechanical gauge to verify the readings. I am planning to drop the oil pan tomorrow and inspect crankshaft bearings. I'm also thinking about camshaft bearings if they should be inspected, but the work required to take those out would be much bigger, so I'd like to leave this as a last resort. Would this also be worth considering you think? As far as I know, crankshaft bearings is a more potential cause for low oil pressure rather than camshaft ones. Link to comment Share on other sites More sharing options...
NTX5467 Posted February 11 Share Posted February 11 Not sure about the cam bearing side of things. When you drop the pan to check the bottom end, you can also check for accumulation in the pan AND how clean the oil pickup tube screen might be. There is a gasket between the pickup tube and the block, if you want to remove it for cleaning. Head down to an auto supply and get a strip of PlastiGage to check the bearing clearances with. Plus a can of brake cleaner to remove oil from the bearings being checked. Just remember to re-oil the bearings when you put them back together. Please keep us posted on what you find. NTX5467 1 Link to comment Share on other sites More sharing options...
PauliusB Posted March 18 Author Share Posted March 18 (edited) On 2/11/2024 at 5:33 PM, NTX5467 said: Not sure about the cam bearing side of things. When you drop the pan to check the bottom end, you can also check for accumulation in the pan AND how clean the oil pickup tube screen might be. There is a gasket between the pickup tube and the block, if you want to remove it for cleaning. Head down to an auto supply and get a strip of PlastiGage to check the bearing clearances with. Plus a can of brake cleaner to remove oil from the bearings being checked. Just remember to re-oil the bearings when you put them back together. Please keep us posted on what you find. NTX5467 Oil pickup tube looks like brand new. Pulled the main bearings and saw that number 2 (is it a thrust bearing?) is pretty rough as well as on crankshaft side. I can feel the grooves with my finger nail on the crank. Others look pretty good. I'll be getting the crank to the machine shop soon to check if it's fixable Would you think this might be the cause? Would could have caused this only for this bearing? Edited March 18 by PauliusB (see edit history) Link to comment Share on other sites More sharing options...
NTX5467 Posted March 18 Share Posted March 18 Thanks for the update. The crank will probably make a .010/.010 undersize on that one journal. Might probably do the rest of them, too. Used to, many machine shops kept a Buick 3.8L 10-10 crank kit in stock for this situation. When you get things back together, in the new oil, add a "cleaner" additive to thie new oil. It was common for the center main to have issues after about 70K miles, back then. Seems that when they machined the as-cast main oil galley, Buick used two shorter drill bits, one from the front and one from the rear, to finish-size the galleys. They did NOT touch in the middle, so the middle main's part of the galley did not get the same volume of oil as the other mains. In one respect, one main needs less oil that more do, but that's a good theory. The old Buick Performance hand book said the FIRST thing to do to a Buick V-6 block is drill the main galley all the way through, with a LONG drill bit (as other brands use). In any event, modern oils are better than the older ones, generally. It'll be fine when it's all back together. Just some thoughts and observations, NTX5467 1 Link to comment Share on other sites More sharing options...
PauliusB Posted March 22 Author Share Posted March 22 (edited) On 3/18/2024 at 10:01 PM, NTX5467 said: Thanks for the update. The crank will probably make a .010/.010 undersize on that one journal. Might probably do the rest of them, too. Used to, many machine shops kept a Buick 3.8L 10-10 crank kit in stock for this situation. When you get things back together, in the new oil, add a "cleaner" additive to thie new oil. It was common for the center main to have issues after about 70K miles, back then. Seems that when they machined the as-cast main oil galley, Buick used two shorter drill bits, one from the front and one from the rear, to finish-size the galleys. They did NOT touch in the middle, so the middle main's part of the galley did not get the same volume of oil as the other mains. In one respect, one main needs less oil that more do, but that's a good theory. The old Buick Performance hand book said the FIRST thing to do to a Buick V-6 block is drill the main galley all the way through, with a LONG drill bit (as other brands use). In any event, modern oils are better than the older ones, generally. It'll be fine when it's all back together. Just some thoughts and observations, NTX5467 Thank you for your insights! Apparently, the crank is done... It had already been resurfaced to 0.020" by previous owners and they wore it beyond 0.040" limit (on 2 journals) according to the machine shop. Any recommendations on what to do next? I've heard there is an option to resurface a crankshaft in some shops, where they add a new layer to the journals so that they are back to factory parameters. Is it a reliable option or the crank might become more fragile after that? Another option is of course to buy a new one, but so far it's been pretty tricky to find one. I can only find performance cranks with 3.625" stroke, whereas stock is 3.400". Just a random thought, would a crankshaft from 3800 fit my 231? Starting to become really frustrating.. Edited March 22 by PauliusB (see edit history) Link to comment Share on other sites More sharing options...
EmTee Posted March 22 Share Posted March 22 Maybe consider a good used engine? Or, if the rest of the car is in nice shape I'd look into a remanufactured long block. https://www.jasperengines.com/ 1 Link to comment Share on other sites More sharing options...
NTX5467 Posted March 23 Share Posted March 23 The 3800 should be an "even-fire" with off-set rod journals. The 231 has normal rod journals. It is possible to rebuild the journals by welding new material onto them, then machining them to the desired size. I don't know how expensive it might be to do that, compared to what a new GM crank might cost. OR a reman engine, for that matter. One thing I've noticed about Jasper kits is that they come with everything you'd need to change the motor. Belts, hoses, and such. WITH a higher pricetag, too. They also have a chain of approved shops to do the engine changes, too, which gives them the confidence to have the warranty coverage they do. I did a Google search and came up with a good many possibilities. A few crankshaft "kits" (re-ground stock cranks with new matching size bearings) for about $350.00 + 150.00 core charge. Close to the price of a new SCAT stroker crank. You need a cranks with the same stroke as you now have. The interesting item was a new GM Crank on Amazon for less than $200.00. Of course, you'll need to get new bearings with that one, but it had a current GM part number so it might be that your machine shop operative could get that one and bearings for a good price. Knowing these things, the question is "What kind of condition is the rest of the motor in? How many miles and such?" IF you plan on keeping the car for 5+ years, it might be best to find a quality reman motor and fix a lot of other things in the process, too. You can probably find a nearby Jasper installer shop near you via their website. Then contact them to see what the turn-key price would be, plus any additional price for the worn crankshaft. I would advise against a salvage yard motor as anything you find there, for your model year, can very well be in worse shape than the one you have now. Plus it will probably have been "sitting there" for years, which can cause issues because of that, too. Which means anything you might buy will be as a "buildable core", but given the track record of those engines, you would be spending money for another engine that needs to be rebuilt, at best. Do the Google search for "Buick 1980 231 V-6 Crankshaft" and see what comes up. If that GM Parts crank is what it's supposed to be, that would be the best choice and put some OEM quality bearings with it in the correct size (which means verify the size of the journals before getting the bearings). Then a reman crank from a quality crank grinder company with the bearings, buying it out-right with no core. Or a new crank of the correct stroke via Summit Racing (which was one of the items from the search). eBay vendors? I respectfully advise to not go there as you never really know what you will be getting, sometimes. Use that as a last resort of sorts. Hope this might help, NTX5467 1 Link to comment Share on other sites More sharing options...
Aaron65 Posted March 23 Share Posted March 23 6 hours ago, NTX5467 said: The 3800 should be an "even-fire" with off-set rod journals. The 231 has normal rod journals. Didn't the 231 change to even fire around '78? Link to comment Share on other sites More sharing options...
gungeey Posted March 23 Share Posted March 23 17 hours ago, PauliusB said: Thank you for your insights! Apparently, the crank is done... It had already been resurfaced to 0.020" by previous owners and they wore it beyond 0.040" limit (on 2 journals) according to the machine shop. Any recommendations on what to do next? I've heard there is an option to resurface a crankshaft in some shops, where they add a new layer to the journals so that they are back to factory parameters. Is it a reliable option or the crank might become more fragile after that? Another option is of course to buy a new one, but so far it's been pretty tricky to find one. I can only find performance cranks with 3.625" stroke, whereas stock is 3.400". Just a random thought, would a crankshaft from 3800 fit my 231? Starting to become really frustrating.. I find it odd your machine shop measures 2 bearings with a gaping 020 wear yet the other 2 are in or close to spec while you're getting 7lbs of pressure at hot idle. If you get a replacement crank your rotating assembly would need to be balanced. That's a complete teardown. A lot of cleaning, inspection for further damage and wear... and it goes on. It really depends on your long term plans for the car, I think the most cost effective solution is a salvage yard engine 1 Link to comment Share on other sites More sharing options...
EmTee Posted March 23 Share Posted March 23 16 minutes ago, gungeey said: It really depends on your long term plans for the car... As I also noted above. So, what kind of shape is the car in? How many miles? A couple of pictures would help... 1 Link to comment Share on other sites More sharing options...
PauliusB Posted March 23 Author Share Posted March 23 (edited) Thank you all for your responses. The problem is I'm located in EU and finding a new engine of course would be the best choice, but it's impossible to find something within driving distance. I have to ship everything from US and shipping costs increase exponentially as part size or weight gets larger, shipping a crank alone puts an extra 500$, so I'm trying to save the current one, but of course if necessary I'll ship one here. Shipping an engine - that's too much, so that's off the table. As for the car, the plan is to prepare it for summer driving for indefinite time (as long as nothing critical happens). When I bought it, it had 68k miles, engine disassembled and stored in the trunk of the car, nice interior/exterior, no rust. It apparently had a blown head gasket, head was deformed and car itself hasn't been run since 2012. So the process went like this: heads were machined to an even surface, head gasket replaced, block inspected for cracks (all good, so I'd assume it's possible to rebuild), oil pump replaced, filter, oil. Compression was good in all cylinders, was able to start it up and idle. Transmission works. Noticed that valve covers / rocker arms are completely dry and idle pressure at hot idle drops to 7-5psi, but what's worse is that carb/timing is not tuned yet properly, so my idle is probably at ±1000rpm, maybe even more (you might hear it in the video below). And that's where I decided to take the crank off and saw what I saw. I'm more limited to possibilities, since I'm unfortunately not from US, but the plan is stick around with this car and try to do what's possible - I really like it. On Tuesday, I'm taking the crank to another machine shop, which does rebuilds and will see what they'll say. As requested, here are some photos and a video of a running engine (don't mind the pressure reading, it's only after ±2 minutes) - https://streamable.com/10iidl I hope I answered your questions. Edited March 23 by PauliusB (see edit history) 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted March 23 Share Posted March 23 In 2011 I looked at lots of options for my badly abused sludge encrusted, non-running 1986 Park Avenue. I located a long block at an engine distribution warehouse in St. Petersburg, Fl. for some like $300. Some of that stuff gets dusty as the model years age. And they are happy to move it out. The engine had been rebuilt by one of the large southern rebuild houses. I don't recall the name of the rebuilder or distributor but a little investigation may exceed your expectations. Terminal to terminal freight is quite reasonable. In a similar vein, I am going to need a right side CARB catalytic converter for my '05 Cadillac STS V8. How many buyers are there for those manifold integrated dust collectors. Oops! I was just ready to push the submit button and your location popped up. Maybe someone else can use my tips. 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted March 23 Share Posted March 23 18 minutes ago, PauliusB said: The problem is I'm located in EU If you want a real treat slide behind the wheel of a Bentley T-series. You will be shaking your head going "How'd they get away with this?" Link to comment Share on other sites More sharing options...
EmTee Posted March 23 Share Posted March 23 20 minutes ago, PauliusB said: The problem is I'm located in EU... OK, thanks for that important piece of information. The car certainly appears to deserve the effort required to get it running again. Given your location, perhaps a new crankshaft and rebuild of the original block makes the most sense; particularly given that the top-end has already been done. 1 Link to comment Share on other sites More sharing options...
EmTee Posted March 23 Share Posted March 23 Assuming that you decide to remove and rebuild the engine, I suggest that you also inspect the condition of the transmission. At least remove the pan and evaluate the amount of sludge accumulation (i.e., cast-off clutch material). At 68K miles, the transmission should be good for at least another 30K miles if it was not abused. I'm always hesitant to get into the "while I'm in there..." trap, but if transmission wear is questionable, this would be the time to address it. Link to comment Share on other sites More sharing options...
NTX5467 Posted March 24 Share Posted March 24 14 hours ago, Aaron65 said: Didn't the 231 change to even fire around '78? You're right, now that I think about it. Link to comment Share on other sites More sharing options...
NTX5467 Posted March 24 Share Posted March 24 NOW we know why the engine was in the trunk, apart. As I recall, at about 65K, IF the engine had not gotten the best of care (as to timely oil changes and such), that's when the bearing issues started to appear. As prevalent as that engine was back then, many auto supplies kept the crank kit (crank and bearings) in stock. At least in the larger areas. It was always the middle main bearing where the problems were. For the reasons I mentioned above. So the engine got removed, torn down, then "archived" when the wear issues were known. Being where you are located, that was probably the easiest thing to do. Balancing? Not if the pistons are still the stock pistons and the casting numbers on the cranks match. Aftermarket pistons are usually a little heavier than the stock pistons, so that is when balancing is recommended. Which is one advantage to using OEM parts rather than aftermarket. GM pistons were the same weight from std size to +.030" over-size. But the OEM pistons were like $60.00/each compared to $15.00 for the good aftermarket ones. As to shipping, IF you want anything heavy shipped individually, I have no doubt the shipping charges can be what you mention. IF you can find a "freight consolidator", they can add it to an existing container they have coming your way, which might result in lower shipping costs. There are a lot of USA cars in EU. Networking with some of them might yield a better way to get something like a crankshaft shipped to EU. A Chrysler group might be contacted via www.bbtr.de . Plus various USA-brand and mixed-brand car clubs, too. Hopefully, somebody might have a connection. Thanks for the additional information, NTX5467 Link to comment Share on other sites More sharing options...
RivNut Posted March 24 Share Posted March 24 (edited) IF you’re considering a new engine, you might try to figure out what it would take to put a 350 Buick in the car like they did in 1979. Or even better would be to drop in an Oldsmobile 403 small block. Same engine that Pontiac used in their 6.6 liter Trans Am. All Oldsmobile small blocks have the same external dimensions from their 260 through the 403. The 400 and 455 are Oldsmobile big blocks. All you’d ever want to know about Oldsmobile engines https://oldsjunction.classicoldsmobile.com/oldsfaq/ofeng.htm#ENG 1964 - 1990 Big Block or Small Block ('64-'90) Engine General Motors also used the 403 small block to power some of their motor homes. Edited March 24 by RivNut (see edit history) Link to comment Share on other sites More sharing options...
EmTee Posted March 25 Share Posted March 25 22 hours ago, RivNut said: IF you’re considering a new engine, you might try to figure out what it would take to put a 350 Buick in the car like they did in 1979. The best way to do this is with a 350 equipped parts car. Given this Riviera is located somewhere in the EU, that's probably not possible. The best (and least expensive) option in this case is probably to pull the motor and do the rest of the rebuild (i.e., the bottom-end). It sounds like the heads were recently rebuilt already. Link to comment Share on other sites More sharing options...
RivNut Posted March 25 Share Posted March 25 1 minute ago, EmTee said: The best way to do this is with a 350 equipped parts car. Given this Riviera is located somewhere in the EU, that's probably not possible. The best (and least expensive) option in this case is probably to pull the motor and do the rest of the rebuild (i.e., the bottom-end). It sounds like the heads were recently rebuilt already. I did not realize this guy is from the EU. That would make it tough. 1 Link to comment Share on other sites More sharing options...
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