Oil Pressure Problem 351w
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=16371
Printed Date: April-28-2024 at 7:00am
Topic: Oil Pressure Problem 351w
Posted By: MorganB
Subject: Oil Pressure Problem 351w
Date Posted: January-26-2010 at 1:04am
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Hi everyone
Just over the last few trips i have had a couple of problems with my oil pressure in my 83SN its fine for the half hour or so (40psi) then it drops way of to like 5 at idle and 20 running, the 1st time i saw it i went straight home checked oil level, was a bit low but nothing to cry home about, so i topped it up (15w40), ran it on a hose for about 15 min and everything was normal! so went out again last night and same again after a while it dropped off, not as far as the 1st time but still under 15 at idle and max of 30, everything sounds normal to me no major leeks (always had 1 small one out of the main end seal) what do u think could be the issue? the engine has done 1100 hours so its not in mint condition but it starts first pop every time has heaps of power for what i need and i never run it much over 3500rpm in fact most of the time only about 1800rpm. |
Replies:
Posted By: SS 201
Date Posted: January-26-2010 at 8:41am
| I am assuming you changed the filter too, If not do so. |
Posted By: SNobsessed
Date Posted: January-26-2010 at 10:53am
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Morgan - It sounds to me that your bearings are at the end of their life (too much clearance). You might want to switch to 20W50 for the short term, then start a fund to rebuild the engine. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: 8122pbrainard
Date Posted: January-26-2010 at 11:03am
Or go to a straight weight 40. The pressure dropping off on a high hour engine is typical when using multi vis oil after it gets hot. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
SNobsessed wrote:Posted By: eric lavine
Date Posted: January-26-2010 at 12:13pm
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i dont condone Lucas, but it wouldnt hurt....run it in my car to keep the oil pressure light from coming on. thats a mechanics fix btw. I look at it this way its not going to get any better and why spin a bearing and create yourself more problems ------------- "the things you own will start to own you" |
Posted By: SS 201
Date Posted: January-26-2010 at 6:08pm
| What the Lucas does is keep the viscioty of the oil up. Bearing clearances get bigger and so does the pumps,Heavy oil does help, however its flows heavier so the quality of flow of the oil is comprised a bit that's why they use a multi vis oil. |
Posted By: behindpropeller
Date Posted: January-26-2010 at 7:55pm
Put a mechanical gauge on the engine and verify that you actually have low pressure. 1100 hours isn't much. ------------- |
Posted By: SNobsessed
Date Posted: January-26-2010 at 9:17pm
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BP, good point. I once had a loose connection on a sender & the gauge would vary depending on speed (vibration). ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: MorganB
Date Posted: January-26-2010 at 9:24pm
| Hmm Seams everyone has the same conclusion i have come up with, bottom end bearings! can i just replace those? or would it be a waste of time? the engine just runs so happy dont relay wana spend money on complete build, i don't think 1100 was a massive amount of hours. will have to look out for this LUCAS stuff see if i can get it here. also will change to 20/50 see if that helps for now! still got at least another 2 months of boarding to get in this summer! |
Posted By: SNobsessed
Date Posted: January-27-2010 at 1:00am
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Check out Jbear jr's post. Sounds like he put new bearings in without much fuss;
http://correctcraftfan.com/forum/forum_posts.asp?TID=14757&KW=&title=rear-main-on-jbear-boat - lower end rebuild ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: kapla
Date Posted: January-27-2010 at 1:03am
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1100 is not that much on this engines..mine actually went almost 2k before one of the heads cracked..could have lasted some more time if that didn't happen... ------------- <a href="">1992 ski nautique |
Posted By: critter
Date Posted: January-27-2010 at 2:39am
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I too would put a mechanical guage on before I tore that motor down. It is too easy to pick up and install a mechanical guage not to verify the suspected pressure drop. Just mount it under the motor cover and check it often to verify your concerns. If the oil pressure is ok on the mechanical guage, then you need to be looking elsewhere. ------------- 1980 Ski Nautique 1966 Barracuda |
Posted By: eric lavine
Date Posted: January-27-2010 at 10:26am
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1100 isnt that much if the oil was changed regularly, its funny sometimes you tear into a 500 hour engine and it looks like 3000, but try the mechanical guage first then decide which way to go. ------------- "the things you own will start to own you" |
Posted By: skicat2001
Date Posted: January-27-2010 at 1:40pm
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What is standard pressure readings? If I can remeber mine runs at 20psi at idle and above 60-70 while running.. ------------- 1985 CC 2001-SOLD Lee Michael Johnson |
Posted By: kapla
Date Posted: January-27-2010 at 3:08pm
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In the case he decides to put a mech gauge..were should it be plugged? I guess that will need to put the gauge in place of the oil sender?
------------- <a href="">1992 ski nautique |
Posted By: abolton
Date Posted: January-27-2010 at 4:03pm
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Did anyone else see the episode of Horsepower TV where the drilled into the oil passage in the back of the block and ran copper tubing up to the front of the block and tapped into the oil passage? They where said the racers do it all the time on the Ford 351's because of week oil at the front end. ------------- ABE |
Posted By: 79nautique
Date Posted: January-27-2010 at 4:37pm
either tee into the oil pressure switch/sender or remove it and install the gauge start it up and let it get hot no need to go anywhere to see the oil get hot and loose pressure, Driving it is only going to get it hotter quicker and so it takes an extra couple minutes sitting at the dock or on the trailer to find your answer. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: GottaSki
Date Posted: January-27-2010 at 5:05pm
Never heard of any weekness with the W oil system. And weak at the front? where the pump is? Similary skeptical. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: TRBenj
Date Posted: January-27-2010 at 5:17pm
Im no expert, but I thought I had heard of something along those lines regarding the Ford 460. Maybe thats where the confusion is? ------------- |
Posted By: MorganB
Date Posted: January-27-2010 at 7:55pm
Yea we have had the sump off once wile i had the engine out to paint the bilge and my mechanic was quite happy that it was real clean in there and the oil looked good and so on, but once again it hasn't been performing max rpm 4200 (only had it there once, also at that rpm after bout 1 minute i could hear the tapits then it would start to back itself off a bit then eventually blow back through the carb? does anyone know what that could be? (never tried that again happy to keep rpm low wake boarding) Thanks for the link but does anyone know of a more detailed post on someone pulling the bottom end off with photos and so on? Thanks for all the responses im getting some good ideas |
Posted By: critter
Date Posted: January-27-2010 at 10:42pm
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This site has some pictures that you can enlarge to get better views.
http://www.fast351.com/cartech/enginerebuild/index.htm - Rebuild If you are thinking of only doing the main and rod bearings without pulling the heads, it can be a bit more difficult. ------------- 1980 Ski Nautique 1966 Barracuda |
Posted By: Waterdog
Date Posted: January-28-2010 at 5:11pm
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It's tricky rolling the main thrust bearing out of the block and rolling the new one in. The first one I did, a freind gave me OJT on, now I can do it. ------------- - waterdog - http://www.correctcraftfan.com/diaries/details.asp?ID=3896&sort=&pagenum=2&yrstart=1978&yrend=1978" rel="nofollow - 78 Ski Tique |
Posted By: MorganB
Date Posted: February-02-2010 at 7:41pm
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Update:
Put a diff version of that Lucas stuff in, it helped a lot, still only getting about 10psi at idle but 40 wile running so will do me out for the rest of the summer i hope!!! Once again thanks for all the help! |
Posted By: Greg_SA
Date Posted: February-04-2010 at 2:58pm
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Hi,
This last weekend, I noticed my oil pressure had suddenly dropped by about say 15psi (idle or while cruising). It is normally around 30psi idle and 70psi cruising speed). My oil level was also a bit low (at the add oil mark), so I topped it up (not much was needed to get back to the full mark), but the pressure isn't what it used to be (say 15pis idle and 40psi running). I hope that the very short time the oil level was a bit low couldn't have done damage to something? I'm wondering if the oil markings on my dip stick are actually correct, maybe I have the wrong dip stick (eek). I'm just wondering what I can check/do: * Replace oil filter? (in case this has some blockage?) * Remove and clean the sender unit? Does anyone know what I can clean with? Some alcohol? * Measure resistance of sender unit (240 ohms = 0psi, 33 ohms = max psi, 100 ohms is about the middle). * Test with mechanical pressure gauge? A local mechanic mentioned that it can be the bypass (relief) valve of the oil pump is stuck open (gone sticky)? As I understand, the oil pump diverts oil back to the sump to regulate the oil pressure from going too high. MorganB, did you try anything listed above, or just run the Lucas oil? Any help would be great. Cheers Greg ------------- 1989 Ski Nautique (SN2001) |
Posted By: MorganB
Date Posted: February-04-2010 at 9:02pm
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Hi Greg no i did not do any of that was always planning on getting another gauge and put it on but were using the boat every second day so have yet to have a chance to do so!
the Lucas seamed to make things abit better to be comfortable running it!! A little strange that both of us all of a sudden had a problem after letting the oil get a bit low! 
|
Posted By: SNobsessed
Date Posted: February-04-2010 at 9:11pm
Greg - It doesn't sound like wearout - I'm with you, sounds like the relief valve has dirt in it. Or maybe the oil pump is going out. How many hours are on your oil change? I notice a drop (but not quite that much) after about 40 hours. Test with a mechanical gauge before you tear into it! ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: Greg_SA
Date Posted: February-04-2010 at 10:47pm
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Hi,
Thanks for the feedback. I do my oil change around every 50 hours. It has been about 40 hours since the last change! Maybe I should just do a oil change again, now - it can't hurt? I'll definitely test with a mech gauge - just need to find one locally (I'll call some auto shops). Thanks again, Greg ------------- 1989 Ski Nautique (SN2001) |
Posted By: critter
Date Posted: February-04-2010 at 10:57pm
Walmart has them along with most Autoparts stores. Just get a cheap one as you will be removing it after correcting the problem and it will stay in your workbench for the next time you need it. ------------- 1980 Ski Nautique 1966 Barracuda |
Posted By: Greg_SA
Date Posted: February-08-2010 at 5:11am
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Hi,
I did an oil change (and oil filter) this weekend (the last oil was only 30 hours old). When cold, the oil pressure was around 80psi... and as it warmed up, it dropped to around 55 to 60 psi when cruising. Idle was around 30 (in gear) or 40 (neutral) psi. It stayed like this for around 10 minutes of cruising. Later the next day, I took a long cruise at say 3000rpm for around 20 minutes... I noticed the oil pressure was a bit lower, around 50 psi. At idle (neutral) it was 30 psi, but then after idling in neutral for about 2 minutes, it rose to 40 psi. At one point, it was at 50psi after a l0ong time idling. Could these differences be due to a difference in oil temperature? I got a mechanical oil pressure gauge, but never got a chance to test it - I'll try next weekend though. Regards, Greg ------------- 1989 Ski Nautique (SN2001) |
Posted By: SNobsessed
Date Posted: February-08-2010 at 10:47am
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Greg - Your pressures are very similar to what I get.
I'd say your problem is solved. The differences in pressure are from the oil temperature changes affecting the viscosity. The oil takes a while to cool down after you go back to idle. Remember the block stays pretty constant from the lake water cooling but the pistons get very hot from the constant load at higher RPMs. The oil cools the pistons off. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: Ryan351w
Date Posted: February-08-2010 at 3:31pm
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just a little rule of thumb...10psi per 1,000 rpms.
The better the machining the less pressure needed. I talked to a head guy at Melling and he was telling me that the NASCAR engines run only 70-80psi. Granted these motors come apart every race, regardless of that the motor would take itself apart if there wasn't enough pressure. Remember these motors turn over 9,000! Another little trick, diesel oil. I run it in everything, 500hp mustang, aurora, boat, diesel truck. The diesel oil is awesome. My buddies dad runs it in his blown 340, in the motor and the blower. It has alot of additives in it that were takin out that protected metal-to-metal contact. It was mainly there for lifters to cam lobes. But when roller lifters and OHC's came on the scene they decided that it wasn't needed anymore. Luckily diesel motors still use flat tappet lifters so those additives are still needed. Another piece of info-pump placement in the motor packaging itself has no effect of where you will get higher or lower oil pressure. The oil galleys are drilled where they are drilled. They feed the mains and rods then depending on the motor it will pull from the main galleys to feed the lifters/cam/push rods. So running a "jumper" line from the front to back or vise versa is helping a bad spot (low oil pressure) in the motor. |
Posted By: TRBenj
Date Posted: February-08-2010 at 3:52pm
Careful! Most diesel oils have removed the heavy metal additives to comply with the new emissions equipment. This change has come about within the last few years. Only a select few grades still have the required ppm of ZDDP that flat tappets need. Rotella straight weights and Valvoline Racing VR1 still have pretty high levels of the stuff- I run the VR1 in all of my flat tappet boats. ------------- |
Posted By: GottaSki
Date Posted: February-08-2010 at 3:57pm
Consider checking your sources. You may have the order backerds, the failing cayalysts and extended gov'ment mandates for emissions warrantees drove the reduced zinc oil blends that neccessatated the roller cams, not the other way around. Automakers didn't just convert their fleets roller to be kewl. While i agree the oil is better, the diesel oil has much reduced zinc over the last two years, so be wary as this progresses. This is due the same driving forces. I think you are mistaken about the flat tappet lifters. I can report GM diesels haven't used flat tappets since the 350 olds/diesel abortion almost 30 years ago. Even the old detroit two-strokes are roller. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Ryan351w
Date Posted: February-08-2010 at 6:07pm
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Gottaski-http://www.cumminsdieselspecs.com/67.html My source. And in non-diesel engines rollers just allowed them more aggressive lobe profiles which = more power. Less duration/more lift. Idles better too. Possible friction advantage could be part of it too.
There have been roller motors for a LONG time in the OEM field. I know in the mustang the roller was introduced in 85. Dodges' in 91. Oil changed in early 2000's TRB-That’s exactly the oil I’m referring to. Rotella-T is a diesel oil. And when I buy generic stuff, I make sure they have the same mount of additives. |
Posted By: 8122pbrainard
Date Posted: February-08-2010 at 6:30pm
Ryan, Glad you stated the Rotella but keep in mind that it's the straight weights that have the ZDDP. I'd hate for someone with a flat tappet engine to be misinformed. The ZDDP has been researched and discussed at length here. I like Tim run the VR1 in all my engines. BTW, I am hearing about cam failures on old engines. A couple from flat head Hercules owners who were using what they thought was "good" oil!!!! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Ryan351w
Date Posted: February-08-2010 at 10:04pm
| On a quick search while cooking I found that the Rotella with "triple protection" has..."Multigrade Oil SAE 15W-40 with Triple Protection Technology, our API CJ-4/SM specification product, typically contains about 1200 ppm zinc and 1100 ppm phosphorous as manufactured." |
Posted By: Greg_SA
Date Posted: February-09-2010 at 5:15am
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Hi,
Thanks very much for the responses... So it sounds like my old pressure is okay, but I'll double check with the mechanical gauge, and keep an eye on it :) Regards, Greg ------------- 1989 Ski Nautique (SN2001) |
Posted By: eric lavine
Date Posted: February-09-2010 at 11:04am
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many cam failures lately on the flats, 3 to count on rightie bbc's, not a good percentage since they were the only 3 i took apart this summer, there are zinc additives out there also and probably wouldnt hurt on top of the oil change, i was a skeptic, now im not ------------- "the things you own will start to own you" |
Posted By: GottaSki
Date Posted: February-09-2010 at 11:22am
Ryan since it appears you are a student of automotive trivia, you may find it interesting the GM/allison 6.2L diesel was roller for its introductory year of 1982, three years before the mustang 5.0 HO roller cam engine, and even the 350 olds abortion i spoke of went roller half in the latter half of its run in 1980. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: eric lavine
Date Posted: February-09-2010 at 12:05pm
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i recently took a 4.3 vortec apart, roller cam, roller lifters, a balance shaft, real potential for some power there, i see alot of them in boats already and pretty lean on the fuel useage. not recomending them for a ski-boat but was pretty surprised to see the roller rockers ------------- "the things you own will start to own you" |
Posted By: eric lavine
Date Posted: February-09-2010 at 12:06pm
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i was thinking of bolting 2 of them together though, a nice v-12????lol ------------- "the things you own will start to own you" |
Posted By: Preston01
Date Posted: October-09-2018 at 1:00am
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Hey y’all, I am experiencing the same issues on my 83FN. Would replacing the 160 degree thermostat with a 140 degree help with the viscosity? Any other suggestions? |