oil pressure

[blackdog1]

What should the oil pressure be? At idle? At speed 2000-2400rpm? The truck is a 1979 1ton srw 400 sb. I'm having some problems with the engine. Oil pressure seems to be all over the place. It leaks some and smokes when first started. I check the oil frequently but twice now it has quit on me. When this has happened the first thing I notice is the oil pressure going down when I step on it. It usually quits very soon after that. Put a couple quarts of oil in it and it fires right up and seems to run fine again. I also have trouble keeping temps down while transporting the plow. I'm thinking of just pulling the motor for a 350. Any advice or opinion is welcomed. Thanks

[wyldman]

First off,you need an accurate gauge.The factory gauges aren't very accurate.You could also have a bad sending unit.Put an aftermarket oil pressure gauge on it to verify your readings.

Oil pressure at hot idle should be at least 5 psi minimum,if the motor has any chance of survival.10 psi is better.

Ay 2000-2400 RPM you should have 20-25 psi minimum.General rule of thumb is 10 psi for every 1000 RPM.

The smoke at startup is most likely valve stem seals,which can be replaced without major engine disassembly.

When it starts to quit is it actually out of oil ? What does the dipstick read ? How long does it take after you top it up before this happens ? A day\week\month ? How many miles ?

The oil pressure will go down when you step on it if the motor stumbles,and loses RPM.The loss of RPM cause loss of oil pump output,and the pressure drops.

Is it hard to crank after it quits ? If it is,it may be siezing up due to lack of oil.

You may have two separate problems.One with oil consumption\leaks,and the other with the stalling.

[thesnoman]

Originally posted by blackdog1
What should the oil pressure be? At idle? At speed 2000-2400rpm? The truck is a 1979 1ton srw 400 sb. I'm having some problems with the engine. Oil pressure seems to be all over the place. It leaks some and smokes when first started. I check the oil frequently but twice now it has quit on me. When this has happened the first thing I notice is the oil pressure going down when I step on it. It usually quits very soon after that. Put a couple quarts of oil in it and it fires right up and seems to run fine again. I also have trouble keeping temps down while transporting the plow. I'm thinking of just pulling the motor for a 350. Any advice or opinion is welcomed. Thanks

Older small blocks usually idle with about 30 PSI of more when tight but anything below 15 to 20 PSI true pressure at idle is a sign of worn bearings or oil pump or both. At working speed of about 2000 RPM and above you need at least 30 PSI for the engine to hold up under heavy load with 40 PSI prefered, any more pressure than this is not realy needed for most uses. Anything less is slow death no matter what anybody tells you especailly at higher RPM's. As suggested above check pressure with a remote gage and if low before you pull engine, drop pan and check rod bearing and mains as well. It is fairly easy to replace bearings in truck if need be and changing them can make a world of difference in oil pressure too especailly if mains are worn. Make sure you are not using 5w30 in a worn engine and you might try a good grade of 15W40 in it too as it plays better in worn engines oil pressure wise. On the heating problem, your clutch fan is not working correctly. Replace it and it should cure that problem.

[blackdog1]

Wyldman, Thanks for your reply. The pressures look in the low but acceptable range based on junk factory gauge.The 1st time this happened was a bit different...Feeling a little lazy and way short of time I got an oil change at a local JiffyLube on the way home that night was the first time it quit 12:30 am in the middle of nowhere! On inspection the problem was that the oil filter was hanging on by a thread and I had lost just about all my oil. Now this has occured again with no apparent reason like the above. Could some damage occured the first time?It cranks right up after you add just 2-3 quarts of oil.There also is no noticeable stumble on acceleration. It also idles VERY rough at startup some times with the before mentioned medium grey smoke lasting longer. Thanks for your help guys. I decided to keep this truck for a few years and invest some money in it. I need to make it reliable before the snow flies. I may just drop in the 350. I have access to 2 solid 4 bolts and a more expensive bored and stoked balenced and blueprinted.Thanks again.

[wyldman]

Find out where the oil is going.Is the filter gasket blown off now after the filter came loose ? An engine shouldn't just use 2-3 quarts of oil all of a sudden.The engine may not be damaged yet,but it will be if you keep driving it that way.

[thesnoman]

If this is a plow truck, I would try to fix existing engine. If it were a newer truck, I would invest more money. A Jiffy Lube or Quick lube might have put in 5w30 which has no bussinees in old worn engines. If you ran it out of oil even for a minute, you can do serious damage. If it stopped for lack of oil then it really should be changed as it has been damaged enough to seize even if for a moment. At this point I would drop pan and inspect lower end and lower cylinders for piston scuffing/melting from friction from lack of oil. If they look okay, you could put new bearing in it an get a few years of plow service out of it. Even a sickly 400 can run pretty good sometimes and not have to be at its best to out perform a 350 overall.

[towman]

you need to talk to the juffy lube that did your oil change, if the filter was not properly installed they need to make things right , we have towed countless number of vehicles from the quick lube places, they should stand behind their work, as far as having over heating with the plow on, if you are transporting it in the summer you will have a tough time keeping the tempatures down with the lack of air flow

[thesnoman]

Originally posted by towman
you need to talk to the juffy lube that did your oil change, if the filter was not properly installed they need to make things right , we have towed countless number of vehicles from the quick lube places, they should stand behind their work, as far as having over heating with the plow on, if you are transporting it in the summer you will have a tough time keeping the tempatures down with the lack of air flow

Good Point!

On the temps though a proper functioning clutch fan should fix that problem. I had a problem like that many years ago on my J20 when it was in the 30's and above when carrying a plow down the road. A new clutch fan cured it.

[wyldman]

Originally posted by thesnoman
On the temps though a proper functioning clutch fan should fix that problem. I had a problem like that many years ago on my J20 when it was in the 30's and above when carrying a plow down the road. A new clutch fan cured it.

There may be nothing wrong with the clutch fan at all.The plow can block\redirect enough airflow,so that the clutch fan never sees enough hot air to engage.

This is different for every vehicle\plow combination,but most will have a hard time staying cool carrying a plow around in warm weather.The older Chevies,and Ford's were notorious for that problem.Some even had a hard time in the winter.

Playing with the height\angle of the blade can help.to get just enough airflow to engage the clutch fan.A solid fan will help the problem,as it will pull air through the rad at all times,as it doesn't require a certain temperature to kick in.

[76chevyman]

I would of went to the oil change place. I remember when i worked at those places i was in the pits and all the new kids were up top puting oil and everything in. One timei did my part but the kid up top didnt put oil in it. The car came back about 4 hours latter, with a blown engine.
Manager came to me yelling and i yell back saying stupid i run the pits you show me how to check the oil with out pulling a plug from under a car and ill do it. They i said werent you the one that was suppose to keep a eye on this kids work?? LOL that shut him up.
Well i spent the next two days putting in a new engine. So the oil place should be giving you a new engine if the filter was hanging and you lost all your oil. But it also may be to late for you to do anything about it.

Rich:burnout

[thesnoman]

Originally posted by wyldman
There may be nothing wrong with the clutch fan at all.The plow can block\redirect enough airflow,so that the clutch fan never sees enough hot air to engage.

This is different for every vehicle\plow combination,but most will have a hard time staying cool carrying a plow around in warm weather.The older Chevies,and Ford's were notorious for that problem.Some even had a hard time in the winter.

Playing with the height\angle of the blade can help.to get just enough airflow to engage the clutch fan.A solid fan will help the problem,as it will pull air through the rad at all times,as it doesn't require a certain temperature to kick in.

I disagree, replacing mine fixed it and it never came back. I can hear the one on my K3500 sometimes even when it is cold outside when plow is on it in transport. Temps stay steady regardless. If radiator is hot , the clutch will be hot too even if airflow is limited because what little air there is will be hot. Change the clutch assembly because it is not working or calibrated correctly.

[blackdog1]

Thanks everyone. The problem transporting the plow is a winter time problem as well,even with the plow just a couple inches off the ground. I never went back to the oil change place because I figured the internal damage if any would be too hard to prove. That's what you get for watching your gauges and paying attention. I sometimes think I should have run it hard and blown it. Then I wouldn't have these problems now...oh well. Right now I need to fix these problems so I can have a productive winter. The truck is going to be looked at Saturday by a good mechanic that I trust. Thanks again.