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So I have a question for my engine Gurus out there. Now to start this had been happening intermittantly for a few years now. And here is the jist of it. I have a 72 Cutlass Supreme 350 4BBL. and it is stocked with the Non Rallye gauge ( idiot lights ) And I am using Lucas classic car,Zinc 10W-30. When I am driving the car and the engine has warmed up, the oil gauge starts to flicker a little when I am stopped at a light, barely visible. As soon as I accelerate the flickering stops. I replaced the oil pressure switch yesterday because the flickering had started to become more quick and brighter. Tonight I went to a cruise about 4 miles away. I had only gone about 3/4 miles and the light begins to flicker while I was stopped at a light. About a mile from the cruise it became almost constant and bright unless I put the car in Neutral and increased the RPM's. When I got to the cruise and opened the hood there was a good amount of heat coming off the engine,and it smelled hot but the water temp was fine. All the way home from the cruise, I had to throw the car into neutral at every light ( 7 total ) or the warning light would stay bright and constant. So Monday I will go to my Mechanic and have him do an oil pressure test at the engine. Could be as simple as a bad NAPA switch or wrong pressured switch for the engine. So first question is Does anyone know what the correct oil pressure should be for this engine? And secondly if it is not the switch what would be the next part to check for: Sump pump, Oil pump. Head ports should not be fouled since I would start it and bring it to temp and run 15/20 mins every 3 weeks during the Winter. The engine only has 36,000 miles on it since it was rebuilt in 2006. But I had added 1970 pistons, but I kept the stock cam configuration. I also went from single exhaust to 2.5 dual stainless exhaust.
Sorry to be so long winded but needed to give you the back story. for proper responce.
Thanks All....... Stay Safe....Stay Sane ! Tony
Last edited by ragtopblue; May 16th, 2020 at 07:29 PM.
Reason: spelling correction
I'd like to see at least 10-15PSI at a hot, correct idle speed. The switch closes and turns the light on at about 5PSI.
Find the problem before driving it much if at all. Did the problem always occur following the engine work? I'm wondering if an oil galley plug was left out during assembly by the distributor hole or the timing chain. These are not solid plugs, they have an orifice that oils the distributor and timing chain. The oil pump could have come loose or the sump pickup is loose.
Thanks Sugar Bear, No sound issues pinging or pops. No it has been intermittant over the ten years. I'm thinking bad switch or sump screen. Plus to light weight of an oil. Going to do a Pressure test on Monday and go from there !
The stock oil pressure sender will close and illuminate the light when the pressure drops below 4-7 psi. The actual setting will vary with manufacturing tolerance. If the light is flickering, chances are that with hot oil and worn bearings or pump, your oil pressure is low. What weight oil are you using?
Hi Joe,
So for the past 4 years I have exclusively been using Lucas Classic Car w/ Zinc 10W -30 in the car. When the car is in storage I use Stabil in the fuel. And during the driving season I also use the Lucas Ethanol treatment and 89 methonal fuel. I just replaced the oil back in December before I put the car away for the Winter. The engine was rebuilt in 2007 and with 70 pistons and a stock cam. When I take the car back to the shop this week to do a pressure test I will change the oil again and go to either a straight 40 or a 20W-50 and see what happens at that point.
since the car will be up on the lift we might also drop the pan and inspect the Sump screen.
Why not 10-40? 10-30 is thinner at hot, the switch as joe alluded to could be a little higher than the possible low of 4psi.
the 20-50 will probably make a difference, I agree an oil psi test is a good idea, 10 psi at idle is not unusual, you definitely want 30-40 psi at cruise.
you can add an oil psi gauge easily to monitor the pressure under various conditions.
typically starting and running in the colder winter months does more harm than good, when I park my car in fall I change the oil take out the battery, top off the tank and use stabil and don’t touch it again until spring
Attached pictures show an oil pressure gauge and original oil pressure sending unit combo. A good friend in this Club (dc2x4drvr) showed me how to do this to combine the 2. Parts source Home Depot.
Soooooooo,
I'm still in limbo. I purchased another Oil pressure sensor switch and installed it making sure it was cross referenced with the original GM number. I installed it and started the engine and let it warm up. No flicker on the idiot light gauge. Then a light flicker, I put the car into drive and the Poil pressuer light once again came back on nice and bright ! At this point I shut the engine off, took out the oil pressure switch and installed the adapter and oil pressure gauge that my mechanic lent me. With the engine still warm and at idle the gauge was reading around 6 + pounds. Since I had the air cleaner assembly off I turned up the idle 3/4 turns and the pressure sat at about 7.5/8 pounds. I shut down and checked the new NOS dipstick ( same lenght as the original one in the car. It read about 1 qt above full. My fault from when I added an extra quart when the light started acting up. Right now I'm running Lucas Hot Rod- Classic car zinc 10w -30 If I can get it to the shop tomorrow I'll drain the oil and add GTX 10w - 40 oil and also a Qt of 50w break in oil and see what happens ! If this doesn't resolve the issue I'm not surewhat the next step will be, check the heads for blocked ports. Pull the intake manifold and check the valley pan. All the steps to trouble shoot the top end before I have to wrench up the engine and drop the pan ! Any thought regarding the sensor wire to the gauge? Could it be giving a false read?
Your intake and heads really have no effect on oil pressure, nor does having an extra quart of oil. A mechanical gauge should give the correct reading. If you are going to change the oil anyway, you might try 20w-50 instead of 10w-30. It will increase your oil pressure and provide more protection. If that doesn't have a significant impact, you are looking at bottom end work........
I merged your new thread and the old one as there was already discussion on your issue.
I would not put the gtx oil in there and definitely not the breakin oil. Use Valvoline VR1 racing oil is has a friction package that's perfect for a flat tappet cam. If the engine is not making any funny knocking or tapping noises, I would leave the mechanical gauge in and monitor the pressure for a bit after the oil and filter change.
Thanks oldcutlass,
But the manual oil pressure gauge kit was just a Pressure test gauge from the shop with a fitting and rubber hose and pressure gauge, Not a maual gauge on the engine or in the dash. Though I am going to be installing a rallye gauge during the Summer, I hate the idiot lights. Ok I will take back the 10w-40 GTX and get the VR1 racing oil. I rebuilt the engine back in 2007 and used 1970 pistons but kept the stock GM cam configuration.The engine only has 37,000 miles on it since the rebuild. Only odd noise from the engine is a slight exhaust leak that I need to trace. I think the Tranny shop didn't seat the up pipes to the exhaust manifolds properly.
After changing the oil and filter, test the oil pressure warm at idle and 2000 rpm's and post the reading. There might not be a problem with the engine.
Soooooooo,
Yesterday I jacket the car up, drained the 10w-30 out. Tightened the pan bolts aside from the ones behind the starter motor and trans inspection shroud. There was oil leaking from that, at its base. Not confident enough to drop that, I am not a mechanic. Replaced the oil with 20w-40 GTX high mileage and two bottles of STP oil additive ( sludge ) ! lol. Put in fresh 89 Octain gas. Started the car up and everything was fine. Drove it from Frazer 3 miles down to Exton Mall. Turned around and at the first stop light the low pressure warning light came back on from flicker tho bright red. Dropped it back into neutral light goes off. Back to drive and porceeded on to the next stop light. Light came back on again and I left the car in drive and light became constant , no flicker. This process continued for the next four lights in the same fashion. Brought it home and let it sit in the driveway for an hour. Started it back up and went to put it back in its parking spot. In a matter of 40 seconds even with the engine cooled down the light came on in drive and reverse. Long story short I have a call into a reputable engine and performance shop to take it in hopefully next week. This sucks !!!! As stated before I had the engine rebuilt back in 2007. The engine only had 113,000 on it and my Dad always put a lead additive in at fill ups since it didn;t have the hardened seats in it at that time. I had them added during the rebuild along with the 1970 pistons and it was bored 0,30 over. Even the engine shop wondered why I was having it rebuilt back them since they said the block looked great no scoring or bad piston rings. Aside from the pistons I did not change anything from what the engine was born with. I did two years later add 2.5 dual exhauxt to it. i have always ran with a zinc additive oil Lucas Hot
Rod Classic 10W-30 and Lucas ethynol treatment additive in the fuel. And Stable in the tank over the Winter with 20 minute runs every 3 weeks. So suspision is at this time the oil pump is failing. Before I changed the oil I did a mirror test from the dip stick and the oil was slick without contaminate smell I>E fuel or coolent. there were no micro shavings in it and no bubbles. See pictures.Sorry I tried to clean the mirror as best as possible, And the drag was done with a business card. I will also include an engine run video pre oil change. The odd sound is coming from the water pump or alernator area. But no voltage or water temp problems. The compressor was just installed in the fall along with the pulley, before it went into Winter storage
Have you actually checked the oil pressure with a mechanical gauge when the light was flickering?. That's the first thing you need to do. If you have low oil pressure then you have some serious and expensive work to do. Most likely a regrind of the crankshaft and new bearings and oil pump. Only trouble is you are entering MAW territory, while the engines out Might As Well......
If your engine is in good working order you don't need snake oil -pun intended- additives, be sure to use an oil formulated at the factory with enough zinc for your flat tappet engine.
Hi Roger,
Yes I used a mechanical oil pressure gauge hooked up where the oil Pressure sending unit is just behind the water pump. Pressure was 6/7 pounds at warm idle at 1800/2000 rpms. New oil pump was installed when the engine was rebuilt in 2007. New stock ratio cam stock GM heads etc.
Hey Ralph no all new parts were installed when the engine was rebuilt back in 2007. New pistons 70 rings, cam, lifters rods valves ETC. engine only has approx 37.000 since rebuild 13 years ago. Average per year has been 2,500 per year. longest distence it has been driven is around 160 miles.
When the engine was rebuilt, was the crank ground and new bearings installed? You said it had 113,00 miles on it back then and you have since put 37,000 miles, for a total of 150,000 miles.
Soooooooo,
Yesterday I jacket the car up, drained the 10w-30 out. Tightened the pan bolts aside from the ones behind the starter motor and trans inspection shroud. There was oil leaking from that, at its base. Not confident enough to drop that, I am not a mechanic. Replaced the oil with 20w-40 GTX high mileage and two bottles of STP oil additive ( sludge ) ! lol. Put in fresh 89 Octain gas. Started the car up and everything was fine. Drove it from Frazer 3 miles down to Exton Mall. Turned around and at the first stop light the low pressure warning light came back on from flicker tho bright red. Dropped it back into neutral light goes off. Back to drive and porceeded on to the next stop light. Light came back on again and I left the car in drive and light became constant , no flicker. This process continued for the next four lights in the same fashion. Brought it home and let it sit in the driveway for an hour. Started it back up and went to put it back in its parking spot. In a matter of 40 seconds even with the engine cooled down the light came on in drive and reverse. Long story short I have a call into a reputable engine and performance shop to take it in hopefully next week. This sucks !!!! As stated before I had the engine rebuilt back in 2007. The engine only had 113,000 on it and my Dad always put a lead additive in at fill ups since it didn;t have the hardened seats in it at that time. I had them added during the rebuild along with the 1970 pistons and it was bored 0,30 over. Even the engine shop wondered why I was having it rebuilt back them since they said the block looked great no scoring or bad piston rings. ----->Aside from the pistons I did not change anything from what the engine was born with.<----- I did two years later add 2.5 dual exhauxt to it. i have always ran with a zinc additive oil Lucas Hot Rod Classic 10W-30 and Lucas ethynol treatment additive in the fuel. And Stable in the tank over the Winter with 20 minute runs every 3 weeks. So suspision is at this time the oil pump is failing. Before I changed the oil I did a mirror test from the dip stick and the oil was slick without contaminate smell I>E fuel or coolent. there were no micro shavings in it and no bubbles. See pictures.Sorry I tried to clean the mirror as best as possible, And the drag was done with a business card. I will also include an engine run video pre oil change. The odd sound is coming from the water pump or alernator area. But no voltage or water temp problems. The compressor was just installed in the fall along with the pulley, before it went into Winter storage
6-7 lb/psi at 1800 rpm is very poor. If the crankshaft has 150k behind it without attention then is past due. The warning light is doing its job, warning you all is not well with the lubrication system.
Planning a teardown and addressing the issues will be far cheaper than waiting until it goes bang......
∆∆∆Planning a teardown...∆∆∆ Unfortunately that is the answer @ 6/7 psi @ 1800-2,000 rpm's. It could be many different things but your going to be better off figuring it out. Could be simple e.g., an oil pump, loose galley plug or major such as a crank. Driving it like that isn't good for it, I'm not saying not to gently bring it home but no regular usage.
Don't bother to cut the filter up. If you find no evidence of bearing debris, then what?. You already know you have seriously low oil pressure. Time to pull the engine and start taking it apart to see what needs doing. Could be the bearing debris has been removed in previous filter changes.
Why wouldn’t you want as much info as possible before tearing into the engine? If there is no debris, but low oil pressure, that would suggest oil pump issues. Is the oil pump sitting flat on the main bearing cap? Or maybe pressure regulator valve stuck open?
Can the pan be removed while in the car? If so try a little plastic gauge on the mains and rod This will tell a lot. You can tell I'm not a A body guy and usually refrain from posting on much A body related stuff but it seem like it would be so much easier to do a bearing check in the car...... Verry lost in the fifties.... Tedd
The pan will come out, it’s not easy. Like I mentioned earlier, if the filter was clean of bearing and metal, I would be willing to remove the pan with the engine in for oil pump or other inspection. If the filter is full of debris, just pull the engine.
the pan will come out, it’s not easy. Like i mentioned earlier, if the filter was clean of bearing and metal, i would be willing to remove the pan with the engine in for oil pump or other inspection. If the filter is full of debris, just pull the engine.
I've been watching your thread and this type of problem/scenario gives me a dreaded feeling like some of the problems I have dealt with on old cars. You spent good money and expected much longer service from your engine when you had it rebuilt... Anyway as others have said you are going to have to take it apart. There are lots of reasons for low oil pressure including cam bearings. Keep us posted- Good luck.
May 16th, 2020, 07:22 PM
Oil pressure warning light.
Oil pressure warning light update.
