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OK - that is interesting - I was running 10/30, thermostat housing temp was 205 F and the oil was 220 F.
Pan off is as Far as I got tonight - The oil pick up is right on the bottom of the pan, where I expected it to be, that is the first thing to fix. Also - 4 quarts fills the pan to the baffle which is about 3/4" under the counter weight and corresponds to almost full on the dip stick.
Does this mean that with 6 quarts, oil is hitting the crank? Maybe your problem is aerated oil?
I had put an extra quart in to see if I was starving the engine - the oil pressure issue did not change - 4 quarts or 5 quarts, it did not matter (this does not include the quart in the filter so the total oil in the engine was 5 or 6.) Knowing this and knowing that a certain amount of oil is "in flight" it would seem you could run a bit more the 4 quarts in the pan and still have all the oil in the pan under the baffle.
This test tended to say that I did not have a problem with all the oil being in the valve covers - that leaves the issue to a leak someplace or a faulty pressure regulator or a pump with too much clearance.
On examination of the oil pump, the pressure relief piston seem a bit sticky and the clearance was quite tight. I cleaned the hole and wiped off the piston. Got some specs of dirt out and it slid more freely when I was done. I change the vertical location of the oil pickup screen, using the recommended clay method, to be exactly 7/16" off the bottom of the pan. I slapped the pan back on without even changing the gasket, and started some testing - Well, things started out looking pretty good - 10/30 Valvoline, 58 psi on start up at 1700 rpm on the choke idle cam. I ran the car while still on jack stands, up to operating temp, oil pan temperature as 215, and the idle oil pressure was over 20 - looking good! I took it out on the road.
The pressure was better, 45 psi at at 180 degree water temp and cruising speed - so I believe there was something going on with the bypass in the oil pump. I took it to 4000 in 3rd - about 70 mph and after 30 seconds or so I started to see the oil fluctuations again. The needle was bouncing around 40 and would drop ever couple of seconds to 30 psi. Also when I stopped the idle pressure was down to 12 psi again, but it would jump right up to 40psi if I blipped the throttle.
After a couple minutes of mild driving the idle pressure was up 15 psi. Don't know if this is because the oil cooled off or the high rpm had foamed it up and it had "un-foamed" ? Hmmmm .
- I have a stock oil pan - Am I expecting too much for a non- windage tray engine? So the fluctuation in my thinking is either foaming, or starvation via filling the valve covers. The 12 psi at idle tends to make me think foaming, but it could be both foaming and starvation.
- I don't see how a sticky bypass valve could cause the fluctuation - not that I'm an expert. If I put in a HV pump, I would think a starvation problem should get worse.
- I'm also thinking the pressure bypass valve is still a problem and may get worse when hot.
On examination of the oil pump, the pressure relief piston seem a bit sticky and the clearance was quite tight. I cleaned the hole and wiped off the piston. Got some specs of dirt out and it slid more freely when I was done. I change the vertical location of the oil pickup screen, using the recommended clay method, to be exactly 7/16" off the bottom of the pan. I slapped the pan back on without even changing the gasket, and started some testing - Well, things started out looking pretty good - 10/30 Valvoline, 58 psi on start up at 1700 rpm on the choke idle cam. I ran the car while still on jack stands, up to operating temp, oil pan temperature as 215, and the idle oil pressure was over 20 - looking good! I took it out on the road.
The pressure was better, 45 psi at at 180 degree water temp and cruising speed - so I believe there was something going on with the bypass in the oil pump. I took it to 4000 in 3rd - about 70 mph and after 30 seconds or so I started to see the oil fluctuations again. The needle was bouncing around 40 and would drop ever couple of seconds to 30 psi. Also when I stopped the idle pressure was down to 12 psi again, but it would jump right up to 40psi if I blipped the throttle.
After a couple minutes of mild driving the idle pressure was up 15 psi. Don't know if this is because the oil cooled off or the high rpm had foamed it up and it had "un-foamed" ? Hmmmm .
- I have a stock oil pan - Am I expecting too much for a non- windage tray engine? So the fluctuation in my thinking is either foaming, or starvation via filling the valve covers. The 12 psi at idle tends to make me think foaming, but it could be both foaming and starvation.
- I don't see how a sticky bypass valve could cause the fluctuation - not that I'm an expert. If I put in a HV pump, I would think a starvation problem should get worse.
- I'm also thinking the pressure bypass valve is still a problem and may get worse when hot.
thought appreciated
Aaron
I remember someone posting a similar problem, and I think I remember the problem was that there were some plugs missing at the front of the block behind the cam gear. Also, there is a plug somewhere in the back of a small block that needs to be in place. I don't remember where or why, but I remember forum member "Blockman" explaining it a few years ago.
Try an advanced search with low oil pressure, and posts by Blockman.
heres the deal,, when oil gets hot ,it gets thin and will bleed off quick like water ,, you need to have a passenger with you and monitor the oil pressure gauge , make a hard pull and run it thru gears and see if it drops when you have your foot planted up to 5500 rpm, if the oil pressure is steady thru the pull (not dropping less the 40-50 psi ) you should be good(for every 1000 rpm is 10 psi ) ,, ,,,if your concerned throw some 20/50 in it an see what it does ,, if its synthetic oil ,it is the most consistent thru all temps (personally its way to thin for my liking but us old dudes have to get with the times)
hey back in the day when ponitacs had the start up death knocks we used to put in 85/140 ,, talk about slow crank in the dead of winter ,, if starters could talk!!!! theyed be screaming
Put in a m55HV today to see what would happen - this pretty much rules out the pump and bypass system of the original pump. Started out with 70 psi oil went 50 hot cruise, pump fluctuated at 4000 rpm as before and under acceleration with hot oil, just pushing the peddle down in second gear, the pressure dropped to 20. Hot idle pressure with the HV pump is 15. With the HV pump, the scenario is basically the same, just everything happens much faster.
SO - I believe I have Leak some place in the engine that is allowing a bunch of oil to get pumped some place where it takes it's sweet time returning to the pan. I have comp cam lifters which I believe are oil limiting - need to check. I also have comp cam push rods, but they are just "tubes" The engine does not leak a drop of oil externally so a couple of plugs can be ruled out. I did not check that number 5 main - need to do that. I'm hoping it is not the cam bearings.
I would remove the intake and valve covers, use an oil priming tool with a strong drill and see if there are any abnormal oil paths or something holding the oil up top.
Put in a m55HV today to see what would happen - this pretty much rules out the pump and bypass system of the original pump. Started out with 70 psi oil went 50 hot cruise, pump fluctuated at 4000 rpm as before and under acceleration with hot oil, just pushing the peddle down in second gear, the pressure dropped to 20. Hot idle pressure with the HV pump is 15. With the HV pump, the scenario is basically the same, just everything happens much faster.
SO - I believe I have Leak some place in the engine that is allowing a bunch of oil to get pumped some place where it takes it's sweet time returning to the pan. I have comp cam lifters which I believe are oil limiting - need to check. I also have comp cam push rods, but they are just "tubes" The engine does not leak a drop of oil externally so a couple of plugs can be ruled out. I did not check that number 5 main - need to do that. I'm hoping it is not the cam bearings.
well I hope this isn't the case but I have seen this once before and it was a crack on the main journal in the block right at the saddle where the oil hole that feeds to the crank ,, when it got hot it would open up and loose pressure .. to took a while to find that one ,if it was a cam bearing that would be a issue from the first start up of the engine
I remember someone posting a similar problem, and I think I remember the problem was that there were some plugs missing at the front of the block behind the cam gear. Also, there is a plug somewhere in the back of a small block that needs to be in place. I don't remember where or why, but I remember forum member "Blockman" explaining it a few years ago.
Try an advanced search with low oil pressure, and posts by Blockman.
Gerry
ETA: I would try a new oil pump.
H, your thinking of my problem when I first came on the forum. New rebuild, forgot about plugs in front of engine under timing chain cover
Put in a m55HV today to see what would happen - this pretty much rules out the pump and bypass system of the original pump. Started out with 70 psi oil went 50 hot cruise, pump fluctuated at 4000 rpm as before and under acceleration with hot oil, just pushing the peddle down in second gear, the pressure dropped to 20. Hot idle pressure with the HV pump is 15. With the HV pump, the scenario is basically the same, just everything happens much faster.
SO - I believe I have Leak some place in the engine that is allowing a bunch of oil to get pumped some place where it takes it's sweet time returning to the pan. I have comp cam lifters which I believe are oil limiting - need to check. I also have comp cam push rods, but they are just "tubes" The engine does not leak a drop of oil externally so a couple of plugs can be ruled out. I did not check that number 5 main - need to do that. I'm hoping it is not the cam bearings.
Check front oil galley plugs under timing chain cover , may be missing one leading to oil pressure drop.
H, your thinking of my problem when I first came on the forum. New rebuild, forgot about plugs in front of engine under timing chain cover
Jack
Yes. The oil gallery plugs at the front of the block behind the timing set. If one leaks or is missing, thick oil will build pressure and the pressure will drop as the oil warms up. Pulling the water pump and timing chain & gears will expose the plugs for inspection.
A crankshaft with 0.010 under ground mains and standard bearings will also leak down and lose oil pressure as it warms up with similar symptoms.
Since you checked the mains, that leaves the oil gallery plugs. If the block was cleaned, and the oil galleries rodded and brushed, there is the chance a press plug failed to set and leaks or popped out, or threaded plugs were simply left out.
This is stock oil pan and pump on a new engine - 1000 miles. The oil pressure when hot is lower than I would like, but the oil viscosity (presently 4 +1 quarts of 10-30 non synthetic) is lower than I intend to run long term. Oil temp measured with laser thermometer pointed at the pan mid way up when hot puts the oil at 220 F. This is when it has been really working. At 220 degrees F the idle pressure at 900 rpm idle is 12 psi, and 3000 rpm cruise is 35 psi.
When cold start up, the oil pressure is 50 at idle, and drops as it warms up. When cold if I blip the throttle to 2500 rpm, the pressure will go over 60 psi.
So the issue, if I run it up to 4000 rpm cruise, the pressure will go to 40 psi at or around this oil temp (220 F) and then start of fluctuate (it starts bouncing down to 25) which I'm reading as oil starvation. Now I thought I got the oil pick up pretty close to the bottom of the pan, which I'm going to check. This oil fluctuation is really troubling me, and I'm thinking things need to come apart again, but I'm not sure where to start looking? Any one have a similar issue or better yet know what I'm up against?
Thanks,
Aaron
The first question I have I didn't see answered in here. If it was built by a reputable shop, why haven't you gone to them about the issue?
That out of the way, oil temperature at 220°f is well within specs. I used to run oil as high as 240°F in the race car. Typically it runs 20-30°F about water temperature.
A second option is on a Flint block, you can pull the plug above the timing cover and stick in an oil gauge. Pressure will be about 10 PSI less than the rear port.
Cavitation is about all that makes sense for it to drop at 4000 rpm.
One source for pressure loss is the distributor. Most never think about it, but if the distributor is an aftermarket and isn't fitting snug in the hole, oil can leak right past. And since you list a '65, if you have a '65 396 or you put in a '66 big block, there is a different rear cam bearing and a different distributor required. Many a shop has been stumped by this.
H, your thinking of my problem when I first came on the forum. New rebuild, forgot about plugs in front of engine under timing chain cover
Jack
Jack, when they forgot to put the plugs in the front of the engine behind the timing chain, were your pressure levels similar to what I'm seeing e.g. 10 is psi at hot idle?
The first question I have I didn't see answered in here. If it was built by a reputable shop, why haven't you gone to them about the issue?
That out of the way, oil temperature at 220°f is well within specs. I used to run oil as high as 240°F in the race car. Typically it runs 20-30°F about water temperature.
A second option is on a Flint block, you can pull the plug above the timing cover and stick in an oil gauge. Pressure will be about 10 PSI less than the rear port.
Cavitation is about all that makes sense for it to drop at 4000 rpm.
One source for pressure loss is the distributor. Most never think about it, but if the distributor is an aftermarket and isn't fitting snug in the hole, oil can leak right past. And since you list a '65, if you have a '65 396 or you put in a '66 big block, there is a different rear cam bearing and a different distributor required. Many a shop has been stumped by this.
This is the matching 300 hp 327 - actually tuned to be more like an L79.
I would love to find out that the distributer is wrong and I can replace it and the issue will be gone - I think it is original but the tack does read 10 % low. Will address that another time.
If I understand cavitation, that would infer a restriction on the input, do I have this correct? I'm running a stock pickup and have tried both a standard pump and a HV with similar drops in pressure. With the standard pump at 4000 rpm, it would drop 10 to 15 psi about once a second. Being horrified as I was, I did not do this for very long.
About the shop - This is supposed to be top notch place, lots heritage and from a performance standpoint, they nailed it. This is the first engine I have taken to them, and the first try was a disaster - but they re-rebuilt the whole thing. And here we are again with a different and less dramatic issue. I wanted to try to rule out the simple stuff before calling them, have done that know as far as I know. I will pull the engine again if that is what is required. I'm going to call them in the morning.
Last thing - I will look for that oil plug. So the oil pressure difference between the back of the engine and the front is more that 10 psi - likely it is a plug? Thanks for the advice.
Jack, why they forgot to put the plugs in the front of the engine, behind the timing chain, were you pressure levels similar e.g. 10 is psi at hot idle?
Aaron
When I found oil gallery plugs missing, the pressure was low in a similar manner. The front main and front oil pressure tap were low on pressure. No exterior leaks.
This also occurred with very similar symptoms with underground main journals and standard main bearings. Better pressure except when hot.
With no errant noises, it is likely something simple.
When I found oil gallery plugs missing, the pressure was low in a similar manner. The front main and front oil pressure tap were low on pressure. No exterior leaks.
This also occurred with very similar symptoms with underground main journals and standard main bearings. Better pressure except when hot.
With no errant noises, it is likely something simple.
Thanks, the fact that the you were seeing similar symptoms gives me hope.
04-08-2016, 10:48 PM
