How much is too much? - Oil pressure

73 Mike

I'll drive it someday
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I posted a while ago that the oil pressure in my cheepo crate engine 350 runs extremely high. Idle pressure was on the order of 100 PSI and it was higher at speed. I attributed part of the issue to running high viscosity oil (15W40 Rotella) and part to running a filter mount without a bypass. I also have an HV oil pump on there which was necessitated by the oil pickup being welded on to the pump and this was the only pickup that I had that fit the pan.

I'll say up front that I know nothing about the engine other than it runs pretty well and is very gutless.

Over the weekend, I changed the oil for the first time since I put the engine in. There wasn't much mileage on the oil but there was a fair bit of time. Besides, I keep expecting the oil pressure gauge line to pop off and flood my compartment so wanted to solve the issue.

First off, I found a normal, bypass oil filter mount. Only tested it by pushing on the valve and having it give but is seems to be working correctly. Guess my memory isn't what it once was. Could be that it never was and I don't remember.
:confused2:
Second, I put in 5 quarts of 10W30. Started it up and immediately pegged the oil pressure gauge. I've not put more than a couple of miles on it since and the pressure does occasionally drop below "pegged" but it's still pretty high. I've not put a calibrated gauge on it, nor do I intend to.

The question is, besides robbing power from an already anemic engine and the possibility of a cockpit oil bath, is there any other potential harm to the engine?
 
Seen engine peg 80 and then settle down after a while and miles.....

but that does seem like a plug/obstruction in the oiling....did you pull the valve covers and see what?? run that thing and see the valve oiling??

how about the stethescope probe on the engine block, anyone not happy??

wonder is the gauge is correct....buy a China cheepie and screw it home to see....

you say anemic, some engines are so tight they squeek....how's the temp??

:ill::drink:
 
Runs hot. Not insanely so but hot.

Tons of oil in the heads. Spewed it everywhere when priming but that's another story.

I did check the pressure with a set of Mac gauges at the back of the block. Definately high

http://www.vettemod.com/forum/showthread.php?t=6136

I'm fairly sure that I have a gear cam drive in there and it's pretty noisey. Between that and the side pipes, pretty hard to hear anything else.
 
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Runs hot. Not insanely so but hot.

Tons of oil in the heads. Spewed it everywhere when priming but that's another story.

I did check the pressure with a set of Mac gauges at the back of the block. Definately high

http://www.vettemod.com/forum/showthread.php?t=6136

I'm fairly sure that I have a gear cam drive in there and it's pretty noisey. Between that and the side pipes, pretty hard to hear anything else.

I no expert, but so it seems if you have good oil flying all over the fenders with VC's off it seems the lower end should be happy....but you need a stethescope with probe to tell, put on near the drain plugs on bottom end....

that probe will tell the tale, if everyone is happy you hear a whirring sound, if NOT...you hear a fugly knocking sound....do that first, before any other action...IMO...

summfin ain't right, I bet on instrumentation....

:gurney::drink:
 
Really about all there is to it was in your other thread.
I think the old 427 ford side oiler was set a t 125psi, but I don't know what bearing clearances it used.
The possibilites are, relief valve inoperative or spring too strong, bearing clearances too tight, too much oil flow (hv pump). No matter what, you should be running max at the relief valve setting, which should be 70psi.
If your just cruising around locally, I wouldn't worry too much, extended drives I might just because of temps. Just watch the temps and maybe switch to a thinner synthetic.

If your really concerned, then drop the pan, check a couple bearings and install a standard pump but check the relief valve spring.
 
If your really concerned, then drop the pan, check a couple bearings and install a standard pump but check the relief valve spring.

I guess I'm on the fence. This is essentially a throw away engine that I got very cheap to tide me over until my next one is ready. Having said this I'd rather it not go up in a ball of flame in the middle of a drive. :lol:

I think I've kind of run the course for now as far as effort is concerned. I'm going to try taking a stethoscope to it on Saturday to see if there is anything obvious though I'm not sure what I'll do if I find it.

I also think you've hit right on the head the thing that concerns me the most. If the engine were to turn to slag while I'm driving around the block, a quick call to triple A solves the problem. It would be an incentive to get the new engine done. I am, however, thinking about a cruise that would be a few hundred miles round trip. If the issue is bearings or something equally critical, I imagine that it will show itself at the least opportune time.
 
with the relief spring you should not see pressure higher than 70psi. I run a Melling HV pump as well and it's 70psi at idle when the oil is cold, 40-50psi when cruising with hot oil.
If you're sure the gauge reads correctly then I'd check the pump and relief spring... heck, a stock pump is only $20, might as well just swap it and be done with it....
 
I read the part about a throw-away engine. There's no point in killing it. Drop the pan and oil pump, check the relief valve. I'd bet it's stuck. That much load on the oil pump drive, it's going to wear the bottom bushing in the distributor and load the cam gear too. Ask Bird about my TI dizzy- all it ever ran was the GM ZL-1 pump and the lower bushing and shaft are DONE!
 
I read the part about a throw-away engine. There's no point in killing it. Drop the pan and oil pump, check the relief valve. I'd bet it's stuck. That much load on the oil pump drive, it's going to wear the bottom bushing in the distributor and load the cam gear too. Ask Bird about my TI dizzy- all it ever ran was the GM ZL-1 pump and the lower bushing and shaft are DONE!

Yep, and double yep.:blush:
 
I read the part about a throw-away engine. There's no point in killing it.

Not trying to kill it at all. I just don't want to get too caught up in trying to sort out a problem like this. At the very least I'll replace the relief valve this weekend and see if that sorts it out.
 
I'm home with a cold today so I have a chance to stop and think for a change. I've also had a little free time to read.

Something that has bothered me all along is that I've never seen how the filter bypass relief valve would lower the oil pressure at the gauge end of the system. After all, there is only one input hole and one output hole.

I now realize that we have been talking about two different bypasses. Because I thought that I was running a filter adapter without a bypass, that's the one that I thought that you were refering to. I now realize that you all were talking about the bypass and spring on the oil pump. Do I have it right now? Rereading Tim's post struck me as odd until I thought about it further.

Sorry for being so slow on the uptake.
 
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You say you know nothing about the engine... who built it and who installed the oil pump ?? I'm asking because from what you're saying about mixing up the two bypasses .... is it possible that whoever built the engine plugged the pump bypass instead of the filter mount bypass ???? That would be bad.... at that high pressure from the pump I would think the filter mount bypass would always be open and your oil would never go thru the filter..... :shocking:
 
I certainly don't know anything about the engine but I'm pretty sure that the oil filter bypass isn't stuck open. I never checked it's function but the plug does move freely and springs back when I pressed my finger in it.
 
I'm not saying the oil filter bypass is stuck. If (and that's IF) somebody plugged the pump bypass then the pressure and flow provided by the pump is so high that it will open the filter bypass...

Like I said earlier, the pump bypass normally limits the pressure to 70psi or so..... unless the gauge reads incorrectly you should never see >100psi in the system......
 
I hear what you're saying. I'm probably just going to replace the pump and intake. It isn't expensive and if I'm going through the trouble of pulling the pan, I 'might as well make sure. WHen I do, I'll pull appart the old pump and bypass and see what I can see.
 
Looks like you had an "AH_HA" moment.

Yep the filter bypass and the pump bypass are different. The filter bypass opens to bypass the filter is the oil is too cold to go thru it or the filter plugs up. (kind of the same thing). The pump bypass/pressure regulator is a little piston and spring in the pump itself. When the pressure gets to a determined point, that overcomes the spring and opens a port that dumps oil back to the pan.
I've seen guys weld/braze the pickup into the pump (GOOD IDEA!) and not remove the spring (BAD PLAN!). The heat takes all the spring out of the spring (got that?) and depending on how much of the bypass port is covered, that becomes the new oil pressure limit.
The whole bypass thing in the pump is just held in there with a roll pin. Look at the pump and you can see it.

Just for grins, figure that even if the whole engine was built to the low end of the factory clearances (like that will ever happen), there's going to be enough oil pressure to keep it at the high end of the specs- which still is not much over 65psi
 
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Just to close out this thread, I changed out the oil pump and pan a couple of weeks back. I still used a high volume pump (because I had one) but used the lightest spring for the bypass. Pressure is still around 60 at idle and 75 PSI at speed but at least it's reasonable. I used 15W40 because I needed almost 8 quarts (7 qt pan) and didn't want to spend a fortune on oil and additive before making sure that the pan didn't leak :eek: I'll probably try 5W30.

I pulled the pump apart yesterday and everything looked to be in good working order including the bypass piston. Looks like the issue was no more than a stiff spring.
 
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