engine and drivetrain New Engine Rebuild Oil Pressure Problems

[felix_666]

Interesting.  100+ psi at idle cold?  I've only built 4 or 5 motors, but with the new generation pumps, I've never seen that.

 

See if we can get Byron to chime in here, he's built more motors than I've eaten croissants...

 

Given, I guess, that it's usually not that cold here, and we don't race in the winter.

But I DO dd my car, even when it's well below freezing.

 

Now, the cars with stuck valves, those peg 150psi gauges at 2500 when they're not warm.  And I've had a few of those, too.

 

But to your filter problem, I've had it too, and ONLY on cars where the relief's not working.  Not sure why yours isn't,

but given what you've tried with filters, I'd be willing to bet a rusty trunk lid that it's not.

 

what I think,

t

 

okey doke.

 

lets say for a minute that it is the relief valve getting stuck, once my car warmed up the pressure dropped to 40-50psi, at this point I'm guessing it not stuck, right? 

 

So if it becomes unstuck after it warms up, whats making it stick (resisting 120+psi) for the initial period? Given I pulled it apart and everything looks fine, is there maybe an initial bedding in period??

 

 

My uneducated guess as to how the relief valve works, is as the pressure builds, the piston is pushed back against the spring and allows oil to bypass the system and be dumped back in the sump, with greater pressure resulting in more oil being dumped, obviously there are limits. Is this correct? Just so O'm clear. 

Edited July 24, 2013 by felix_666

[jgerock]

Interesting thread. Sorry you are having troubles with your freshly rebuilt engine.  Looking at the picture of your oil pump, is it possible the shim was installed backwards so that the clearance hole for the relief port was blocked?

[felix_666]

Interesting thread. Sorry you are having troubles with your freshly rebuilt engine.  Looking at the picture of your oil pump, is it possible the shim was installed backwards so that the clearance hole for the relief port was blocked?

 

 

 

Wouldn't this mean that the pressure would remain high (100+psi) the entire time, instead of dropping like it has?

[FB73tii]

Have you tried swapping in a different (used, known to be good) oil pump? That will resolve whether the issue is in the pump or elsewhere. I hate those little plungers, they can be tricky. Also, pull the plunger out of the new pump and look down the plunger bore with a good light. A new pump I bought recently (past few years) was poorly cast and there were air bubble holes in the bore, exposed when the bore was cut. That pump worked fine, but you need to look at all friction surfaces.

 

Keep us posted! --Fred

[felix_666]

Haven't swapped the pump. Was hoping that would be a last resort.

When I pulled the pan last week I disassembled the relief valve, plunger and all, stuck a light on the bore, gave it a light wet sand, lubed it all and put it back together.

[FB73tii]

I wet sand not so much to smooth the piston (generally smooth when new) but to reduce the diameter ever so slightly. Since you started with 600 grit you really have not removed much material. I think one time I wrapped 400 grit around a pencil and wet-sanded the bore a bit as well. Certainly is a pain to keep pulling the pan and pump. Is your pan baffled? (I know you are running a scraper, but that should not interefere with pulling the pan.) My pans are baffled and will not come out easily. I drop the subframe a bit, reach in and unbolt the pump, then pull the pan and pump out together. Reverse procedure for install. I will be glad to install my dry sump engine later this year, no more pesky stock pump!

 

--Fred

[felix_666]

Is your pan baffled? (I know you are running a scraper, but that should not interefere with pulling the pan.) My pans are baffled and will not come out easily. I drop the subframe a bit, reach in and unbolt the pump, then pull the pan and pump out together. Reverse procedure for install. I will be glad to install my dry sump engine later this year, no more pesky stock pump!

 

--Fred

 

Pan is baffled, no scraper. Is a serious pain to pull the pan with the baffle, I got ahead of myself when I bought all the engine parts, regretting the baffle now.

 

I was a little nervous of sanding the piston too much, I guess now a little more couldn't have hurt, bummer.

[FB73tii]

Don't regret the baffle, a very good thing if your are driving the car on track (or similar ). Got to keep that oil under control, don't want the oil pump to suck air under heavy braking or side load and eat the bearings!  --Fred

[TobyB]

40- 50 psi at idle is also 'pretty' high, for warm...

 

...but here's the real question- once it's fully warm, what happens when you tach it up to, say 4k?

In my experience, pressure should rise to the full relief point (60, 65, 70 depending on the engine,

oil, relief system, etc) and then stay there.  Usually it gets there by 2000, and then only climbs maybe

5 lbs to redline.

 

Oh, sorry- when I say fully warm, I'm talking about oil temps, not water temps.  I forgot, if you're idling

it in a cool shop, the oil temp will stay pretty low, and pressures will be high.

 

As to a sticking plunger, every one I've had (4 or 5 now, on one engine I built new and several used and parts motors)

does this:

It sticks closed when cold.  You get a TON of oil pressure at start- up, and even on a used motor, revving it

above 3500 WILL blow the filter off if it's really cold.  I drive them to a max of 2500 rpm for a few minutes.

As the oil warms up, the pressures drop some.  

At a certain point, the pump housing warms up enough that the plunger unsticks itself, and the thing behaves normally,

with a maximum of about 60 psi, and idle pressures of 20 to 30 psi, depending on engine, temp, oil, etc.

It behaves while it's still warm and sometimes for the rest of the day.

It cools off overnight, then, the next morning, it's stuck shut again.

 

My take is that the aluminum housing expands a lot faster than the steel piston, and clearances open up as it

warms up.  

 

Hope this helps-  it's certainly odd that it's doing this.

 

t

[felix_666]

Update: last time I started the engine I fitted a oil gauge and pegged 300_psi on start up which dropped to about 50psi once things had wasrmed up. After another start the oil filter seal burst again. I'm going to pull the sumo again (arhhhhhhhh) and sand the piston a little more and chech the o-rings are in place. I can't hack the engine spewing oil every fee times I start the engine. Its too degrading.

I'm currently in central america on holiday and will sort it out when I return home. Currently about to motorcycle around some volcanoes in Guatamala... Woo

[ndog]

so what is the right oil pressure on cold start with 10w30,10w/40.10w/50

under normal usa ambeint temps?

i have the blue books and many other books but it seems like each engine is different at 40plus years old.

Edited January 7, 2014 by ndog

[allbim]

I am very paranoid about the oil filter seal blowing. To prevent that from happening I installed a hose clamp over the gap between the filter and the filter housing. I hope that will keep the o-ring from blowing all the way out and slow down the leak enough to give me time to figure out what's going on.

That said, as jgerock asked, is it possible that you installed the shim the wrong way? Not having an engine and pump in front of me, I'm not sure that can be done.

Edit: Hmmmm, I just realised how old this thread is. I hope the problem is sorted out by now. An update would be nice so that we can all learn from it.

Edited January 7, 2014 by allbim

[felix_666]

I am very paranoid about the oil filter seal blowing. To prevent that from happening I installed a hose clamp over the gap between the filter and the filter housing. I hope that will keep the o-ring from blowing all the way out and slow down the leak enough to give me time to figure out what's going on.That said, as jgerock asked, is it possible that you installed the shim the wrong way? Not having an engine and pump in front of me, I'm not sure that can be done.Edit: Hmmmm, I just realised how old this thread is. I hope the problem is sorted out by now. An update would be nice so that we can all learn from it.

I'm overseas, haven't sorted the probnlem.

If I can get the engine to warm up without blowing the seal, the pressure drops to about 50psi.

If I had installed something incorrectly, such as the shims, I don't think the pressure would ever change, it would surely remain much higher like I've reported in previous posts.

[allbim]

No matter what is wrong, the pressure would still change as the oil warms up, because the viscosity changes with temperature. However, if the bypassed oil were totally blocked (i.e no bypass), I believe the pressure would would be higher than 50 PSI above idle speed even when hot.  

Edited January 9, 2014 by allbim

[felix_666]

Problem solved....

 

 

...well sort of.

 

The needle valve gives me the ability to get the engine running properly, tuned the carbs and timed it. Now runs like a dream.

 

Once warm the pressure drops to around 30psi and the needle valve is closed. This is first time I've properly been able to play with the throttle and get the engine working a little, trying to seat things.

 

Not conventional, but whilst I still have some high spots in the engine this is my solution..... deal with it.