Oil Pressure Problem

[Scotty]

I have an issue where the Oil Pressure has been running at 40 reliably (according to my very original oil gauge). I adjusted the Weber because it's still running too rich and it dropped like a rock to 25 and is staying firmly there unless I accelerate.

When I start the car I have to press the gas for it to start otherwise it's not getting enough gas at the carb. Once it starts, it runs and idles. The engine doesn't sound right but isn't making knocking noises or anything strange, it just sounds starved.

What I know:

• Rebuilt engine with ~30 mikes on the clock.
• Rebuild was done right by a known professional.
• Running 15-40w Oil.
• 1725cc Weber 32/36 that was running rich and refuses to so far behave
• Checked dipstick. All oil, all day. No gas smell.

I haven't driven it for a few weeks and when I did it ran reliably with no issues. This time I had to shut down because the temp gauge kept climbing and I shut it down right before it puked up a little bit of coolant. I ran a radiator check to make sure the Head Gasket wasn't blown and it came back negative.

What should I be looking for, what could I be doing wrong and how do I fix this?

As always, muchas gracias in advance!

 

[RootesRooter]

Was it really 40 psi all the time? 25 at idle is 'good normal.' 40psi requires roughly 2000 rpms at a minimum.

I'd start by reversing the adjustment you made to the Weber.

 

[alpine_64]

The only impact the carb could have on oil psi is if

1. its running very rich it could dilute the pil.. You say that's not happening.

2. The carb is runnig very lean and making the motor run hot... Giving the oil a hard time.
You say the car is puking coolant... Did you adjust the carb leaner to compensate for your rich moxture?

You could test the oil psi with a remote gauge from the block.

 

[hartmandm]

Series V with the brass oil pressure relief valve?

What oil pressure are you seeing just after starting when the engine is cold?
What oil pressure are you seeing shortly after starting when the engine drops to the usual idle speed (at or less than 1k rpms)?
What oil pressure are you seeing when the engine is normal temperature (85C) at idle?
What oil pressure are you seeing when the engine is normal temperature at 2k rpms or greater?

Mike

 

[Tim R]

Scotty,
I wonder if your adjustment of the carb when this problem started is just coincidence.
Could the PRV be being held slightly open as shown in this video? It is easy to whip it out and clean it.

Tim R

 

[Gordon Holsinger]

I have an issue where the Oil Pressure has been running at 40 reliably (according to my very original oil gauge). I adjusted the Weber because it's still running too rich and it dropped like a rock to 25 and is staying firmly there unless I accelerate.

When I start the car I have to press the gas for it to start otherwise it's not getting enough gas at the carb. Once it starts, it runs and idles. The engine doesn't sound right but isn't making knocking noises or anything strange, it just sounds starved.

What I know:

• Rebuilt engine with ~30 mikes on the clock.
• Rebuild was done right by a known professional.
• Running 15-40w Oil.
• 1725cc Weber 32/36 that was running rich and refuses to so far behave
• Checked dipstick. All oil, all day. No gas smell.

I haven't driven it for a few weeks and when I did it ran reliably with no issues. This time I had to shut down because the temp gauge kept climbing and I shut it down right before it puked up a little bit of coolant. I ran a radiator check to make sure the Head Gasket wasn't blown and it came back negative.

What should I be looking for, what could I be doing wrong and how do I fix this?

As always, muchas gracias in advance!

 

[Gordon Holsinger]

I got a new relief valve Alpine Tiger spares in the UK.

 

[Scotty]

Scotty,
I wonder if your adjustment of the carb when this problem started is just coincidence.
Could the PRV be being held slightly open as shown in this video? It is easy to whip it out and clean it.

Tim R

Where is the PRV located on a 1725 engine? I don't want to unbolt something that isn't it. The car has sat so I can see this as being a possible.

I did adjust the mixture yesterday so it's a lot leaner so that's probably causing my heat issue, I'll wind it back today. Going to do some work today on the car and I'll answer everyone's posts. Thanks so much all for helping me on this, it seems to be a never-ending series of issues of upkeep on this car but that's ok - only way I'll learn how to take care of it!

 

[Gordon Holsinger]

Where is the PRV located on a 1725 engine? I don't want to unbolt something that isn't it. The car has sat so I can see this as being a possible.

I did adjust the mixture yesterday so it's a lot leaner so that's probably causing my heat issue, I'll wind it back today. Going to do some work today on the car and I'll answer everyone's posts. Thanks so much all for helping me on this, it seems to be a never-ending series of issues of upkeep on this car but that's ok - only way I'll learn how to take care of it!

 

[Gordon Holsinger]

Where is the PRV located on a 1725 engine? I don't want to unbolt something that isn't it. The car has sat so I can see this as being a possible.

I did adjust the mixture yesterday so it's a lot leaner so that's probably causing my heat issue, I'll wind it back today. Going to do some work today on the car and I'll answer everyone's posts. Thanks so much all for helping me on this, it seems to be a never-ending series of issues of upkeep on this car but that's ok - only way I'll learn how to take care of it!

On the oil filter block that the filter goes on there are two 7/8 hex heads I think it is the one at the front you unscrew and the valve comes out. There are two types of valves one is an early type and a later type check past posts for photos of the two types later valves can be found at Alpine Tiger spares in the UK.

 

[hartmandm]

The OPRV is on the side of the oil filter block.





Steel version:


Brass version:


Mike

 

[Tim R]

Scotty,
That was why I sent the link to the video, it shows where the PRV is located. At one point in the video it shows a PRV that we had that wedged itself partially open and led to the symptoms that you describe. Hopefully you will be able to fix this without too much trouble.


Tim R

 

[RootesRooter]

Before you start unbolting everything, please start your Alpine and answer Hartmandm's questions above.

In addition to his questions, I would add: Take your Alpine out for an extended drive (1/2 hour or more) on a highway where you can keep your rpm's above 3000. Note the initial hot oil pressure at speed. At any point does the pressure slowly (over a few minutes) drop while maintaining those rpm's?

The answers to those questions should tell you if your PRV is cause for concern.

 

[RootesRooter]

I've got a problem with the above video. None of the psi's they describe or show match up to the specs of the PRV's initially used in Series V's. (Were different PRV's used in UK SV's?) Per the manual, the SV PRV was rated at 45 hot, not 55. In 40+ years I've never seen a fresh 1725 turn over 30 psi at hot idle, far from the 40 psi they quote and show in the video at the 1:51 mark. If they want to swap in the pre-SV PRV with its much higher 55 psi rating, fine, but please label it as such.

 

[Scotty]

Was it really 40 psi all the time? 25 at idle is 'good normal.' 40psi requires roughly 2000 rpms at a minimum.

I'd start by reversing the adjustment you made to the Weber.

I'm sorry I'm running late with responses, I have a procedure today for my hand and haven't had a chance to really do anything with my Alpine. I am going to wind back the Weber and set it how it was.

So it's perfectly clear, according to my Oil Gauge, which I have said might be inaccurate since it's 60 years old my SIV 1725 has always started stone-cold and sat at 40 PSI @ 9-1000 RPM and when I drive it generally stays that way when I drive out. I don't notice the gauge jumping or dropping.

The last time I ran it, it dropped from 40 to 25. I shut it down, let it cool (20 mins) and when when I started it again, it did a slow climb from 0 to 25 so I've been thinking maybe it's the gauge itself. The engine is running hot but that's probably due to me having it running far too lean, like it has been mentioned.

Saying THAT, I mainly drive the car at night and when I'm driving I mainly pay attention to the Temp Gauge which has been redone and checked with a thermogun and is now quite reliable. I'll drive it again during the day and pay close attention to the Oil Gauge.

 

[Tim R]

RootesRooter,

Any errors in the pressures quoted are 100% down to me as I made that video. I was unaware that the standard oil pressure was reduced for the 1725 and should have labelled it as such and apologise for this error. The figures quoted were from an earlier workshop manual.

We have run 1725s to the pressures quoted in the video since about 1983 when we made our first adjustable PRV. Setting the engine to the higher pressure will certainly not do it any harm and is something that I would recommend to anyone. An adjustable PRV lets you fine tune the oil pressure according to the grade of oil and state of the engine.

In 'Tiger' Tom Ehrhart's 1985 article on low oil pressure he talks of increasing oil pressure from the standard 40-45lbs when hot (presumably he is referring to 1725s) to the 50-70 lbs range and states that "pressure in this region will do nothing but enhance engine durability for street driven engines and is absolutely mandatory for race engines". He suggests that more than 90lbs when cold is too much and warrants a change to thinner oil!

Best Wishes,

Tim R

 

[RootesRooter]

Tim R,

Thanks for the explanation. I appreciate your effort making these videos. I don't know who made the recent video showing how to resolve excessive play in the steering column, but its probably going to save me a whole lot of time and aggravation this spring.

I understand the rationale and utility for the adjustable PRV's, but I hafta tell you, if I were looking at an Alpine for sale and I saw one of those bolts sticking out of the PRV, I'd walk away.

For all the sticking problems with the early SV PRV, overall the PRV's read pretty consistently. If I see a stock SV that's reading, say, 35 psi warm, at speed, I've got a solid clue as to how worn the engine is.

But once that adjustable screw is turned, you can't go back with any certainty. The stock reference point is lost for good.

 

[alpine_64]

But once that adjustable screw is turned, you can't go back with any certainty. The stock reference point is lost for good.

Making an adjustable oprv is not a bad thing installed on a fresh rebuilt spec motor...
The real worry is when people use an adjustable oprv to bring psi " back to spec" the reason oil psi drops off is the clearances in the beafinga or the pil pump have got to large. Masking it by adjusting the valve hides the issue and lets it get worse.... Its like saying jist increase the revs to bring the psi back up....

 

[Tim R]

RootesRooter and Alpine_64 the points that both of you make are 100% correct but increasing the oil pressure benefits any Rootes engine whether it is worn or not. We fit adjustable PRVs and increase the oil pressure on all of our engines including when they are first rebuilt and everything is as tight and as good as it is ever going to be.
This morning I took my own Alpine out, it is cold here at the moment and the oil (20/50) was thick. At start up the engine showed 6o+ lbs pressure at tick-over. When I got back from a run and everything was hot, it was showing a steady 40lbs at tick-over. (around 750 rpm) With the pressure at this level the oil pump is not over strained but you are getting a really good supply all through the system.

Scotty's pressure is dropping to 25lbs, that suggests a problem somewhere and a sticky PRV would seem to be a likely culprit.

Best Wishes,

Tim R

 

[Mike O'D]

RootesRooter - if you back the screw off, then it is the same as an un-modified PRV. Yes, low pressure will occur from increased clearances from wear, but also from a weakened PRV spring. The PRV allows oil to go from the pump directly back to the oil pan if the pressure is too high so it doesn't damage the pump. I see no downside to increasing low oil pressure back up into the normal range from whatever cause. Better that the oil pumps into the vital engine components rather than right back to the oil pan. My thoughts anyway.