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 What is too high oil pressure?
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ratty
V4 Fanatic

246 Posts

Posted - 02 Jan 2015 :  14:32:55 Show Profile Reply with Quote
We have had a new engine built up using a 1.7 crank and bought a Burtons Hi pressure oil pump suitable according to Burtons for V4 or V6. The problem is it is reading 100 psi from cold and 80 psi when warm. Surely this is too high? I bought the same pump for the other car and that runs 75 psi cold 55 to 60 hot. Any ideas anyone? we have ordered another pump from Burtons.

john-saab
Administrator

United Kingdom
2675 Posts

Posted - 02 Jan 2015 :  16:32:57 Show Profile Reply with Quote
I'm guessing that the psi will come down when the engine is run in a little. I remember Peter C stating that his original engine was running high oil pressure..not quite 100psi though.

'73 96 (Vernon),'74 95 (Veronica)plus 4 other 95's and 2 96's
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pchristy
V4 Guru

United Kingdom
1779 Posts

Posted - 02 Jan 2015 :  17:02:10 Show Profile Reply with Quote
Whilst Ford engines are usually low-pressure, if you've fitted a high pressure pump, I wouldn't be surprised to see 100psi - especially in the cold weather we've had recently!

My original (blue engine) V4 struggled to get over 40 psi under any circumstances, and when I got my current 96 (Vege engine), I was pleasantly surprised to see well over 50 psi in normal running. Starting from cold on a winter morning, I often see 80 psi until it warms up.

Bearing in mind this is a newly rebuilt engine, in a cold snap, with fresh oil, I wouldn't be surprised to see it that high - at least until it warms up a bit!

I seem to recall a couple of years back, one of our Scandinavian members posting a picture of his instrument panel, showing over something like 5 bar (70psi?) at tickover. I remember commenting on it at the time, and the reply being that he had a high pressure pump fitted.

If the engine is showing no signs of distress, I would guess its probably OK!

In any event, you'll soon find out!!! ;)



--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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Derek
V4 Guru

United Kingdom
1872 Posts

Posted - 03 Jan 2015 :  11:16:58 Show Profile Reply with Quote
Isn't the oil pressure regulated by the pressure relief valve on a new pump? The old trick was putting a washer under the spring can up the pressure. As the clearance between the pump gears and the face plate increases, the pressure reduces. Where does the pressure gauge get it's reading from on a V4? I think my old 1500 Cortina took the pressure from one of the cam bearings, low at about 45psi, as Pete says. This isn't much use when wondering what your big ends are getting.
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pchristy
V4 Guru

United Kingdom
1779 Posts

Posted - 03 Jan 2015 :  13:30:07 Show Profile Reply with Quote
The pressure take-off point for the oil light (and via a T-piece, the pressure gauge) is down by the petrol pump. I doubt if its being fed from the cam bearings - they're at the top of the block in the middle. Also, IIRC, the balance shaft is the last item in the oil pathway, and that is on the other side of the engine. So I would guess that the take-off point is somewhere fairly early in the path.

Derek is right that there is a pressure relief valve in the pump. Often the spring in this goes weak, and it opens too soon, hence the washer trick. However, this will only come into play if the pump can deliver enough pressure in the first place. Since Ratty has fitted a special pump, the normal rules won't apply! If it is a high-pressure type suitable for a V6, then it should have no problem delivering sufficient oil to a V4! It probably also has an uprated relief valve, but the only people who would really be able to answer that is the suppliers, Burtons.

Ratty notes that he has used a similar pump in the past, with more normal pressure readings, but it isn't clear if this was fitted to a freshly re-built engine or not. It could just be that the new engine is a bit "tight" and needs to settle in a bit......


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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TomS
Starting Member

United Kingdom
32 Posts

Posted - 03 Jan 2015 :  17:06:03 Show Profile Reply with Quote
One hundred PSI cold sounds very high, assuming the pump has the correct strength spring fitted it could be the valve sticking in the pump body. The big danger is blowing the oil filter o ring seal if you rev the engine up from a cold start.
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ianh
V4 Fanatic

United Kingdom
241 Posts

Posted - 03 Jan 2015 :  17:57:17 Show Profile Reply with Quote
High-pressure pumps can overwork the oil and cost power.
I fitted a standard pump to my 1700 engine build and found that when I primed the pump my electric drill was working very hard. It makes sense to change the drive shaft if you are going for the extra pressure. I seem to remember 10 psi per 1000 RPM as a rule of thumb.
I am getting 55 psi
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GeoffC
V4 Fanatic

United Kingdom
411 Posts

Posted - 03 Jan 2015 :  18:22:42 Show Profile Reply with Quote
When I built my rally engine I used a std pump with a sport & rally high pressure spring. Initially I got over 100 psi when cold and then it ran at about 75. After I ran the engine in (approx 500 miles) it settled at 80 to 90 psi cold and 65 to 70 when warm idling at 50 to 55 psi. So I would agree with Pete in that it's likely to settle down once run in. After several years of extreme use my engine was still idling at 40 psi and running around 60 to 70 psi with the stronger spring.
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ratty
V4 Fanatic

246 Posts

Posted - 03 Jan 2015 :  20:26:38 Show Profile Reply with Quote
Tomorrow the engine comes out for the third time! Sump off, main bearing caps off and check oil ways for obstructions or whatever just to double check. There has to be a reason. The pump in the other engine was new from Burton's,
so both the same, and was all new, crank reground, new shells etc. Just waiting for new pump to arrive.Will let you know the outcome.Both cars are entered for the Exeter trial this Friday 9th and 10th!
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Woody
V4 Guru

United Kingdom
2442 Posts

Posted - 03 Jan 2015 :  21:30:32 Show Profile Reply with Quote
My rally engine used to run 100 at start up and 70-80 when warm. It has settled a bit since the reassembly. Have to crank her up tomorrow and see.
Blowing oil out via crank seal did happen but that was down to crankcase pressurising and not the pump.
I wouldn't worry about it. Certainly not enough to pull the engine and strip. Just check you have good oil flow at the rockers and the oil is clean.
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ratty
V4 Fanatic

246 Posts

Posted - 03 Jan 2015 :  23:12:05 Show Profile Reply with Quote
Woody that is interesting. So far presuming your guage is accurate then you are using the highest pressure with no ill effects? perhaps we are worrying too much? Still can't get my head around the fact that we have rebuilt 2 engines , one 1.5 and 1.7 otherwise the same spec.and both using Burton's high pressure pumps, all new of course, different pressures in first post. Why? Pump faulty or blockage, misalignment, etc?
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mettersl
V4 Fan

United Kingdom
103 Posts

Posted - 04 Jan 2015 :  11:01:43 Show Profile Reply with Quote
You could always move to a modern thinner oil if you are worried...these engines are 20/50 originally aren't they? (mine hasn't run for 30 years so I forget) 10/40 is pretty standard in more modern engines and should lower the pressure a little but still protect all the parts.
Modern oils are more effective at preventing engine damage anyway.
In the end the aim of the oil pressure is to stop the bearings touching when the compression stokes fire (as well as providing oil flow over the other parts).
I'm not sure why higher oil pressure would be a benefit, but will take engine power to achieve.

Have a look here for more information.

http://www.classicinlines.com/OilPressure.asp

Lee

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Derek
V4 Guru

United Kingdom
1872 Posts

Posted - 04 Jan 2015 :  12:22:48 Show Profile Reply with Quote
Before doing anything I think I'd have a word with Burtons. Tell them about the different pressures with the same new pumps. They might agree to swap it but it would be worth stripping it down and checking all of the relevant clearances. It might be that all of the numbers measure at the very bottom of the range giving a very tight pump. Measure the spring. Burtons should be able to give you all of the numbers.
A wee bit off topic but if there is an option of a high capacity rather than a high pressure pump would a high capacity one be better with modern oils? What does a standard new pump produce 70/50 cold/hot? Isn't that enough? Lots I could speculate about here.......
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ratty
V4 Fanatic

246 Posts

Posted - 04 Jan 2015 :  18:55:29 Show Profile Reply with Quote
Sump off this morning. Main bearing caps off, everything was all lined up as should be.Plenty of oil everywhere.Pump removed to be stripped and checked a second time. However new pump should arrive tomorrow from Burton's and will be fitted. They don't specify what the oil pressures should be. I also can't get my head around that the pump is suitable for a v4 or a v6. Surely the pressure would be considerably different between the two? JDT and Simps. Any thoughts? Everyone else thanks for your observations and comments. A final conclusion and result will soon be! Will let you know the outcome.
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mettersl
V4 Fan

United Kingdom
103 Posts

Posted - 04 Jan 2015 :  19:48:26 Show Profile Reply with Quote
I have a v6 pump, in its box...bought in the 80's from Ford for the 2.8 l cologne engine, its about 25% bigger in diameter than the V4 pump. I was trying to save money as it was about half the cost of a Saab reconditioning kit, let alone a new pump and ford UK wouldn't supply cologne V4 parts. I didn't fit it in the end as it would have meant enlarging the sump, bashing it out didn't give enough clearance. I fitted a SAAB reconditioning kit to the original, but have since wondered if I should put a new pump in...my standards have risen quite a bit since I was 18 and did the work. The engine has yet to run...30 plus years later, sealed and kept inside, it still turns over easily.
The pressure is set by the relief valve spring pressure, a high pressure pump has a stronger spring.
Capacity is set by the size of the pump. Putting a bigger capacity pump onto the engine will mean more oil out of the bypass, but not necessarily more pressure. The pressure will in any case be set by the engine condition, smaller clearances of blocked oil ways will mean higher pressure. 10psi per 1000 engine revs needed is apparently the maxim...so 50-60psi max should do us. Higher pressure than needed uses more power.
I did study all this when I trained as an engineer, but 30 years in commercial jobs means I am a bit rusty.
There is a lot on the web about this topic if you Google it.

Lee
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Woody
V4 Guru

United Kingdom
2442 Posts

Posted - 04 Jan 2015 :  23:23:41 Show Profile Reply with Quote
Fired the Troll up this morning, it was absolutely freezing, and took a while to get the engine going, as I hadnt run it for 6 weeks or more. Last outing was to the last Limes Cafe meet for UKSaabs in November. Pic below of oil gauge at start up. Didnt have time to run up to full temp to get hot reading. Will try another time.

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