Alfa Romeo Forums banner

1 - 20 of 25 Posts

·
Registered
Joined
·
208 Posts
Discussion Starter #1
Hello to all,

1985 spider Veloce

What is the optimum oil pressure and should if change from idle to driving normal speeds?


thanks
dmmarland
 

·
1966-2013
Joined
·
13,741 Posts
Yes it should change between idle and running speed. It should also change a bit between a cold engine and a hot one.

Somewhere in the vicinty of 75psi hot at speed, down to 7-14psi hot at idle.

Cold pressures will be a bit higher.
 

·
Registered
Joined
·
271 Posts
75 PSI? HOT?! I have never experienced pressure that high, let alone hot at high speed in any of my Alfas. Both current cars start out high when cold (Super at around 60, Spider 50) and settle down from there. Sometimes it's scary low when warmed up, esp in the Super's 1750. But I have learned, mostly from the fine folks here on the BB, that it's normal. I use Castrol 20W50 in both cars as well.
 

·
1966-2013
Joined
·
13,741 Posts
No fits of dyslexia. Mabe you guys just have loose engines ;)

From the 2L engine book on 15/50 weight oil:

Engine oil pressure, warm @ 800-900rpm 7.1 - 14.2 psi
Engine oil pressure, warm @ 5000rpm 49.8 - 71.1 psi
 

·
Registered
Joined
·
99 Posts
No fits of dyslexia. Mabe you guys just have loose engines ;)

From the 2L engine book on 15/50 weight oil:

Engine oil pressure, warm @ 800-900rpm 7.1 - 14.2 psi
Engine oil pressure, warm @ 5000rpm 49.8 - 71.1 psi
I agree my engine is nice and tight with 65K miles and no burning of oil between 2500 mile oil changes. I use 20/50 weight oil and when warn it runs at about 50 psi and then at about 75 psi at speed.
 

·
Registered
Joined
·
7,166 Posts
I wouldn't bet my life with the accuracy of the oil pressure gauge. To 80mph yesterday at 90 degrees outside temp., and running my winter oil 15w-40 I had about 40 lbs. It's now time to replace with 20w-50 but it still ain't going over 50 psi at 4K revs from past experience. Pressure is one thing but volume is another. I guess I could run straight 60 wt and get 70 psi but I don't thing the engine would like it:)
 

·
1966-2013
Joined
·
13,741 Posts
If it ain't barfing seals, it ain't hurting nuthin. :D (of course if the oil filter is crap and letting things get by, then there's a chance of things acting like an abrasive fluid cutter, but that's a maintenance thing, not a pressure thing.....)

For myself, I've been through three gauges and two senders in various combinations with each other over and over and they all came up close enough to each other where I'm not going to bother trying again. (no, I'm not going to hook up a mechanical gauge just to see, thank you very much :) )


Still, I'm sure folks have seen the deal with lapping the base of the pump gears and housing to get a nice close tolerance as it should be rather than what it ends up as during manufacture.

Or are people mistakenly thinking thier new pumps are perfect right off the shelf?
 

·
Registered
Joined
·
9,977 Posts
My ('74) owners manual says:

IDLE - min 7 psi
ENGINE RUNNING FAST - min 50 psi, max 65-70 psi

On the 70s cars there is an low oil pressure warning light that is set to illuminate at 5 psi. The manual says "No trouble exists if the warning light comes on while the engine is idling, especially when hot."

I don't have a Series 3 owners manual, but my guess is that it says the same thing.

Bottom line, IMHO, is that in a mid-service life engine you should see hot oil pressure above 5 psi (warning light extinguished) at Idle and about 50 psi above 2000 rpm or so. As the engine gets towards overhaul, you'll see that 50 psi value perhaps drop a bit. 50 psi is pretty high compared to the spec of many engines. I feel that you'll have little problem with oil pressures as low as 30 or so at hot running.
 

·
Registered
Joined
·
7,166 Posts
Bottom line, IMHO, is that in a mid-service life engine you should see hot oil pressure above 5 psi (warning light extinguished) at Idle and about 50 psi above 2000 rpm or so. As the engine gets towards overhaul, you'll see that 50 psi value perhaps drop a bit. 50 psi is pretty high compared to the spec of many engines. I feel that you'll have little problem with oil pressures as low as 30 or so at hot running.
. The only time my OP light comes on is on is when ignition on, before start up. Start up, the light goes out. Light has never come on at idle on a hot engine even using 15w-40.
 

·
Registered
Joined
·
1,051 Posts
I believe the numbers stated are a range.

Don't get excited or ready to rebuild because your engine oil pressure never gets to 75 psi. Too high oil pressure is as bad as running too low on oil. If you think the aluminum engine leaks a lot of oil, try running with oil pressure too high. At 4000 rpm running down the highway, all I care about is that the oil pressure is about 65 psi, and it ain't all the way to the left when idling.

People seem to get hung-up on the minor stuff like platinum vs. NGK plugs, oil filter brand, pain train for the little bud, all that garbage.

What matters is the maintenance and how often you perform it. You can have the best parts in the world on the car, but if you don't maintain the car, it won't matter after some time.

Enjoy the car! Drive it hard, and poke under the hood often.
 

·
Registered
Joined
·
438 Posts
from my observation I had S4 spider and now 69. I can tell that newer spiders S4 running lower oil pressure than older spiders.
 

·
Registered
Joined
·
125 Posts
Newbe here. Have 1973 Euro GTV. Engine was re-done 2 years ago. Driving yesterday Oil pressure warning light came on intermittently then stayed on. Oil pressure gauge was reading 40-60. Oil mid- level on dipstick and 20-50 is being used.
Thought? New Oil pressure sender?

Thanks
Perry
 

·
Premium Member
Joined
·
13,457 Posts
It could be a short to ground in the oil pressure switch circuit. I would check that before I started messing with the sensors. Disconnect the wire from the switch and see if the light still comes on. The switch is on the exhaust side of the block.
 

·
Registered
Joined
·
820 Posts
10 psi per 1000 rpm is about right and if you run the factory recommended viscosities at the factory recommended temps then thats what you will see. too much pressure just uses power , makes excess temps and aerates the oil. the oil pressure relief valve just is set at 65 i think and cold with correct oil thats what you will see. if you are seeing 75 with 220 degree oil of factory spec , then you are doing nothing more than make oil temp thru cavitation and using power. if its a rebuilt motor then the bearing clearences will define the oil you need . the temps never change. less that 200 degrees is bad for the motor and more than 260 is bad for the motor. correct is 210 to 230 and that will give you correct pressures at correct revs.

all you need is what you need. too much and too little are each wrong and bad for the motor in various ways.
 

·
Super Moderator
Joined
·
11,377 Posts
Slight change of subject. I build oil pumps for many many BB members all around the world, street performance or race, 750 101, 1300 &1600, all 1750's and race 2L's. I've been building pumps since the time I spent at AUSCA in the mid 60's.
It ALL has to do with where the pressure is measured. Generally, the pumps I build will deliver 100 # AT THE PUMP. The relief valve spring is calibrated, and will lower volume as pressure increases (to decrease pressure to design levels). With a fresh street engine, with good cam bearings, you should have about 70# at the rear main, hot 20-50 mineral oil, NO MORE. Race engines with more liberal bearing clearances will run a bit less. Engines with wear, mains or cam bearings, less still. Generally a 55# maximum at the rear main won't hurt anything, as long as the pump is adequite to maintain volume and pressure hot at idle of 3-5#.
Over time Alfa measured pressure in different locations with different type gauges some electronic with "dampers" so the needle wouldnt jump around. This type gauge will be slow to rise and drop. The only SURE WAY to know what pressure you have is with a mechanical gauge mounted somewhere (filter) near the pump main feed to the block.
Pressure AND volume work together. A loose engine with a good pump thast will deliver volume will show good pressure about anywhere. A pump with a tired relief valve spring that has taken a set and shortened the typical 3 mm will deliver poor volume, and shimming the spring will throw off it's calibration (like a weight scale spring) so it may read other than is needed at low, high or intermediate speeds.
So, if in doubt, measure pressure with an accurate mechanical gauge, as close to the pump as possible, and record readings with 20-50 oil hot at various speeds, comparing these values to whatever the dash gauge might indicate. A pump that is fresh and can deliver 100# at the pump, WILL deliver 70# at the rear main bearing if the engine is in reasonable repair.
I hope this helps. reading this thread it seems clear that everyone is not talking about the same observatiuons.
 

·
Registered
Joined
·
14 Posts
My ‘87 and ‘74 have both had upper end rebuilds in the last 5k miles. The spread on gauge oil pressure is about 18 psi between them with the ‘74 running 75 psi and the ‘87 at 57 psi.
 
1 - 20 of 25 Posts
Top