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Oil Pressure Gauge

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M

MCS

Jedi Warrior
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Hello,
Is it possible that I have air in the oil pressure line? When I reinstalled the line after my rebuild I did nothing other then refit the line.
What seems to be happening is the oil pressure will drop off to around 30 during idle, but this an intermittent drop. Most of the time the pressure sits around 55 psi at idle. Tonight when I was driving the pressure dropped off to 10 psi and I slowed down to stop and then it jumped up to 60 psi.
Wondering if air in the line would do this. I think maybe I should go get a cheap aftermarket gauge and see what happens. Any ideas?
Thanks Phil
 
Air in the line is no problem--all oil pressure gauges of that type have air in the line.

I don't remember what flavor of spridget you have. The earlier cars sit around 50-60 psi when cold, even at idle, and drop quite a bit as they warm up. 10 psi, hot, at idle, is a little low, but not totally out of line. (Dunno what the situation is with 1500s.) If the 60 psi reading is the wrong one, it doesn't sound like a gauge malfunction to me; but I suppose that's possible. I'll let the engine guys speculate as to possible engine causes.

Yes, if it were me, I'd get a second gauge to monitor what's going on. they're cheap.
 
The engine is a 1275 bored out to 1363cc. Everything is basicaly new. It has about 300 miles on it.Runs great and seems to have good power. I wonder if the oil pressure relief valve could stick and cause a loss of pressure. I replaced the releif plunger with the ball bearing when I rebuilt the engine.
Thanks Phil
 
Another thought. When I first start the car cold oil pressure is 85 psi, and as it warms up it drops to about 65 psi. I wonder if I have to high oil pressure and then the releif valve is opening during cruise.
Phil
 
MCS said:
I replaced the relief plunger with the ball bearing when I rebuilt the engine.
Thanks Phil
Click to expand...
Why not the original plunger or a new same design replacement? Different is not always better. Due to the way the relief is constructed, it would be easier for a ball & or it's spring to get hung up in a partially open position. The original plunger has somewhat straight sides to help guide it straight in it's bore. The ball & or spring can more or less get caught on the sides of the plunger bore & not completely seat at all times.

From the description, the pressure is erratic & not very predictable which would go with a ball "plunger" that is not always correctly seating.

I realize that the ball is "supposed" to be an improvement over the plunger but sometimes things are not as they would seem.
D
 
I went with the ball because of what Vizards book said. Many people seem to go with the ball with good results. I am going to try the plunger today and see what happens.
sure hope it works, I got over 5 grand in this rebuild
Phil
 
Phil

Make sure you are using a good oil in this rebuilt engine like VR1 20-50.Let us know how you make out.

Cheers

Mark
 
The ball bearing fix is typically considered an improvement (particularly on the transverse A-series) as it is less prone to binding due to swarf picked up and passed through the oil to the filter.

When you fit the ball bearing did you remember that you are supposed to shorten the relief spring? The common method is to buy a Cooper-S relief spring and start by cutting off about 2 turns. After installing and running the engine for a while you determine if more needs to be removed and cut off about 1/2 turn each time as necessary until you get a cold idle pressure where you want it (somewhere between 50-60 PSI).

An acquaintance in OZ takes this a bit further. Once he's gotten the spring the length he wants, he takes a steel dowel or rod (I think he said 8mm or 5/16" in diameter) and cuts it to some length (sorry... I forgot the length) and he places that inside the spring to keep it from flexing sideways as Dave suggested above. My friend says this added step has always given him very steady oil pressure.
 
Phil,
Please post your results of replacing the original plunger back into the engine. As Doug pointed out there is a bit of fiddling with using a ball bearing and cutting the spring and or shimming one to make it all work.
I know there is a lot of good buzz about the attributes of this route. I will say long term, I’m certain the history of the A-series engines have never proven the pressure relief spring or seat to be a weak spot. I’m not real certain a ball bearing of 60+ Rockwell (hardness) is a good long-term against an 18-20 mild steel Rockwell seat. If your original plunger looked good and the seat it seals against is in good shape then….
Maybe treat your new engine to a new spring I think it deserves it.
“dug”
 
Thanks for all the interest.
Well I have a brand new spring and relief regulator with a very nice machined nut. I purchased it from APT. They told me it would probably fit with a bit of work, grind off the starter ear. That would not work so I went to my spares and found a well-used spring and plunger. Measured the spring it is 2.86 inches, just like the manual says. Took her for an afternoon drive.
Observations.
On first cold start-PSI now 65 was 85
After she is warm sitting in the garage was getting 40-50psi
After driving for about 40 mins, the oil psi at idle slowly drops to 25-28 psi, no lower. When I rev her out it jumps back to at least 50 and stays there for the cruise.
I was really hoping for a little higher oil psi at idle. I drove the machinist crazy with my crank and rod clearances of exactly 1.5 thou as Hap recommends. The good news it almost does not leak oil, seems to leave a drop on occasion, not sure from where.

I am using VR1 oil/ 20-50 the stuff Hap likes. I forgot to cut the relief spring, so it was way to long with the ball bearing. I will order a brand new plunger and spring next week, must be the only part I forgot to replace.

Would like to go for a real cruise but my wife and kids have to many other jobs for me. I will post any additional observations I find. At the moment I would say psi looks more stable, but need to drive more. Have a load of pics I need to share, just got to get to them
Thanks Phil
 
If it is any consolation, when I put my transverse A-series back together all its clearances were tight and of course, it had a new oil pump. Like you I was very pleased with the cold oil pressure. However, when hot, my idle oil pressure at 1000 RPM is somewhere between 35 and 40 psi. There's nothing wrong with that pressure... but I expected more with all the new parts and good clearances.

Dug's comment on the relative hardness of the relief valve components will remain a subject for debate. One of the two parts is going to wear, that's for sure. You'd think you'd want the removable part to be softer so when it wore out you could replace it easily. However, if the removable valve component wears in a manner that prevents it from seating it's not an effective solution. The debate will continue.
 
 
Yes it is beautiful, my wife tells me her horse is beautiful, she says I am sick
Phil
 
20 lbs at idle is outstanding in fact.
 
85lbs? Im not too savy on the A series but what is the oil pressure reilif valve suppossed to kick in at? My 1500 is set at 60lbs. Never goes over that, cold or hot.
 
60 lbs cold, 50 hot

35 or so idle cold. 20 hot idle.

And that would be ideal.

It's all in the book.
 
Put a 100 miles on today, now that I have the correct spring and the original plunger, psi was always between 25-30 during idle and cruise was 50. Interesting observation, when i previously started cold and let it idle I it leaked a very tiny amount of oil. Since the change and the lower oil psi at start, I see no drip. It was a very small drip, but after Jacks oil experence I was so careful. I must again thank you Jack, you really helped me and motivated me to triple check everything. I sure wish you could all listen to my sprite it has a beautiful sharp sound. My neighbour says it sounds like it has 800 horse under the hood. That makes me smile.
Phil
 
What's your engine RPM when you've got that 25-30 psi hot idle pressure?

It must have been a great day to take the car out for a 100 mile drive. I'm glad the weather and car were agreeable!
 
It was a great day, 23c. i even managed to fly my model helis. Did nothing useful, just played.
I have my idle at 900rpm, using the swiftune SW5 cam, oh it sounds so good. Must say the HIF44 carb is very easy to tune, miss the look of the twin Su's but there is a big performance improvement with my setup.
Phil
 
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