Normal Oil Pressure???

I have recently installed a 1835 motor, 48 Webers, with A/C. What is normal Oil Pressure on a 1835 or larger Motor? My Motor runs around 40 Oil Pressure at idle, then when I turn on the A/C my Motor Oil Pressure goes down to 2o Oil Pressure at idle. I understand the motor does work harder with the A/C on.

Thanks in Advance, Kawika

If the idle speed drops, then the oil pressure drops. If the speed doesn't change, but the gauge reading drops with AC on, then it is some kind of electrical gremlin. At a low idle speed and engine hot, I can see 20 pounds as being ok. Normal idle speed 40 pounds sounds perfect if you ask me.

I go along with Danny's thoughts.......What happens to the Tach/RPM reading when the A/C is switched on???? If you are idling at 750-800rpm and it drops to 550-600, then I would consider that "normal".....Low rpm and hot oil mean less oil pressure.....20 pounds should be good.

Some other things to consider. A VW engine producing 1,835 cc's is simply a stock engine with 92mm pistons and a stock 69 mm crank.

92 mm pistons usually run a bit on the hot side. So, that will tend to thin out the oil which will lower the oil pressure. You might consider an auxillary external oil cooler.

Another thing to consider is the conditon of your engine case. If it has been line bored then more than likely the block is tired. Once a VW engine block gets tired, low oil pressure will be present.

I wasn't a big fan of Gene Berg back in the "day" I used to deal with him on a regular basis and we argued quite a bit...

But, some of his words still hold true. If you have low oil pressure coupled with a very old and line bored engine case then swap to a new case to increase the pressure. Don't add the stiffer springs to the oil bypass as that only puts a band aid on the real problem.

Sorry, probably more information than you wanted but it needed to be explained.

As a true test, get a mechanical oil pressure gauge and screw it into the oil sending switch hole in the upper driver's side of the block. You may need a short length of NPT pipe and a coupler to fit the gauge without fouling anything. Run the car up to operating temp and let it idle, check the gauge and turn on the AC, check the gauge once again.

A good mechanical gauge isn't gonna lie.


Luck,

T


Note: It pays to have a mechanical gauge, a good distributor in tune, a know good coil, a second set of wires, a spark plug or two, and such in your "kit" to use as diagnostic tools. With known good components you can trouble shoot any number of things with ease. Just don't use your "diagnostic tools" as replacement parts, as tempting as that can be.