I've changed the oil pressure unit on the engine, and the reading on the gauge stays low at idle (whcih is normal), but cruisng on the highway, the needle goes only in the middle..

I have an oil cooler in front of the rad..

Is it normal??

My oil pump is ''tired''???

Yes....most Z's have low readings, but of all the engines I've built (about a dozen) there has been no ridge and very minimal wear on the cam, rockers, bearings,crank or rod journals. The books call for 10lbs. of pressure for each 1,000 RPM.

So a reading in the middle of the gauge should be alright then?

A possible improvement to your oiling system would be a REMOTE OIL THERMOSTAT.

From your location I'm guessing that your climate can get cold?

An oil thermostat will do 3 things: -

1. restrict oil from entering the oil cooler until it reaches a minimum temperature, typically 82deg. C.[180deg. F]

2. with an oil cooler fitted it will improve the oil pressure to the engine while the thermostat is closed and,

3. in the event of the oil exceeding the thermostat temperature, switch the oil cooler into the path to stabilise the temperature.

You'll never really know what your oil pressure is unless you fit a mechanical/direct reading gauge!

More info. here!

Usually when you add a oil cooler you also install a turbo pump. I recommend you spend about$15.00 and buy a mechanical oil pressure gauge. remove the sender and use this port. this way you can see exactly what the engine is doing. My gage was reading near zero so with it mechanical gage I am getting 25 psi at idle and 50 psi at 2K on a warmed engine. both are vary good numbers.

Gary

Thanks Gary.

And I'll think about the oil thermostat also, but the car will not see winter at all... waaaaaaaaaaaaaay too nasty here in Qc...

But...to answer your original question, those readings in your first post are pretty typical for a stock gauge and oil pump with or without an oil cooler.

The oil pressure gauge in both of the 240's I've owned always read low. Didn't think they were that accurate to begin with. One mechanic said " high volume low pressure" what ever that means.

Ok, I'll leave it that way then.. Was just worried, since I'm visiting my parents in Charlevoix, near Qc.. 400 miles run to go there..

Just be aware that the gage has no indication of what pressure it is reading. It is just a general indicator. Depending on how it is adjusted it could read anything. this is why I went straight to a mechanical to get the actual pressure at the different RPM . This way when I reinstalled the sending unit I can feel confident that at a given RPM I know what the engine is doing, and what the gage means when it shows near zero , in my case , it means 25psi. Which is fine. At Idle.

Gary

The oil pressure gauge in both of the 240's I've owned always read low. Didn't think they were that accurate to begin with. One mechanic said " high volume low pressure" what ever that means.

Sounds like he was talking about a paint gun.