131mirafiori forum

Hi All,

What oil pressure reading in PSI should I be getting for my 2ltr twin cam, say at idle (900 rpm) 2000 and 3500. I've done  recent rebuild with complete engine balance, new main and big end bearings, full set of gaskets. Oil pump was checked has no freeplay slop and in tollerance when measured with feeler gauges

I have bought a new TIM oil pressure gauge and am getting readings 60 psi on start up then when warmed up I get 10 psi at idle, and 40 psi when driving approx 2000 rpm and approx 50-55 psi at 3000 rpm. Just changed oil and filter and put in Mobil 15w/40 multigrade oil.

What are your readings like? or is there a set way to take readings?

Regards

Keith

Your readings seem about right to me. These engines are high flow rather than high pressure for oil. But I'm surprised that you've rebuilt the engine and  reused the old oil pump. I subscribe to the idea of always fitting a new oil pump when rebuilding the engine.

I rebuild many engines and never fitted a new oilpump. Why? They don't wear out. There's always plenty of oil to lubricate the pump. Except for an engine run dry ofcourse  ;)

I always use 20w50 oil, the thinner oil used in your engine is probably the reason for your concern. I've never replaced a pump either, unless the splines on top of the shaft are suspect, I haven't found a pump yet that looked excessively worn internally or didn't measure within specs.

Thanks guys,

The pump was checked for wear etc. and didnt need replacing, and there is plenty of oil getting to the cam/rocker boxes so I knew that there is not a pump or circulation problem I just thought that I should be getting higher readings but Thotos answered my concern re high flow engine not high pressure.

Correction regarding the my oil readings, idle is 15psi, 2000 rpm is 55psi and 3000 rpm is 70psi. Just for the sake of it could someone compare their readings to mine. I checked the readings while the car was stationary.

Thanks Guys

Keith

Re: rebuilding engine and keeping old oil pump.

There is nothing wrong with using an old oil pump, for a newly rebuild engine however...

If the engine is been modified for sport it makes sense to :

a/ make sure the pump is in full working order
b/ increase the oil pressure the pump will provide

Both are very easy.

Miro 

How is this done Miro?

Keith,

Really simple
   
you just add a 2 mm washer under the spring of the oil pump.

Miro 

That will just change the point at which the relief  valve opens. It will not make the pump generate more pressure at a given speed! If you want to change the maximum pressure allowed by the relief valve, change the spring for a stronger one don't add washers!  ;) That's just like stretching the spring which is another old trick!  ;D If you want to generate more pressure out of your oil pump, you either need to change the tolerances inside your pump or increase the pump speed.

Theo,

Opened up two oil pumps recently. Seem to have missed the valves  ???
 ;D

Well I was going to say that the oil pressure relief valve is not in the pump for the Fiat twin cam engine (they are within the pump on some other engines) but I assumed that when Miro said "washer under the spring" he meant the spring inside the oil pressure relief valve. That's the spring I meant and I never said it was inside the pump, it's Miro that said "the spring of the oil pump" ;) ;D ;D

That's why i was confused. There are no springs or valves in standard pumps. There are only two gears that push the oil up.
 :)

Exactly. So the only way to have more oil pressure from the pump is to either have different gears or have them meshing closer together or spin them faster. In any case the oil pressure is developed by the engine and not the oil pump; the pump needs to deliver the oil to the correct places.

Nope, their is a spring in the pump and its a relief valve spring for the pump itself (page 131 GC Modifying and tuning Fiat/Lancia Engines).

And before refitting any old pump please please remove that gauze and check behind it, look what i found hiding behind mine?


(http://i435.photobucket.com/albums/qq71/parrish_028/PB231152.jpg)

Hi Parrish,

Interesting find, Heh

Keith