Straight 8 248 oil pressure ??

[ceejay]

HI all,

My car is a 1946 Super 4 door and it has the 248 inline 8.

I was wondering if you guys could tell me what the oil pressure should be on this when hot at idle... Mine is below 30 but rises to 30 or above when driven.

Thanks

[Bill Stoneberg]

Mine runs 40 when driving 30 or so when idling.

Does it matter as long as you have pressure ?

[Aaron65]

After a 30+ mile highway drive you'll be lucky to have over 10 psi in these things. The low end of normal on the gauge is just about 10 psi. Therefore, you're fine. The manual says that as long as you have 35 psi at 35 MPH, you're good.

[smithbrother]

IMO, 10 psi at idle won't hurt a thing, RPM's then are in your favor.

I recall my Dad commenting on this when customers would complain about low pressure at idle, he would stay to them, HOW MANY MILES DO YOU DRIVE AT IDLE? He would smile and they would say, OK SMITTY.....

Just keep good clean oil in the crankcase though.

Dale Smith in Indy

[Ben Bruce aka First Born]

Aaron is correct, per shop manual.

Ben

[ceejay]

Fantastic guys... thanks a lot !! what a relief !!

Just another question un related to the oil pressure topic....

My car doesn't have much in the way of sound insulation under the carpets.

When the engine is running with the gear in neutral, there is a hum from the gearbox.

When I press the clutch the hum stops.

Is this normal for a 3 speed standard trans ?

[smithbrother]

When in NEUTRAL, and the clutch pedal ISN'T being held to the floor, then some of the transmission parts are still moving, WHEN you push down the clutch these parts stop, IMO. Such noise would be from the moving parts.

Dale Smith in Indy

[buick man]

There is an input shaft bearing press fitted into the end of the crank shaft on most manual transmissions equipped cars and some automatics as well. that accepts the input pinion shaft of the transmission. This input pinion is what the throw out bearing rides upon as well. If this is input shaft bearing is worn you will get this hum sound you speak of or at least it will be of a more pronounced hum. It also can make a grinding sound or a wha-wha sound that resonates.

Whenever I change the clutch, pressure plate and throw out bearing I will alway replace the crank input shaft bearing as well.

Food for thought.

[ceejay]

Thank you Dale Smith and David for your valued input.

I did realize that the noise is from the moving parts of the gearbox. What I was wondering is, if this noise was normal for this car.

The input shaft bearing press fitted into the crank of vehicles is in operation only when you press the clutch. Only then is the crank turning with the outer bearing and the gearbox input shaft is not turning as the clutch has disengaged the input shaft from the engine via the clutch plate.

When the clutch is not pressed down, the whole bearing is turning as one unit so even a worn bearing will not make any noise at all at this point.

This bearing will make a noise when you press the clutch, and be silent when you let the clutch out.

My problem is the opposite, the noise is there with the clutch out, and silent with the clutch pressed...

The noise is from the gearbox.... either input shaft bearing or lay gear bearings or the meshing of the lay gear and the input shaft gear.... what I'm wondering is, is this noise normal for such a car or do owners of the same type of car hear a slight noise like I do.

Thank you every one for your input so far... Much appreciated

[Guest Straight eight]

I think the answer is Yes, a certain amount of noise comes from all these trannys. It is the degree of noise that is meaningful. The lubricant style and type also can have an effect. You want a straight 90 weight all purpose gear lubricant.

[buick man]

No, sorry that is not what I stated.

The bearing is pressed into the stern end of the crank shaft and which accepts the input shaft. The inside race of the bearing rides the input shaft nose. The bearing turns constant with the revolutions of the cranks and in sync.

Now the throw out bearing rides on the smooth part of this input shaft. The center race of the throw out bearing rides on this. When you press the clutch in, the face of the throw out engages the tongues of the pressure plate there by releasing the spring pressure which it normally applied to the clutch plate in static position.

What I was referring to is this input shaft bearing can and does make noise when going out as many do not replace it when doing a clutch job. If bad the bearing will increase in sound under torque.

The throw out bearing will make its most noise if the inside race bearing area is worn when it is in free play rotation, like in neutral with the clutch pedal in a resting position. A new noise can also be heard as well when pressure is applied to the clutch pedal causing the worn throughout bearing to apply force against the pressure plate tongues.

If you are driving down the road and apply torque a worn input shaft bearing will also make noise due to the torque even if every other component has been replaced in the drive line.

Hopes this helps.