Engine: V8 RPM at 40 MPH

[5brown1]

The manual for the 1955 V8s says 20 to 40 PSI oil pressure at 40 MPH. As I have a non stock transmission I would like to know how many RPMs a stock 1955 Studebaker V8 will be turning at 40 MPH.
Thanks.

[rockne10]

RPMs at that speed from a stock model are going to greatly vary, depending on transmission: standard, standard w/OD or automatic, as well as rear gear ratio. What is your "non-stock transmission"? What is your goal? How is the car used?

[Tom Bredehoft]

If you've got oil pressure over 20 or 25 pounds and don't rev it up to 5500 every (or any) time you shift, your engine will live forever. DON'T SWEAT THE OIL PRESSURE.

[DEEPNHOCK]

Have you serviced your oil pressure relief bypass valve?

[altair]

Rpm @ 40 mph

The manual for the 1955 V8s says 20 to 40 PSI oil pressure at 40 MPH. As I have a non stock transmission I would like to know how many RPMs a stock 1955 Studebaker V8 will be turning at 40 MPH.
Thanks.

Looking at some early datta a stock '55 259 V8 would have a 3.92 rear axle, with a standard transmission top gear is 1 to 1 based on that information and applying some simple math it works out to 2000 RPM @ 41 MPH I hope this is correct Dave

[rockinhawk]

Never paid much attention at 40, but my 57 Silverhawk in 3 od turns 1900 at 60.

[bosshoss61]

2000 @ 41,,,(on a V-8),,maybe 2000 @ 61 sounds like she's really car-anking at 40 MPH

[5brown1]

I'm asking because the motor has all new bearings, new OP relief, newer style rockers and oil pump rebuilt. The oil is restricted to the filter and the plug below the dist. is in place. With 15-40 Rotella the pressure is high (50+ psi) on start up and then drops to no more than 20 psi when warmed up and driving at 2000 RPM.
I've read all the posts about low oil pressure but have never seen anything about the RPM at which the oil pressure should reach satisfactory levels. Since it is related to the RPM rather than the speed I want to know if I need to be concerned.

[bosshoss61]

Things I read about Shell Rotella say it's mostly for diesel pushers. And I'm assuming it's not a diesel? If it's gas --50+ pressure sounds reasonable on 40W oil in colder atmospheric conditions. And yes, speed is secondary to RPM with all the different gear ratio's and tire ratio's. I would not be concerned with the pressure. In my opinion even 5 PSI is enough to pump oil where it should go.

[rockne10]

The "idiot" light on a Lark doesn't come on until pressure drops to under 6 lb. I would only be concerned with pressure at hot idle. Out of curiosity, did your rebuild include cam bearings?

[5brown1]

Cam bearings are new.

[altair]

Rpm @ 40 mph

2000 @ 41,,,(on a V-8),,maybe 2000 @ 61 sounds like she's really car-anking at 40 MPH

My math could be off for that configuration. I have a 1992 Ford Explorer automatic, in drive it is safe to say that it is direct the same as in a standard, the differential is not the same but in the high 3s, at 40 MPH the tach was reading between 1900 and 2000 RPM. It is equipped with OD and the RPM is only a little bit higher 22-23 range at 60 MPH and with the lock-up it drops another 100 or so. If the 55 was a 224 the 2000 at 40 mph would give you decent performance in town then coupled with an OD it is conceivable that the RPM may only be slightly higher at 60 MPH (maby 25 or so)

[PackardV8]

To bottom line your original question, yes 20# warm 15w-40 at 40 MPH or 2,000 RPMs is too low. On a newly rebuilt engine with new cam bearings, I'd expect to see more like 35-40#. I'd install a temporary 270*-sweep mechanical gauge to check the original.

At idle, 5-10# or as long as a warning light doesn't come on, it's fine.

What is the water temperature?

jack vines

[5brown1]

The gauge is a new SW bourdon tube type. I will try another gauge when the rain and snow stops. The temperature is steady at about 180.

[5brown1]

Jack,
I borrowed another gauge from a mechanic friend. Results after getting the oil hot: idle at 750 RPM = 10 PSI 2000 RPM = 28 PSI 3000 RPM = approx. 40 PSI
Apparently my new gauge is not very accurate. These numbers are somewhat better - what are your thoughts?