I have a 355 chevy in my 86 when i first start up oil pressure reads at 60 after maybe an hour of driving i lose oil pressure down to bout 40 shut it off then turn it back on pressures down to bout 20 nd motor stalls out unless i stay on the gas later after letting it cool the pressure is back to 60 what is going on?

 

sending unit maybe bad, oilpump bypass messing up or the bearings are getting worn.

But mostly oil thins out after it warms up.

 

40 psi hot is about what it should be.

 

So maybe an oil change could solve this?

 

Maybe.

But as said, those pressures are pretty much about normal for yerbasic stock SBC oil pump.

The "stalling" is not related to anything to do with oil pressure, except that of course when the engine "stalls", the OP goes to zero.

I'd fix the carb and make it run right, and leave the oil system alone, if it was my car.

 

[quote=sofakingdom;5016223]
But as said, those pressures are pretty much about normal for yerbasic stock SBC oil pump.quote]

I believe its a high volume oil pump as they usually run at 60 (at least this is wat ive been told)

 

A high volume pump moves a high volume of oil. Has nothing to do with pressure.

The relief spring installed in the pump determines the presssure that it will develop before the bypass opens and relieves the pressure.

Normal stock SBC oil pumps such as might typically be used in a rebuild typically have a spring that gives about 35-40 psi of pressure. Which is plenty.

Not sure how having 60 psi cold makes you so sure this is a high-volume pump, anyway. Again, pretty normal behavior; when cold, not enough of the thick oil flows anywhere (including into the bearings), so the bypass can't let enough out to reduce the pressure to its set point. Then when the oil gets to its normal temp and reaches its normal viscosity, the system starts to be able to work normally.

All in all, sounds mostly normal to me.

 

[quote=sofakingdom;5016457]A high volume pump moves a high volume of oil. Has nothing to do with pressure.
Not sure how having 60 psi cold makes you so sure this is a high-volume pump, anyway. quote]

As i said that is wat i have been told

 

And that counts for .... what? Are the parts listening?

Well not much I can do about that. Time to let go of the myths from the past. Can't help that you were "told" a bunch of fantasy-land make-believe at some prior point in history, all I can do is tell you THE TRUTH now.

 

Tht would be great so i can get it fixed

 

Get what fixed?

 

whatevers causing me to lose oil pressure and nd not allowing it to run after restarting it

 

There's nothing wrong with the oil pressure you describe; it's completely normal. Nothing there to fix.

No connection to the "stalling".

I'd start on the driveability problem by maybe checking the ignition system for the usual obviou culprits; maybe do a tune up (plugs, cap & rotor); plug wires if they need it; just generally make sure all that is in perfect condition.

Then if that doesn't fix it, rebuild the carb, and tune it.