when i first start up my car i get a good reading of 60 on my pressure gauge, but it slowy drops. and by the end of a 20 minute drive its down to 30 on idle, but jumps back up when i give it gas. i have a oil leak somewhere but dont know what the effect of that would be. the leak comes down on the starter and then drips off the bell housing. i was told this was possible a rear main leak, but seeing as the motor was rebuilt professionally in the last year, and there is no oil on the back of the block or oil pan at all, i have no clue where it is. Can someone relate to this or possible know whats wrong. Thanks

 

84Z,

Your oil pressure seems fairly normal to me. As teh oil heats, it loses viscosity. 30 PSIG at idle is very common and adequate pressure.

As for the leak, clean the engine and monitor it for leaks. You could have a rocker cover, intake, or even head gasket leaking. It's also possible that your dipstick tube is leaking where it meets the block (right above the starter).

 

welli just put a new dipstick tube in, the other one had been broke and barely hangin in there for a while so maybe that was it, ill just have to moniter it i guess, while i was under there today i noticed a clock looking thing on the side of my block and some numbers but the only one i could read said A4, what does that mean?

 

Pressure sounds normal. Once the oil is hot the rule of thumb is 10 psi per 1000 rpm is the minimum required.

External oil leaks if not caused by failed seals are usually caused by excess crankcase pressure. For all the air on top of the pistons there's an equal amount under them as well. The only thing trying to get the air out of the crankcase is the PCV valve. Running breather filters in the valve covers means the pressure has to be pushed out. This excess pressure can also push oil out past gaskets and seals. I use an electric vacuum pump on my race car to evacuate the crankcase pressure since I don't want to suck condensation back into the engine.

Try changing your PCV valve first. If the leak is dripping down onto the starter I doubt it would be the rear main seal. Sounds more like a bad valve cover gasket leaking at the back. Common problem on SBC. Even though it was recently rebuilt doesn't mean the gasket sealed properly. They dry out and get brittle quickly especially the cork style. There might even be a wire pinched under the valve cover causing a leak.

 

The clock is a circle of 10 dots, one dot for each hour of a shift (usually 10 hour shifts). An arrow points to the beginning of the shift an another dot outside the circle indicates what time of day the cast part was made.

 

i aggree with vader and stephen on the oil pressue also. check to see if the dip stick tube is bolted fimly to one of the header bolts. the dip stick tube must be bottomed out with the lip on the tube.