In the off season I did a top end rebuild on my carb'd 502 Mag. So far this season it seemed to be running good. So this last weekend I was running in on a smaller inland lake wide open and it lost oil pressure. I trailered it home and put a manual gauge on it just to make sure it wasnt a fluke. It indeed has zero oil pressure. It will still turn over and start no problem.

Has anyone had this problem before with these motors?

I am sure this thing is going to need to come out and get torn down, but is there anything I can check before the entire motor comes apart??

First,,,,, pull the dipstick and make sure it has oil,,,,,,next guess,,,,, the oil pump pick up fell off

Yep, most likely lost the pickup.

Always tig weld the pickup to the pump and ALWAYS check to be sure the pickup is the correct distance from the bottom of the pan.

what should the oil pressure range be on a stock 502 mag carb version?

Mine always ran between 40psi and 80psi depending on rpm and oil temp. I ran synthetic 20w50.

Thanks for all the info everyone! What are the odds that everything inside the motor isnt destoyed??

If Fram oil filter, try replacing it.

Other than that, motor out, ck for oil pump pick up as stated, and either way ck some bearings.

Cut the oil filter open and look for metal. It could be as said above the pickup came off or possibly the oil pump drive shaft broke. Maybe you will be lucky and have no damage if you caught it immediately. Bearings wiped out would still show oil pressure just bad oil pressure, but not zero.

Thanks for all the info.

I am just hoping there is a tiny chance I could get lucky and replace the pump or fix the pickup and be ok. However the way my luck has been with this boat I am not holding my breath

i believe the pump is submerged in oil. even if pickup comes off you should still have oil pressure. just in case, add 3 more quarts above full. now you KNOW bottom of pump is in oil. see if it gets pressure then shut it off and start pulling...as long as pan is off, main and rod bearing replacement is quick and cheap. just make sure they are the right undersize...

I'd pull the distributor, inspect oil pump driveshaft, and try turning the pump shaft with a priming tool. total oil pressure loss, sounds to me like oil pickup, oil pump simply failed, collapsed filter, or something like that.

Any reason you did the top end rebuild other than upgrading? in otherwords, did you lose a lobe on the cam or anything prior to the top end rebuild?