General Maintenance & Repairs - Pretty gnarly oil leak coming from passenger side...

I have rebuilt 241 heads on a 99 LS1 block. Everything is topped off I start it up no problem, no leaks it starts off at around 50 oil pressure but when I drive it around the block my oil pressure tanks from 50 to 35 and stays there!! As soon as I get back to the driveway it starts dripping little by little. I even bought a dye kit and that did not help because the entire starter, bottom of the engine is soaked in fresh oil from half of the oil pan to where the trans meets the engine and the rest is just sprayed onto the headers. It's coming from the passenger side and I checked the Oil Pressure Sender and it's fine.. Any takes on where this is even coming from?? :bang:

Did you have the valve covers off recently? If so, look at the back of the valve cover and see if its coming from there.

Yes I had the entire top portion torn down during my head swap as well as the valley covers to do some cleaning inside and out. I didn't see any oil coming from the sides but I didn't check the back, I can't see how it would soak the starter and entire bottom half if the valve covers were leaking.. it's pretty bad.

Its worth a shot to check it out. I had the same exact problem and found the leak at the back of the valve cover.

Did you seat the dipstick back in the pan properly? Did you check the o-ring on the dipstick tube? That will let lots of oil out in the exact spot your talking about.

Also it's not uncommon for new valve cover gaskets to bulge out of the groove or be loose fitting. The blue FEL-PROS seem to be the best I've used next to actual GM gaskets.

Hopefully you used all new gaskets on the top end? Most people say to reuse some gaskets but, imo just buy new after ones if they've been on there longer than 5-6k miles. Cheap insurance imo.

sounds like the oil pressure sending unit to me. That is the only thing that would leak bad enough for you to lose oil pressure that quickly

Yea thats a pretty big leak. If you wanna be sure wash it all down first, THEN add the dye and as soon as you fire it up be ready to search around with a UV light. If its only a 1 oz bottle of dye I'd put in at least two. Sounds like you added the dye and waited too long to check it.