[Sirrotica]

If the pan has dirt, or rust in it, you're not going to be able to start it, and hope the oil filter keeps it out of the bearings. If the bypass valve opens, all that crap is going right into the crank, bearings, and lifters, ruining every internally lubed part as well as filling the oil galleys with abrasive crap that can only be removed by completely disassembling the engine. Even if the engine was good when parked, it likely will be junk by just running it any length of time.

Having run dirt track cars (Pontiacs exclusively) for many years, and seeing first hand how just a tiny bit of dirt grinds up engine parts in a very short time, I would never recommend starting any engine that you know has abrasive bits inside of it. As large as the pores are in a conventional oil filter, all the fine particles will pass right through it anyway. 40 microns is the usual size of the media pores in most full flow oil filters, 40 micron particles will score any internally lubed parts.

Pull the engine, and look at everything that is covered by tin, (pan, valve covers, and valley cover) to assess what your working with. Pontiac oil pans have been known to rust through, especially if it was ran in a road salt environment they rust from the outside in. If they have water in the pan, I have seen them rust from the inside out. A pinhole could easily empty the pan over decades.

Crossing your fingers and hoping the oil filter gets all the dirt, and retains it, is foolish in my opinion, and I turned wrenches for over 50 years for a living. Even if the oil filter is successful in catching every abrasive particle, there's a good chance the oil pump screen will plug up, and starve the engine anyway. I wouldn't give you a 10% chance that you'll be successful trying that scenario.

On a Trans Am, if the car sat outside, the hole in the hood will let water run down onto the valley cover where it pools, and will eventually rust a hole through the valley pan, letting water run into the oil pan. I've seen two Trans Ams with rust holes in the valley pans that were left outside for extended periods from rain water.

In the end it's your car, and your choice, you have to make the call.