Hi black455, do I ever sympathise. Jeez, been there… done that… got the T shirt. See if I can help.
I was in the exact same position many years ago. I spent a big chunk o’ time trying to do the same thing. Well, I’m not trying to be negative, and I don’t want to piss on healthy ambition, but in the interests of trying to save your own time, resources and mental stability, it’s basically a waste of time.
Sure, you can tape over the erase head. This rarely works adequately, and you will tend to get significant unhappy leakage. Even if you do it, it’s usually hard to then hear track 1 AND record track 2 in sync, because the record and playback heads are normally at different places on the tape. Even then, the sound quality won’t be up to much. I don’t know about every 4-track in the world, but most run tape at double normal speed, and have some pretty souped-up Dolby B or C, just to try and get some decent sound quality.
As Montfort says, consider searching for a second-hand or auctioned 4-track, on the web or in real life. Stick a few want ads around, see what you get. Or get a job in a music gear shop - you’ll perhaps get to ‘borrow’ kit or get it at a discount, and you may become pals with the sales rep from some company that does multi-track gear, and work something out.
Another idea - ditch the notion of brown tape altogether. Assuming you have a PC, or access to one, the ‘virtual’ recording and mixing desks that run on PCs are amazing. Sure, top of the range software like Cakewalk costs money, but there’s always a shareware alternative that might be enough to get you going. Digital computer-based recording has a lot of things going for it, so you might want to poke around in that area. I know a couple of guys who work in the music industry and can get hold of any kit they want - and they have both entirely ditched their home tape setups in favour of computer-based equivalents.
If you can’t afford either a multi-track or a computer, then you might want to look at hiring, renting or leasing multi-track gear. Spreads the cost, but is obviously more expensive in the long run.
Lastly, try getting work in a recording studio. Don’t say “I’ll do anything, I’ll even make the coffee”. They don’t need people to make the coffee. Offer some useful service or work, and do a deal about x hours recording time. Maybe find a studio or some musicians who want a website setting up, so you swap your website creation skills for money or studio time. I’m assuming you have some website creation skills. If not, fork out for a book by Elizabeth Castro, “HTML for the world wide web”, part of the Visual Quickstart Guide series. Brilliant book, teach you all you need to know in a week!
Good luck!