I recently saved my newly bought Camaro from a spun bearing by swapping in a motor I bought online. The seller informed me that while the engine just sat in his el Camino for almost a year, it was and should be good and he would reimburse me if it wasn't so I trust that it is problem free.

I did a full tune up and dropped it in, and it fired up right away, but with some nasty lifter tap. I ran a bit of atf in the oil and after about 15 minutes, it went almost completely away, except for a slight tap/squeak at higher rpm. I literally blew my budget and then some on this swap, so how long can I drive it while I wait for it to either clean itself out or determine that it's just bad? Is it going to wipe my cam or something equally bad anytime soon? It's my dd and I probably won't be able to replace the lifter for about another month of almost daily use.

 

Did you try adjusting the valves? I would try that first, no amount of additives will help it its out of adjustment. I had some luck on the 305 in my truck with marvel mystery oil. Just substitute 1 quart of mystery oil for a quart of oil when you change it. If is safe enough you can leave it in the whole oil change, I only ran it 500 miles before my ticking lifter quieted down.

 

that was going to be my next step, if I absolutely HAD to. I literally blew my wallet up fixing stupid problems along the way with the swap . I ran it a few times today trying to diag my tranny problem and it seems like it's working like it should now. The engine did sit for almost a year so it was probably just dirty, and i get hypersensitive to noises when i do a big job like that.

 

Adjusting the valves won't cost you a thing (unless you rip a valve cover gasket)!
Are you familiar with the procedure?

 

You don't want to use any cleaners like Sea-Foam. Fact is the fixes in a can like that also cleans out deposits in the entire engine where those deposits are taking up clearances on some worn parts. A oil additive,ok,but stay away from trying to clean it out because that can get risky. I think the lifter(from what your saying)bled down and needs a chance to pump back up. It could not have anything to do with dirt.

If the cam has a bad lobe no matter what you do there isn't a fix in the can that will matter.

How about the seller giving you the money back to fix it by tearing it down to diagnose it and repair the issue. Sure would be cheaper for him to do that over a full refund.