I have registered today and i'm pretty much a noob on cars.

Ok, here are my questions.
I bought the mazda6speed about a year ago, and found out that my number 3
wasn't working properly. O2 sensor is out. and there might be a possible valve bent. According to the mechanic (my cousin), it is not wise to swap the same engine and run from it cause it might have same problem and i'll end up coming back to the first problem. (the engine was dead at first, and he came and fixed it somehow)
Now, he's saying even tho its running, he can't say it will last long.
So, here i am. Trying to decide which way to go.
Fix the car properly and drive from there or sell the car and take the loss which is about $7k.

Is there any possible engines that could swap without too much of a headache? like sti engines or chevy ls1 engines and such.
I know it sounds noobish and i know i'm noob
Please help. I need a good solution out of this.
either way, i'm spending close to $6-7k.

 

The cheapest and most hassle free swap is going to be just dropping another DISI turbo engine in there as that is going to be your only plug and play solution. Swapping in a different engine would be a pretty big project, and not something I'd recommend to a person that is new to this stuff. As for it being a bad idea to swap in an engine of the same kind because the same problem could occur....well that's just about the dumbest thing I've ever heard. Yeah, you could have the same problem occur, but you could also have it occur on any engine so his reasoning is highly flawed. Seriously, save yourself a big headache and just get another of the same engine and drop that in there, that is if the engine truly IS fouled, which I'm not convinced it is as valves and o2 sensors can be replaced. Also, get a second opinion from another mechanic before you go and drop a bunch of money on a new engine.

 

so, if i still want to have my car get fixed somehow. I prefer swapping with different engine than a DISI turbo. Possibly little bigger engine? maybe? and roughly how much do i expect for doing this?
I'm driving 03 civic and it is really boring ... -_- I can't wait to pull my 6 out from the garage asap.

 

It's going to be extremely expensive as it's not a common chasis so there are no kits like there are for 240sx's and the like. So, they will have to create the mounts for the engine, redo the drivetrain, create a new wiring harness so that everything plays nice together (even then you're not guaranteed to have everything work right), a new transmission will likely be needed, and then there will be the inevitable laundry list of miscellaneous parts that will be required that I'm forgetting. An engine swap on this car is a huge task, especially if you are wanting to retain functions like AC. I can't give you a number off the top of my head but an LS1 crate engine is in the ball park of $5k by itself and my guess is that you will be looking at atleast that in labor to get the silly thing to fit in the car, which will present you with another problem as the engines in all 6's are mounted transversely rather than longitudinally so you can more or less forget turning this thing into a 4 door vette cause it would take stupid amounts of modification to make that happen.

 

I'm afraid your ONLY THREE OPTIONS are as follows:

1. Figure out what's really wrong with your engine and have it fixed
2. Replace the engine like-for-like
3. Sell the car at a loss and buy something else

Doing ANYTHING else is going to be prohibitively expensive (like way over $10,000; in fact, I'd bet well over $15,000) and, dare I say it, stupid-stupid-stupid.

Do yourself a favor and listen to CKeffer.