So I've had my B5 for around a year now. Its a 2001 1.8t quattro sport model with 5-Speed O1A. I recently had the chance to buy an abondoned C5 A6 with the 40V 4.2 for $500 from a coworker. It has no title. So I've spent the last couple months getting the motor in good running condition. changing sensors, gaskets, and servicing the timing. She runs good now. So now, my questions being, can i use the 1.8t subframe, notch it, and get a DTS bar and be fine? With custom motor mounts which i can make myself? And since i have the 1.8 i can use the radiator flipped upside down?

 

I have the exact same car as you. I actually have two of them. My son wants to put a 350ci. in one of them - and it has already been successfully done (I've seen one), so I'm sure you can put the 4.2 in yours (since a 350ci. = 5.7 litres).

The only reason why I wouldn't do the swap if I were you, is because the C5 40V 4.2 only has 295 hp - and that's at @ 6,200rpm

I have 315K miles on my (AWM) 1.8TQM and not only am I'm putting 22psi to all stock internals (and trans) with no issues at all, I'm making (roughly) 250 hp and 240 ft. lbs. (at the crank) at a much lower RPM. The AWM (stock) has 190hp to begin with.

If I wanted to, I could reach the same 195 hp mark w/ relative ease - and I'd be a hell of a lot lighter than you'd be with a V8 swap. In fact, the 250 hp/240 ft lbs that I have now would probably outperform your swapped B5, simply because of the huge weight difference.

In the end: Anything is possible, but I don't (personally) think it's worth it, unless you're putting twin turbos on it and basically doing a RS6 conversion.

That's just my 2 cents.

G/L w/whatever you choose to do.

 

My main reason for doing the swap is the fact that I've run into a multitude of issues with the 1.8. Which now includes the blown k03s. I didnt realize the overboosting until it was too late. The person i got the car from before me had it cranked to 22psi. which ended up overboosting to about 28 and you can guess what happened from there. I have to go to work everday abot 25 miles away and im getting about 10mpg. or nearly $20 a day with a 4 cylinder. I plan in keeping the 1.8 to build up while its out of the car and have the 4.2 in there for the meantime

 

I also have a receipt from a rebuild on the 4.2 showing ~10,000 miles ago. So that helped my decision greatly

 

The reason I have a second car is because of that exact same issue. I put a K04 on the first one and it had a defective wastegate, so while I was test driving it, it had a >30psi boost spike. My gauge only goes to 30psi, so I'm guessing it was somewhere around 40-50 psi, because I threw a piston through one side of the block and the rod through the other side of the block. My engine literally exploded. That was a shitty day for sure.

With a 10K rebuild, that sure makes for a really tough call. I guess you have to weigh the money you would spend doing the swap, vs. the money you would spend fixing your 1.8t

If you have an AWM and the only thing wrong with it is the turbo, I (personally) would buy a cheap ($150) K04 off ebay and see how that does. If you're doing the work yourself, it's a really cheap way to see if you can bring your engine back to life. After all, you'll always have the A6 engine ready to swap, so you don't have much to lose.

If you do end up doing the swap (which I'm sure is possible, but expensive), then I would highly recommend you tune it somehow, because you'll most likely be really disappointed with the outcome if you put all of that work into it, only to find out that the power output isn't nearly as impressive as it sounded before you did it. My personal opinion is - if you do the swap, you have to put twin turbos on it, even if you keep the boost low. That engine can make 500hp all day long. That's a whole lot more than the (relatively shitty) power to weight ratio you'll have with a stock swap and a much heavier front end.

IMO, try a cheap turbo first, boost the **** out of it and wait for it to blow, then your swap will be a must, not a "maybe".

G/L either way.

 

And a k04 will bolt up to the stock manifold?

And yes it is an awm block. I do think its a great motor and has been awesome so far. Besides the fact that i have a cat delete and full straight piped. It was loud before but with the turbo the way it is it sounds awful haha

 

K04 bolts right up. No mods necessary.....and with the straight pipe, you're "tune ready". I can direct you to my guy who can write you your own custom tune and flash your ECM remotely - no down time.

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I appreciate all your advice. I ended up purchasing a k04-015 online. I decided I'm going to pull the 4.2 and save it and really do it right. It's going to be costly but I'm prepared for that. If you wanted to shoot me over some information that would be great! Thank you very much

 

Sounds like a good plan.

Here's my guy's website (he's awesome): https://www.reflecttuning.com/

Tell him Chip sent you and he might give you a discount.

G/L W/everything!