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View Full Version : B5 4.2L swap from 05' B7 S4. do's and dont's



Sapperzero
05-15-2018, 01:00 PM
What up people! so i want to put my 4.2l into a B5. the 4.2l is out of a B7 S4, i know the engine is backwards in the B7. does that affect how i put it in? whats the difference between the B7 S4 4.2l and the C5 S6 4.2l?? AND ANYONE IN THIS DAMN COUNTRY THAT DOES CUSTOM WIRING HARNESSES!! thanks fam!

ZimbutheMonkey
05-18-2018, 05:32 PM
Look, while I don't want to discourage you, if you're asking those questions you're just going to end up with a half finished shell of a car that you sell at a massive loss unless you're into arson and insurance fraud...

My advice if you want to do a motor swap, sell the V8. They sell all day for about $4000. Take that money, buy a cheap 2.7TT with some blown turbos, put a set of Franketurbos on and some ebay downpipes, buy 550cc injectors, clutch, tune and drive around with 400 AWHP all day...

Or, install the frankenturbos with a stock tune until you can afford the rest.

The 2.7TT swap is much more well documented and will save you 100's of hours of headache.

Sapperzero
05-19-2018, 01:14 PM
All i want is a v8 B5. i would rather have the 4.2, its nice in the b7. all i really want to know is how much different is the 05 S4 4.2 and the 02 A6 4.2(if that's the right year). im not worried about the swap.. i just need to ultimately know if the "backwards" 4.2 can just be "turned around".. is this the reason i only find A6 4.2's in B5's.

Jsol
05-19-2018, 05:05 PM
The engine isn't "backwards". They timing chains are on the back of the motor. If you were going to "turn it around" where would you put the gearbox? Through the radiator? A B7 V8 could be put into a B5 without much more hassle than a belt driven. Although in your case I wouldn't take it on as it seems beyond you. Please don't take this the wrong way, just trying to save you some pain.
If, and that's a big if, you were going to go with the B7 V8 you would want to take off the back timing covers and ascertain the condition of your guides/tensioners/adjusters and replace if necessary. Save some grief down the track.

LA4
05-19-2018, 07:27 PM
All i want is a v8 B5. i would rather have the 4.2, its nice in the b7. all i really want to know is how much different is the 05 S4 4.2 and the 02 A6 4.2(if that's the right year). im not worried about the swap.. i just need to ultimately know if the "backwards" 4.2 can just be "turned around".. is this the reason i only find A6 4.2's in B5's.

You're either trolling, or vastly under-estimating what it takes for a swap like this. If you are talking about the engine being "backwards" and "turning it around" you don't even have a theoretical understanding of how the cars work, yet along the skills capable of executing and putting this all together.

Buy a B6/B7 S4 with the chains already done. You might argue that the B5 is better-looking (I wouldn't disagree) but in the end you will have a running/driving car as opposed to a half-baked money pit with your flywheel in the location where the accessory belt usually resides.

Cactus Avant
05-19-2018, 09:50 PM
To answer your question about the B7 S4 and the C5 S6 4.2s; the main difference is belt driven vs chain driven. I would personally go with a C5 A6 or S6 4.2 if you were to do a swap, just because there is a lot more information out there right now involving fitment and wiring with those earlier V8s. I believe the size of the B7 4.2 is a little bit different and you may run into fitment issues, as it is already a very tight fit in a B5. The B6 and B7 S4s have something like 4 radiators to keep it cool, while I don't believe the C5 does. There may be some cooling difficulties with the B6/B7 4.2 in the B5. Thats just another possibility to consider. Finally, the B7 S4 ECU will likely be more difficult to mate to the B5 because of its CAN-BUS system.

Moral of my story is, if you want to do the swap, really do your research and use an earlier engine to save the headaches.

Plus, you can get 4.2s from A6s all day for reasonable prices, whereas the B7 4.2 will sell for ~$4k like ZimButheMonkey said. Save some money and get the older 4.2

Sapperzero
05-21-2018, 07:38 AM
Thank you for the information and not just calling me a dumb ass.(@Cactus) My reasoning to the question is that I bought a B7 S4 and got shafted.. I had a B5 years ago and absolutely loved it, couldn't find another one at a reasonable price when I was looking for one, last, but found the B7 so I went with that since my buddy was telling me about the 4.2. I didnt know that the 4.2's were different between years until after I bought the car... Ever since I've been trying figure this thing out but nobody talks about it... And now I see why... So, basically, I have a B7 S4 with a blown head gasked and some weird drivetrain tremor (was told it had something to do with my clutch sensor) and need it gone... If its pointless to keep the engine for a swap then whatever...

Sapperzero
05-21-2018, 07:43 AM
The engine isn't "backwards". They timing chains are on the back of the motor. If you were going to "turn it around" where would you put the gearbox? Through the radiator? A B7 V8 could be put into a B5 without much more hassle than a belt driven. Although in your case I wouldn't take it on as it seems beyond you. Please don't take this the wrong way, just trying to save you some pain.
If, and that's a big if, you were going to go with the B7 V8 you would want to take off the back timing covers and ascertain the condition of your guides/tensioners/adjusters and replace if necessary. Save some grief down the track.

Ultimately, yes, it is and i know.. i just have a blown head gasket on my B7 and don't want it. I'm not electrically inclined, more mechanical. I'm not worried about "doing the work" as i am just making sure that what im talking about is either doable? or should i figure out how to sell my B7 in its condition? i want the 6-speed though.

walky_talky20
05-21-2018, 07:43 AM
I think it would be wiser to just fix the car you have. There's no re-engineering anything, just repairing a regular car with regular parts. All of which will be covered in a regular repair manual. Then you'll have a nifty S4 (with V8!) to tool around in.

If it's automatic, and you want a 6-speed - just sell it after you fix it up and find the car you want. My suggestion would be to get a car *without* an Audi chain-drive V8, but that's just me.

Sapperzero
05-21-2018, 08:07 AM
what about the B7 6-speed in a B5?? Is that do-able??

walky_talky20
05-21-2018, 10:21 AM
Yes. The B7 S4 6-Speed transmission (called the "0A3") doesn't bolt up to the B5 mount locations, but you can purchase or make brackets to get it to fit. You also need a shortened B5 S4 driveshaft and some other stuff. This page has some details:
https://jhmotorsports.com/jhm-b5-s4-c5-a6-allroad-2-7t-engine-originally-01e-0a3-6-speed-manual-transmission-conversion-swap-parts-list.html

Sapperzero
05-21-2018, 10:24 AM
Yes. The B7 S4 6-Speed transmission (called the "0A3") doesn't bolt up to the B5 mount locations, but you can purchase or make brackets to get it to fit. You also need a shortened B5 S4 driveshaft and some other stuff. This page has some details:
https://jhmotorsports.com/jhm-b5-s4-c5-a6-allroad-2-7t-engine-originally-01e-0a3-6-speed-manual-transmission-conversion-swap-parts-list.html

Fantastic! thanks!