By Our Powers Combined? Audi RS4 Frankenstein Project

[Manystylze]

Greetings members and fellow enthusiasts. As the title states, I am seeking those with intricate knowledge to assist in a project that blossomed from an idea when faced with the circumstance of 2 grenades cylinders on a RS4. With a now donor engine aside, and virtually unusable block, I began to search for alternative options for revitalizing my car.

As a disclaimer I know that the B7 RS4 4.2L v8 is closer in detail to the R8 engine, but also noted the differences listed via link:

https://forums.audirevolution.net/t/isnt-the-b7-rs4-motor-the-same-as-the-4-2-in-the-insert-random-audi-4-2-here/3104

The main technical differences between the base engine and the high-revving engine lie in the following:

Crankshaft/connecting rods/pistons
Timing gear
Cylinder head
Oil supply
Engine cooling
Intake path
Exhaust system
Engine management

But started to wonder... I have run across an amazing deal on a 4.2L Q7 FSI engine... so I started to wonder... if the heads on the engines are transferable (i.e. RS4 heads fit Q7 block) as well as the majority of other components, outside the timing gear and engine management, what other exterior concerns would there be? Internally the crankshaft, rods, pistons etc should transfer... and oil pump (will see when I get there). I also know the sunp is different between the 2.

In a nutshell, could the Q7 4.2L FSI block serve as a legitimate basis to replace the RS4 block?

The 4.2 L (4,163 cc) 32v V8 engine of the B7 RS 4 is based on the previous 4.2 L (4,163 cc) all-alloy 40v V8 from the B6 S4, and shares many parts, and Fuel Stratified Injection, with the 4.2 FSI V8 engine in the Q7

[bluebull]

Rs4 = BNS block

What’s the Q have?


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[Protection]

It has been done using the Q7 BAR engine block. I don’t have any details, but recall that holes had to be drilled in the Q7 block for the oil cooler IIRC.

I am about to be in the same boat, as I am replacing the damaged engine in my RS4 with a used BNS. (I broke a piston ring and gouged the wall of a cylinder). If I can find a reasonably priced BAR engine I may disassemble the two side-by-side and see what the differences are.


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[Manystylze]

Rs4 = BNS block

What’s the Q have?


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From my initial understanding the blocks are supposed to be similar with the exception of forged internals for the RS4. I haven't compared part numbers on the block yet to verify. My main concern are the cooling path and alignment on the heads. Going to pull one off and see how the RS4 heads line up.

[Manystylze]

It has been done using the Q7 BAR engine block. I don’t have any details, but recall that holes had to be drilled in the Q7 block for the oil cooler IIRC.

I am about to be in the same boat, as I am replacing the damaged engine in my RS4 with a used BNS. (I broke a piston ring and gouged the wall of a cylinder). If I can find a reasonably priced BAR engine I may disassemble the two side-by-side and see what the differences are.


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Thank you for the info ok n the BAR block. I'll look into it. I dropped a flap in 2 cylinders, 1 repairable but the second did similar damage as yours...gouging the cylinder wall (non-repairable) and one of the heads (a lot of TLC but repairable). Lost both pistons as well.

[Manystylze]

Interested in some feedback. I finally had time to tear down the block and the part numbers on the heads are/were an exact match. I did notice the timing markings and setting were different. I'm sure the cam gears (tooth count) may also be different outside of the timing gears but otherwise an exact fit down to the gaskets.