Audi B5 420-R: The Build

ChrisJC · Post by **ChrisJC** » Mon Nov 26, 2012 8:40 pm

How to make a silk purse out of a sows ear!!

Chris.

Nollywood · Post by **Nollywood** » Thu Nov 29, 2012 5:04 pm

Update 17th November 2012:

I received new OEM Audi S8 exhaust manifolds-to-downpipes retainers, bolts and nuts. I wasn't happy with the old ones. They looked okay, but they are much easier to replace, when the engine's on the bench.

Also, some may recall I decided to junk the stock Audi S8 combined oil cooler and filter, in favour of a remote set-up. This meant having a custom flange machined out of solid aluminium billet. Now the mounting faces were designed to mate to the aluminium V8 engine block with a gasket as the seal. I've thought long and hard about that, and was a bit worried about the integrity. The Audi S8 oil pressure is in excess of 6 bar (87 PSI) at idle when cold. With a healthy engine, that figure will still apply when hot at 2,000 rpm and beyond.

I wasn't keen on seeing how well a thin card gasket would hold up to oil at 90-odd degrees with 6 bar of pressure. The obvious thing to do was use O-rings as the seal. Unfortunately, O-rings can't just be slapped in. Both mating surfaces are flat, so I had grooves machined into the mating face of the aluminium flange, so the O-rings have nice channels to sit in. Perfecto!

Nollywood · Post by **Nollywood** » Thu Nov 29, 2012 5:14 pm

New OEM Audi S8 exhaust manifold-to-downpipe retaining nuts, bolts and retainers:

Audi S8 exhaust manifolds, with the old rusty bolts and retainers:

Now fitted with new bolts, nuts and retainers:

Nollywood · Post by **Nollywood** » Fri Nov 30, 2012 12:26 am

Here's the custom-machined flange, as I had it made originally. Note the lack of O-ring grooves:

And machined, to accept two large O-rings:

With O-rings fitted:

ChrisJC · Post by **ChrisJC** » Fri Nov 30, 2012 8:34 pm

Nice machining. How do you know how deep to make the groove?

Chris.

Nollywood · Post by **Nollywood** » Sat Dec 01, 2012 12:44 am

ChrisJC wrote:Nice machining. How do you know how deep to make the groove?

Chris.

Thanks buddy. I can't take the credit though. There's a Data Sheet with different O-ring spec, and how deep the grooves need to be made.

This was done in a shop, all I did was give them spec, they worked out the rest.

Mark · Post by **Mark** » Sat Dec 01, 2012 8:28 pm

Great project

I assume you have to fabricate engine mounts to get the V8 in the B5 chassis ?

Nollywood · Post by **Nollywood** » Sat Dec 01, 2012 11:31 pm

Mark wrote:Great project

I assume you have to fabricate engine mounts to get the V8 in the B5 chassis ?

Yes, custom mounts. If it were a 40V from an Audi A6 / S6 (C5 chassis) it'll bolt straight in.

But, I've always preferred the 32V motor.

Nollywood · Post by **Nollywood** » Thu Dec 06, 2012 8:45 pm

Update 06th December 2012:

I received my spot-weld drill bits in the post today, so the secondary firewall has been removed. I ordered 6 and 8mm bits, as I wasn't 100% sure what size the Audi secondary firewall spot-welds were. I planned to go with 6, then move up to 8mm, but in the end, the 6mm bits did the job perfect.

I'm now left with a hollow box section, which I'm going to plate over with aluminium. I've made a cardboard template. Once she recess is covered, I'm going to steam clean the entire engine bay, degrease it thoroughly, then prep it for paint. Just rub down, primer then 2 final coats of satin or gloss black. Then the 4,2 V8 engine and 01E 6-speed manual tranny can be installed. With the secondary firewall removed, there's loads of room for a big snail to fit at the rear of the engine.

I removed the original heat shielding, which will be replaced once the bay is painted. Some pictures:

Spot welds drilled through in secondary firewall:

Secondary firewall being pulled off:

Secondary firewall removed:

Secondary firewall. Note the VIN stamped into the sheet metal, and riveted tag. These will be transferred to the new locations:

Cardboard template that forms the basis for the aluminium plate that will cover the hollow recess:

topcatcustom · Post by **topcatcustom** » Mon Dec 10, 2012 11:59 am

Just a thought- would you not be best using thin steel instead of aluminium, and spot welding it to the face much like the original? That way it will be slightly more rigid- and may reduce any flex as it looks like that cross member ties the front turrets together. Weight difference will not be worth considering as it's only a small piece!

kiwicar · Post by **kiwicar** » Mon Dec 10, 2012 1:49 pm

Hi Looking at this in the light of what Tom has just pointed out I would have a bit of a review of the whole area, when the bonnet is closed the upper half of that pannel forms a box section with the underside of the bonnet with it closed. If you look at the underside of the bonnet there is an internal panel that has a lip folded to the rear, the panel has a lip turned forward, I bet in a prang to the front of the car that pushes the bonnet backward the pannels are intended to lock together. . .I would certainly satisfy myself that this was not the case before I proceeded any further

. It looks a bit like the old chestnut of removing the rear pockets out of a Mini! (once you had the first big bump you came to you ended up with the rear sub frame in the the passanger compartment with you!

).
I think it would be wise to get an engineers report on what you have just done and on what you plan to replace this with, it looks very structural I would certainly consider carefully how you are giong to put back the strength into that area.
As regards the VIN plate, it should have a duplicate on the chassis somewhere, I would make sure it can be accessed quickly.
Best regards
Mike

r2d2hp · Post by **r2d2hp** » Mon Dec 10, 2012 2:22 pm

Could you not just use the cardboard template and mark on the piece you have removed. Cut it outs and spot weld back in and add the vin into it at the same time

chodjinn · Post by **chodjinn** » Mon Dec 10, 2012 2:42 pm

I don't get why you have removed it, doesn't look like you've gained any room at all looking at the position of the spot welds?

kiwicar · Post by **kiwicar** » Mon Dec 10, 2012 4:23 pm

The more I look at this the more it looks a very bad idea! as a general rule VIN numbers are put on bits of chassis that the car cannot easily do without, the idea is to make it difficult and expensive to change the identity of a car by cutting out the VIN number from one car and transfering it to another. By implication if it has the VIN number on it a panel is required.

Best regards
Mike

bmwcapri · Post by **bmwcapri** » Mon Dec 10, 2012 5:35 pm

Could you not just use the cardboard template and mark on the piece you have removed. Cut it out and spot weld back in and add the vin into it at the same time

Looks like you'll be needing an IVA test then...
(just kidding!

) Great project btw, keep up the good work