20V CQ Tidy Up

[Error404]

Found some time to do a bit more work on the engine today.

I ended up ordering ARP head and main studs from 034, which turned up a week or so ago.
I was originally planning to run with OEM main bolts, but I thought what the hell, I've started down this road now, best pull out all the stops

So I started by cleaning the bolt holes out with carb cleaner and an airline, and they checked that all the studs went in nice and easy by hand with no resistance.





Then I checked the main tunnels for size by torquing the ARPs down and measuring in 3 planes with an inside micrometer:



Previously they had measured up on spec with the OEM main bolts. Now the the extra clamping load of the ARPs they appear to be about .02mm out of round - they are squashed. So I will get this double checked by the machine shop with a more accurate bore gauge, but it looks like it will be necessary to get them align honed to bring them back to round. At least that means I can make sure they are all on bottom size.

Whilst I was doing that I also fitted the new KS shells to check the crush height. Not enough crush is the biggest reason for spun bearings and the big end bearing failure that quickly follows. All mine have a healthy .125mm which is perfect. With all the tunnels on bottom size, crush is maximised so this will only improve if the mains get honed.




Then I modified the windage tray to clear the studs:




The compression ratio issue has been rattling round my brain for a couple of weeks now, so I did some measurements and calcs to work out exactly what I would get with the Wossners - as it turns out, not quite what Wossner quote

Calculation spreadsheet is attached (let me know if you spot any errors )

Crude technique to check the Wossner piston dish CCs - I made 12.0cc so their spec looks right:



So assuming zero piston deck height, the CR is 8.0:1
However the compression height on the Wossner pistons is 33.50mm vs 32.80mm for the OEM pistons, therefore giving an above deck height of 0.70mm.

Feeding that into the equation gives a compression ratio of 8.5:1 - perfect.
So that has set my mind at rest.


I also bolted up the 0A3 gearbox to an old 7A block I had kept and test fitted the B6 S4 linkage which I am going to try and use. It is a better design IMHO than the S2/RS2 linakge and the later 0A3s shift like warm butter. Easy to see why our cars are nose heavy



That's it for now

[andy10v]

Lots of interesting stuff as usual!

[irishs2]

Very nice info.

Will the b5 gear linkage fit without much effort or will modification be required to the car/linkage?

[Error404]

Its a B6 linkage, but I think its pretty similar to a B5 one.
I think the shift rod and stabiliser will need shortening slightly, and possibly some slight mods to the mounting plate on the tunnel - not sure just yet but will post up more info in due course.

I'm probably going to start stripping the car down in the next week or two as I have a fair bit to do on it if I want to make it to ADI!

[Acidburn]

yeah from what I remember when I looked into it, its the length of the shifter thats different. I think the cradle even bolts in to place correctly, you just need to do two new holes at the rear from what I remember. been a while since I tried it tho.

[irishs2]

Appologies B6 is what i ment.

[Pat D]

Neat work there I'll hopefully attempt to do this work myself on the next build.

Are you going to measure and take in to account piston rock, or tilt? I was told by a few, and learnt after some reading that this should be considered when calculating piston to head clearances as piston rock will occur, and more so on a cold engine.

I worked out my total piston height and added piston rock on top of that to give me the absolute piston height. Piston tilt was measured at 0.1903mm when tilting upwards on one side with my build, so I added that to my piston height and aimed to not exceed .91mm piston to head clearance.

[Error404]

Hi Pat, I hadn't factored in piston rock to be honest, as the Wossners run pretty tight bore clearances compared to say JEs so I didn't think it would be a very significant. From what I have read minimum piston to head clearance should really be 1.0mm to allow for some carbon buildup and rod stretch, so I am border line at that. I will measure it when I do the dummy buildup, but I am confident it will be fine

[Thuppu]

Lots of interesting stuff as usual!

[diesel des]

I was aiming for just under 1 mm clearance on my build, no less than 0.850 mm with piston in bore with no rings and full over to one side. Getting no more than 1mm is ment to be a magic number. Dangerous game though...

Stroker with wossner pistons.

Sent from my GT-N7105 using Tapatalk 2

[Error404]

Yes the squish / quench clearance was supposedly the big secret way back when
I think probably more important with an NA motor, but still I think all these small things do add up to make a difference. The difference between throwing some new rings and shells into a build or taking the time to blue print it.

[Fat Audi 80]

Nice work.

[Error404]

The block is off at the machine shop at the moment, getting bored & decked. The called today to tell me that the mains need some attention. As I suspected they were 0.030mm out of round due to the extra clamping load from the ARP studs. They need to plane the main caps and then align bore and hone the mains to get them back to being round, so I'm expecting a chunky bill for that. I know a lot of people just chuck ARP main studs straight in, and I'm sure that is fine but I'm not taking any chances as I want this engine to be bullet proof - perfect bearing bores is a good way to start.

In the mean time I have started stripping the car down, as I realised I have a lot of work to do! Engine and gearbox is out:



Engine, fan, lighting and alternator looms are out as I will be using ABY harnesses for these.



Its been a good opportunity to tidy up the wiring for all the extras I have added over the years, and also to repair all the old dry and flaky loom tape which was a complete mess. I found it easiest to pull the fuse board down into the cabin and unscrew the aux relay panel so it was all there to get at.
Damb the wiring is a mess on these cars! The dash harness is about a foot too long which doesn't help space down there!

Once this is done I can install the cabin side of the ABY harnesses and then patch in the digital climate control harness I already have made - I really want to make it "plug & play" using connectors already available, but time will tell if this is feasible or not since digital climate was not an option at all when my car was made in 1989.

I'm also hoping to start work on fitting the 0A3 gearbox soon - custom mounts and getting the linkage to work.

[Christophski]

You don't like making life easy for yourself do you Alex? lol. This is gonna be the highest comfort coupe out there on e done haha

[irishs2]

It's looking quite serious now !

I see the brake servo loose, are you thinking of switching to vacuum ?