S6 vs A8 4.2 V8 - Engine differences?

[Dan95x]

Morning all,

Following my introductory post a week or so ago, the good news is that when the cambelt tensioner went in my S6, it doesn't appear to have done any valve/piston damage - hooray!

However, it is knocking from the bottom end - booooooo. Garage reckon it sounds like a conrod bearing knackered - great!

How similar are the 4.2 V8s in the S6 and the A8 4.2V8, does anyone know? I know that the A8 version only makes 300bhp, I am guessing that this is probably cams and map that make the difference, so the bottom ends are the same possibly?

(I think you can see where my thinking is possibly heading!)

Cheers in advance

Dan

[bam_bam]

What year is yours?

They should be the same (even power outputs), there was never a 300bhp unit for the S8, they should be either 335bhp or 355bhp.

C5 S6 (AQJ: 09/99-05/01), D2 S8 (AHC: 09/96-12/98, AKH: 08/97-12/98, AQH: 05/99-02/01, AVP: 09/00-09/02).

It looks like the AHC/AKH from the earlier D2 S8 is the same as the AQJ in the S6 (335bhp). The AQH/AVP/AYS/BCS in the later S8s were 355bhp.

You'll find all of this in ETKA, that should also tell you the crank info.

[Dan95x]

Cheers dude, but I meant the A8 with the 300bhp V8, rather than the S8 (in that a 4.2 A8 is virtually worthless to buy, whereas an S8 still holds its price reasonably well) - One has come up for sale locally to me for cheap enough that if the bottom ends are the same, it would be worth me buying the A8, breaking it to keep the bottom end for swapping into my S and possibly coming out of it expenditure neutral (but having lost a few weekends!)

My other option of course is to pull the S apart, locate the conrod bearing that is gone and replace that. I am thinking probably the oil pump is not working properly, as otherwise (unless this is a massive problem on these engines and I am guessing wrong) it seems a strange problem to occur on a relatively low-stressed engine.

The issue with that is that I could just end up throwing money at it when it could have caused all sorts of other problems etc etc, and I may still end up having to source another engine anyway!



Dan

[Mr Footlong]

Confused, there is an active S6 discussion section on this forum - http://forum.rs246.com/viewforum.php?f=44

[Dan95x]

I wouldn't describe it as 'active'!

I will happily sod off if anyone doesn't want me on the RS section, it just seemed as if there was a bit of an unspoken rule that it was ok for us poverty stricken, turbo missing peasants to post on here as you might actually ever get a reply!

[Mr Footlong]

Sorry you can't afford a pair of tubbys chap . I like things tidy and in relevant sections when I read a forum, reading stuff that is technically for 2 or 3 different forums makes my eye twitch

I have pissed you off so my work here is done, helpful types will no doubt continue to spam info for you if there is info to be spammed.


Edit, typo...

[Dan95x]

Sorry you can't afford a pair of tubbys chap . I like things tidy and in relevant when I read a forum, reading stuff that is technically for 2 or 3 different forums makes my eye twitch

I have pissed you off so my work here is done, helpful types will no doubt continue to spam info for you if there is info to be spammed.

Ha ha - Not a problem as far as I am concerned - Being a newbie it is far more your lots forum than mine, and I will play however you all play. I agree with you, much easier to keep everything where it should be, just seems that the C5 S6 sub forum is quieter than a nuns knickers.

I also wish I could afford a couple of tubbys - At the minute I would settle for just a car that is working and not causing me arseache

[Mr Footlong]

There may well be some like me that rarely venture out of this part of the forum so casting you net in the S6/A8/general Audi sections, with a link to this thread may help you greatly. I have seen others do it so spam away chap.

[bam_bam]

Cheers dude, but I meant the A8 with the 300bhp V8, rather than the S8 (in that a 4.2 A8 is virtually worthless to buy, whereas an S8 still holds its price reasonably well) - One has come up for sale locally to me for cheap enough that if the bottom ends are the same, it would be worth me buying the A8, breaking it to keep the bottom end for swapping into my S and possibly coming out of it expenditure neutral (but having lost a few weekends!)

My other option of course is to pull the S apart, locate the conrod bearing that is gone and replace that. I am thinking probably the oil pump is not working properly, as otherwise (unless this is a massive problem on these engines and I am guessing wrong) it seems a strange problem to occur on a relatively low-stressed engine.

The issue with that is that I could just end up throwing money at it when it could have caused all sorts of other problems etc etc, and I may still end up having to source another engine anyway!



Dan

Ahhhh, the 32valve! I cannot see that being the same.

/EDIT That said, there's nothing in ETKA that would say otherwise. You could be right. Problem is, if you were to swap out the crank, wouldn't you want a new(er) one?

[Dan95x]

Yeah - I have just had a bit more of a look, it doesn't look like it is. I think it was just wishful thinking induced by panic to be honest.

My own fault for tricking myself into thinking I could run such a car on a budget - It was nice for half an hour or so while it lasted.

I will go cry in the corner and go back to poverty spec four pot motors........

Anyone want to buy a none-running (well running but not well) 51 plate S6 - No-one? No didn't think so............

[Shoppinit]

Unfortunate failure. Those engines are normally good for starship miles. You sure of the diagnostic? Might be worth getting a second opinion.

[Mr Footlong]

Me being lazy/busy but what sort of monies do these non-tubbys go for? I have been toying with buying one for the folks as my dad won't shut up about wanting one every time that he taxis me to hospital in mine. I did the same with the Jag though and they wouldn't take it from me due to the fuel cost....

[Shoppinit]

I thought the A6 4.2 block was the same as the S6 block. Just the air tumbler device and other little mods giving the extra 30 odd hp.

You might be better off posting this question in general car chat. Lots of people on this site that know lots about Audi engines that don't necessarily look in this forum.

[Dan95x]

Unfortunate failure. Those engines are normally good for starship miles. You sure of the diagnostic? Might be worth getting a second opinion.

Not 100%, but as he said, will cost me a fortune in labour for him to tear into it to confirm - I will do so myself when I get it back on the drive. All crap timing, as normally it wouldn't be a massive issue, but I am currently without car, live in the Midlands but work in Cardiff, and have very little space to play with for car storage, and very little time to sort anything out at the minute

It does now have a spanking fresh cambelt, tensioners, idlers, waterpump, thermostat and fresh coolant though I suppose!

[Dan95x]

Me being lazy/busy but what sort of monies do these non-tubbys go for? I have been toying with buying one for the folks as my dad won't shut up about wanting one every time that he taxis me to hospital in mine. I did the same with the Jag though and they wouldn't take it from me due to the fuel cost....

Reasonable mileage one with decent history seems to be starting from £3500-£4000 - Lower mileage ones a bit more. If they didn't like the fuel cost on a jag though, I cant imagine they would go for one of these either!