Types of VR Timing Chain

[Philstrm250 10]

Hi all,

 

I'm trying to find out what type of upper and lower timing chains were originally fitted to 2.9 VR engines and if there are any differences or variations? I was under the impression that all 2.9's have a Simplex single width lower chain and a Duplex double width upper chain, although some forum members have said they've seen Simplex upper chains on a 2.9 VR.

 

Taking this a step further, does anyone know how the chains vary from an early 2.8. AAA or 2.9 ABV engine, through to late 2.9 or Mk3 Golf 2.8's?

 

I've also heard that late VR 2.8 engines had 2x Simplex chains, post Corrado, maybe from '97 onwards, due to wear issues with the Duplex system / guides / tensioners.

 

Cheers

[dr_mat 0]

I think there's two separate things here, almost unrelated: one is the single or double chain top end, the other is the type of tensioner. As far as I'm aware all early VR6's had the teflon-and-rivets tensioner pad which was later shown to be unreliable, so later engines (after the Corrado was pensioned off) got the newer all-plastic solid tensioner pad.

Independently of this I remember someone saying that the Corrado got a double upper chain to deal with the extra power it was supposed to produce when compared with the AAA 2.8. Don't know how true this is.

I also heard a rumour that the Corrado may have got a 2.9 because they had a load of rebored 2.8s sitting around and they didn't really know what to do with them.. I'm sure *that* is just a rumour though.

No doubt there's others who have more details ..

[Philstrm250 10]

Many thanks dr_mat for the info.

My Storm's engine had the chains replaced by the previous owner but it appears to have a Simplex upper chain which is weird.

So maybe some of the late Corrado VR's had 2x Simplex chains fitted from new, I need to check my bore diameters or the head gasket to confirm if it's a 2.9, is it 82.5mm for the 2.9 or 81.5mm for the 2.8?

My head gasket's currently being replaced and my head serviced and refurbished when this issue came to light, the new genuine 2.9 HG fitted just fine.

I've got no indication from the previous owner or the service history that my engine's been replaced.

[Stonejag 10]

Have you got a big triangular hole in your cylinder head next to / below the camshaft gears? If so you have an AAA head which should have a simplex upper. Don't think it really makes much difference tbh :)

[Roger Blassberg 0]

I don't think the simplex/duplex change was anything to do with engine power; the chains drive the valve gear so there is no direct correlation with horsepower, only with valve gear resistance (spring rates and camshaft profiles) and engine speed so perhaps an indirect influence. My understanding was that all ABV engines had a duplex top chain with the rivetted tensioner blade, all AAA had simplex with the later ones getting the solid pad and an improved hydraulic tensioner. A change from duplex to simplex top chain would presumably need different intermediate and camshaft sprockets if you'll excuse a statement of the bl££din' obvious.

 

Best wishes

 

RB

[dr_mat 0]

Yeah, suspect your single upper chain is not original. I've never heard of an unmolested Corrado VR6 getting anything other than the old twin-chain upper setup. And Roger yes I agree, there doesn't seem to be much logic there. Perhaps there was a feeling that two chains was likely to be more reliable? I think the old 16v heads used a pair of chains to connect the two camshafts? Maybe they still didn't have the confidence to move to a single chain until later on.

[Roger Blassberg 0]

Yes, certainly the ABF uses a duplex transfer chain and it only drives one of the camshafts, albeit with 8 double springs to compress at quite high revs.

 

RB

Edited July 12, 2013 by Roger Blassberg

[Timbo 0]

On the same(ish) subject; is there a good place to get a timing chain replacement kit right now? Getting all the bits through the dealer sounds like wallet rape waiting to happen.

[GlosterOx 0]

On the same(ish) subject; is there a good place to get a timing chain replacement kit right now? Getting all the bits through the dealer sounds like wallet rape waiting to happen.

 

Four Seasons in the States list one, but not sure how competitively priced it would be with the current exchange rate and delivery etc: http://www.fourseasontuning.com/index.php?product=14&product_code=dualupperchainkit

 

Ian.

[nrc 0]

I got Febi chains and the rest (tensioners, pads, etc) from TPS. All fine so far.

[Philstrm250 10]

Many thanks for the advice guys.

I will check my bore sizes, what should they be?:

AAA 2.8: 81.0mm or 81.5mm, piston stroke 90.0mm

ABV 2.9: 82.0mm or 82.5mm, piston stroke 90.0mm

 

So it would seem then that all 2.9 ABV engines should have a Duplex upper and Simplex lower chain fitted from new and that late 2.8 AAA from 97/98 onwards had a Simplex top chain.

 

Cheers

[Philstrm250 10]

Does anyone know for certain what the bore sizes are in mm for a 2.8 and 2.9 VR6 please?

What does the Bentley manual say for the 2.8 and does it show a diagram of a Simplex top chain? if anyone's got a copy of their manual handy.