Confused

[radzoule]

The timing chain on my 98 4.0 is a duplex chain. I thought (per the bible) that the standard chain on these cars was a single chain? I'm now away from the vehicle so can't check, but the engine builder at RPI engineering thought this meant it would also have vernier adjustment, and so the chain shouldn't be removed "at home" for fear of getting the timing right on replacement. He also said that these chains do show a fair amount of slack (the reason why I thought it might need replacing).

The car has only done 45,000 miles so I can't believe that this is an aftermarket replacement. Anyone have any ideas?!

If I decide to change the cam, can the cam/chain be changed at home with a little care, or is RPI correct that this is beyond the home mechanic. I have changed non vernier gear before. I'm planning to get a tornado chip and Mark Adams remap when I put the car back together and would be interested in upgrading the cam now whilst everything is apart. A search on these forums seems to suggest that a hybrid 218 is a good upgrade, but will this impair driveability?

[GreenV8S]

I agree with you. The standard timing chain is a single chain. The aftermarket cams usually use duplex chains with a vernier adjuster.

You can take the cam chain off without disturbing the vernier adjuster, but if the cam needs replacing it is pretty safe to assume that the drive will need replacing too. If you replace the drive then you will need to set the cam timing using the vernier adjuster.

[David H]

If you are reasonably competant with the spanners and have the right tools then you will able to set a vernier up no probs.

If you go for a 218 hybrid from V8 it may be better to time it in as per their suggestion. A H404 will impare drivability on a 4litre i'm sure. Probably best you speak to them direct to give them a better understanding of what you want.

>> Edited by David H on Tuesday 3rd January 19:18

[Bomber Denton]

I thought the 500 has a Duplex as standard?

[David H]

Bomber Denton said:

I thought the 500 has a Duplex as standard?

He has a 400 though

[victormeldrew]

Bomber Denton said:

I thought the 500 has a Duplex as standard?

It does, a vernier duplex.

[Tobs]

Doesn't the 400HC have a duplex?

[radzoule]

I think mine's a bit late to be an HC (98 S plate). I wonder whether a previous owner had a TVR Power upgrade done at some point though? That might explain why she's always been a bit quicker than I thought she should be

Seriously though, after a couple of run-ins against a new XKR (beat) a new Maserati (he only just had an edge) and a Carrera (again he only just had an edge) I said to my flatmate a couple of weeks ago, "you know, that car really isn't that slow, despite being the baby"!

[v8 racing]

Without going down the route of the hc not a hc road again trust me yours is an hc!!! all tivs from around 95 were hc's! the main reason the chain has stretched so much is due to the spring pressures of the valve springs to be honest a very common problem, its not that important for performance issues as when you time a cam in you always turn the engine over to make the chain tight and not on the slack side, problems become when they are so slack they can jump a tooth, it sounds very complicated to time a cam in but the reality is quite easy but you will need a dti gauge to measure lift, if you fancy doing it yourself i am happy to talk you through it
Rob

[radzoule]

Thanks Rob - I'm going to visually inspect the cam in situ, and if it looks worn I'll pull the whole lot and give you a call, unless you travel Can you recommend any particular dti guage? Will I also need a dial guage to check TDC of no 1 piston?

[v8 racing]

yes rad you will need a dial gauge dont go and buy one though i litterally have hundreads here if you want one