[Anchorman]

It's approaching two years and 45k miles since I had my belts, rollers, and water pump changed. Is it really time for belts again? The car has nearly 130k miles on it. By all visible indicators the car is a-OK (oil consumption - usually about 1/2q in 4k miles; starts easily, pulls smoothly; temperature never above 9:00 position; fuel mileage nearly 23 mpg overall). Last Variocam inspection was 30k miles ago and all looked pretty good. I'm interested in opinions about what service work should be done.

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[BruceWard]

The official interval is 8 years / 60k. If the timing belt breaks you will have down time and greater expense.



Considering the reliability you expect from your 968 I would change it sometime in the next 10K miles and change the variocam chains and pads at the same time. The chain and pads may be ok for now but there is a cost savings to changing them at the same time as the belts.

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[Anchorman]

Thanks, Bruce. I was thinking about adding the chain and pads (I already have the new parts in my tool box). The additional question, then, is whether I'm starting down that "slippery slope". Isn't there a sense that changing chain w/o changing the cams could lead to accelerated wear (although, I must admit, I don't quite follow that logic)? And, if the cams (or at least the sprockets) have to be changed, is there a logic to doing more - such as valves? And, if I've gone that far, considering that the engine will have something like 140k miles on it, should even more be done, like a head?



So that folks understand - I'm not looking to spend money unnecessarily. Whatever work I have done will be done by my OPC, so it'll be pricey. (While I'd love to do the work myself, I simply can't have the car out of commission for the length of time it would take me to do the work.) But, I am planning to keep the car for quite a few more years, and I'm doing about 25k miles per year. That rate of mileage won't continue forever, but it is likely to be in that range for several more years.

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[Bob Kovacs]

[quote name='Anchorman' date='Nov 18 2005, 08:47 AM']Thanks, Bruce.  I was thinking about adding the chain and pads (I already have the new parts in my tool box).  The additional question, then, is whether I'm starting down that "slippery slope".  Isn't there a sense that changing chain w/o changing the cams could lead to accelerated wear (although, I must admit, I don't quite follow that logic)?  And, if the cams (or at least the sprockets) have to be changed, is there a logic to doing more - such as valves?  And, if I've gone that far, considering that the engine will have something like 140k miles on it, should even more be done, like a head?  [right][post="12530"]<{POST_SNAPBACK}>[/post][/right][/quote]

I consider the pads and possibly the chain to be regular maintenance items. However, I wouldn't fuss with the chain sprockets, cams or head/valves unless I knew there was a problem. As long as you have good compression, smooth operation and low oil consumption, don't mess with the head -- as you note, it's a lot of work and there's plenty that could go wrong by forgetting something. If your sprockets' teeth are cracked, damaged, missing or obviously worn, replace the sprocket(s). Otherwise, I'd leave them alone. Ditto for the cam... if it ain't broke, don't fix it.



Some regulars here may be more fanatic about such maintenance than I am but that's my recommendation and I'm stickin' to it.



--Bob

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[sasilverbullet]

my shop says every 30k replace the timing and balance belts...and then re-tension every 10k between changes...

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[Anchorman]

I hear you, Bob, and what you say makes sense. Since there's no indication of problems, don't create them. Definitely makes sense. Sometime before doing this job (probably in the spring), I'll have a compression test done just to confirm the condition of the engine.

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[BruceWard]

Jim,



The theory for changing sprockets at the same time as chains is that the originals will have worn to a matching pattern and that a new chain will increase the wear on the sprockets. Personally I understand the logic but have not seen any evidence to support the theory. I plan to change the chains and pads on my 968 over the winter at 63K miles without changing the cam sprockets. The new chain is less prone to stretching and I believe should cause less wear once it is broken in.



If you did want to have your cams resprocketed you are looking at $600 to $700s and at least a week with them out of the car.



As for the head and valves, once you have the cams off you are close to having the head off. You need to take additional steps of removing the exhaust header and intake manifold, then remove the head. The head will require a new head gasket ($200) when reinstalled. Then you would want to have the head and valves cleaned up. I estimate the head cleanup could be done for as little as $400 by a Porsche trained professional or as much as $1200 by someone like Jon Milledge. Sending the head out is likely to mean 1 - 2 weeks of downtime for your 968.



Have you had your injectors serviced? They will need to come out on the way to the variocam and with overnight shipping both ways can be serviced in as little as three days. Many have reported positive results from injector servicing by http://www.injector.com/ .

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[Anchorman]

Bruce, you've pretty much touched everything I was thinking about - plus reminding me that I've not had the injectors serviced. I think you're right in that I'd be looking at something like a week of work (vs. a complete season if I tried to do this). Sequenced properly with cam exchanges (and head exchange?), a rental car could solve the transportation problem. But - there's the bill at the end. Without having run the numbers at all, I'm feeling that I'd probably be talking about at least $3k, and more likely $4-5k. That's a pretty hefty bite.

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[BruceWard]

If you were to swap parts instead of sending them out for replacement you should be able to get away with the car at your OPC for one day.



You would need purchase a used head, camshafts and injectors.



I think you could get away with a $2000 temporary expenditure and adding about $2000 to what you would spend for changing the belts and chains.

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