Cam shaft change

Toms968CS · Jan 27, 2011

As my car has 80k on the clock and I haven't got any proof that the Cams and Variocam chain have been changed I think it's probably best that it's done now - before I start charging round tracks and finding out how expensive replacement engines are!

My questions are:

Is the cam change DIY-able, in that are there any weird (expensive) tools I need to undo gibberty-flibbit nuts and are the parts easily available? Or, is it best to take the car to someone who has done it many times before and save myself a whole load of grief (swearing and busted knuckles).

Secondly, where would people suggest in the W Midlands area to carry out this work, and roughly how much should it cost?

Thanks

Tom

Paul RN · Jan 27, 2011

www.emcmotorsport.co.uk

Big Dave · Jan 27, 2011

I second the EMC chaps....
But you might not need a set of cams, although that could be worst case .
Get them looked at [EMC],+ poss just get the cam chain replaced along with the chain slippers.

964RS_DAB · Jan 28, 2011

+1 for EMC, they're local to you aswell Tom which is a bonus. Kevin is very fair, he won't change things for the sake of it

My 968CS had the camshaft changed at 78k together with chains and ancillaries, it cost around £3k. Interestingly only the inlet cam was changed - apparently it's the inlet cam that is most prone to excessive wear. I've got my original inlet cam mounted on a piece on marble in the lounge, which is always a talking point amongst friends when they visit [

]. There are about 6 teeth missing from the original camshaft, hopefully the remains of those teeth are no longer in the sump [&:]

Toms968CS · Jan 28, 2011

Thanks for the info. I have purchased the necessary gaskets from Solihull OPC so at least I can have a check myself as I found a "how to" guide on the web.
All I need now is a slab of marble.......

dparslow · Feb 7, 2011

I did a top end rebuild on my car last year, it didn`t need the cams as it had new ones at 60k, but some pics here:

https://picasaweb.google.com/marcosman46/Porsche968TopEndRebuild082010?feat=directlink

sawood12 · Feb 7, 2011

Are you looking to replace the cam chain or cam shafts? I can't imagine the cam chain change is any more complicated than a cam belt change - a cam shaft change is a different prospect altogether - not that i'm suggesting you are not capable, but if you're going to the trouble of changing your camshafts you might as well effectively refurbish the head while you've got it disassembled. I'd be surprised if your camshafts have had it and require replacement after only 80k miles.

rcsalmons · Feb 7, 2011

ORIGINAL: sawood12

Are you looking to replace the cam chain or cam shafts? I can't imagine the cam chain change is any more complicated than a cam belt change - a cam shaft change is a different prospect altogether - not that i'm suggesting you are not capable, but if you're going to the trouble of changing your camshafts you might as well effectively refurbish the head while you've got it disassembled. I'd be surprised if your camshafts have had it and require replacement after only 80k miles.

Not quite right - cams need to come out to change the chain much more involved than belts and yes plenty of 968's have had their cams changed around the 80k miles mark.

Rich

Neil Haughey · Feb 8, 2011

ISTR there was a bad batch in the early years, something to do with poor case hardening or something leading to them literally wearing out, not just the teeth that the chain sits on.

My 92 car had new cams a long time ago, would have been less than 100K miles but was a good 10 years ago now. The bill was a frankly shocking £3.2K almost half of which was the cost of the cams alone, the rest was a full head rebuild. AFAIK some of the late S2's also suffered this problem, I am fairly sure Fen was one of the guys who experienced this, ISTR in his S2 cab.

frogisland · Feb 8, 2011

..and the later cars Neil. The case hardening went on one of my cams - lobes were buggered as were some of the cam followers!

Might take a picture, they're still sitting on the garage floor! Have one good cam if it is worth anything to anyone....

JP

Neil Haughey · Feb 8, 2011

Its still after all these years a bit of a mystery then as to why this happened on various cam batches in the 90s. My S2 engine is still on its original cams at 171K miles, EMC reckon its the most powerful stock S2 engine they have ever seen (made 227 Bhp on the rollers last autumn but was a bit top endy, terrible shame I didn't get to show its new found awesome power before she decided to only use 3 cylinders [

]). ISTR Paul Smith's S2 is similar at getting on for 200K miles all on original engine hardware.

Fraser · Feb 9, 2011

A timely thread this, as I'm getting cams, chain and belt change priced at the moment.....

Thanks for the thread and the comments.

JM1962 · Feb 10, 2011

Great pics there Dave. Looks like theres plenty of room to work on the front of the engine once the airbox and radiator have been removed.

paulf968 · Feb 11, 2011

I think I am right in saying that the later cams had their teeth slightly reprofiled to make them less susceptible to breaking off.

The only other thing I would add is that a proper 'engineering assessment' of the cams and chain etc is needed before diving in and changing things for changes sake. For example my experience at a well known indie was that the chains were carefully measured and cam lobes also measured using a vernier caliper and dummy rollers in the lobes. This indie was then able to predict based on many years of records what would last say 20k or 40k more miles. Then an informed decision can be made on what to change. NB just don't want any of you wasting money.

ps also remember that not removing the head to check the gasket and the water pump may be a false economy - you saw the earlier thread on this I am sure!

Toms968CS · Feb 13, 2011

Many thanks for all the comments (and pictures). I've had the cam cover off today and had a good look - the only thing that looks a problem are the chain runner pads which are dark brown. There's no teeth missing from either cam (phew!), all I need to do is contact EMC and get it booked in - I'll also get them to do the head gasket at the same time.

sawood12 · Feb 15, 2011

ORIGINAL: rcsalmons

ORIGINAL: sawood12

Are you looking to replace the cam chain or cam shafts? I can't imagine the cam chain change is any more complicated than a cam belt change - a cam shaft change is a different prospect altogether - not that i'm suggesting you are not capable, but if you're going to the trouble of changing your camshafts you might as well effectively refurbish the head while you've got it disassembled. I'd be surprised if your camshafts have had it and require replacement after only 80k miles.

Click to expand...

Not quite right - cams need to come out to change the chain much more involved than belts and yes plenty of 968's have had their cams changed around the 80k miles mark.

Rich

Really? And I thought the whole point of chains is they are effectively fit and forget unlike belts. I assume that you can't simply take a link out, drop the chain off the sprockets and pull it out? I guess there is not enough clearance. Anyhow, I wouldn't imagine it is a good idea to replace the chain and not the sprockets/cams. Chains tend to wear into sprockets so if you change the chain the difference in diameter between the new chain link and the worn sprocket profile can cause the chain link the sit on two points or one single point rather than contacting around the whole profile of the sprocket valley. This can cause increased stresses in both the chain link and the sprocket tooth leading to failure of one or the other. This is probably why there is no service interval on S2 and 968 cam chains as it implies cam replacements too. Not sure if this is an issue on these things.

Big Dave · Feb 15, 2011

Scott.
PLEASE dont take this as me "having a go" or being condescending.
BUT...
If you havnt heard about the 944/968 twin cam cam chain + camshft problems, then where have you been.[8|][8|][8|]
I know of LOTS and LOTS of these engines that have needed new chains + cams , generally at or around 70K miles mark. I know Porsche never made it a servicable item, but they shouldve done.
I know also of a lot of people who have been caught out through buying a supposedly good car around 70-100K mark and almost imeadiately have had to replace the cams and chain.
If i ever see anybody asking for buying advice i try and "warn" them about this very point.
They [the chain,s] NEED checking and or replacing around 60-70K mark...If left any longer then your looking at new cams..£££££££££££££££

vitesse · Feb 16, 2011

Scott,
The chain doesn't drive by fitting in the "valley " of the sprocket as you mention,but by a line contact between the chain roller & the sprocket tooth at a point along the flank of the tooth ranging from the theoretical PCD to a higher point as the chains & sprocket wear.
Normal wear limit for a drive with normal centres is 2% but the cam to cam drive on these engines is very short & there are few chainlinks to share out the wear resulting from the chain load-also the sprocket teeth nos are also low which exacerbates the wear factor.
By replacing the chain earlier than later,reduces the chance of having to replace the cams as well-they should last 3 chains at least.

sawood12 · Feb 17, 2011

ORIGINAL: Big Dave

Scott.
PLEASE dont take this as me "having a go" or being condescending.
BUT...
If you havnt heard about the 944/968 twin cam cam chain + camshft problems, then where have you been.[8|][8|][8|]
I know of LOTS and LOTS of these engines that have needed new chains + cams , generally at or around 70K miles mark. I know Porsche never made it a servicable item, but they shouldve done.
I know also of a lot of people who have been caught out through buying a supposedly good car around 70-100K mark and almost imeadiately have had to replace the cams and chain.
If i ever see anybody asking for buying advice i try and "warn" them about this very point.
They [the chain,s] NEED checking and or replacing around 60-70K mark...If left any longer then your looking at new cams..£££££££££££££££

Dave, not taken i the wrong way at all, i'm genuinely interested and just trying to understand what the issue is for my own interest/knowledge. Of course I had heard of the odd issue with cam lobe cracking and sprocket teeth breaking off with the S2's over on the 944 forum, but I hadn't got the impression that it was so prevalent and for most S2 owners it doesn't even seem to be a consideration - only the chain tensioner and slipper pads. Maybe it is a manufacturing issue that it must affect 968's more.

rcsalmons · Feb 17, 2011

ORIGINAL: sawood12

ORIGINAL: Big Dave

Scott.
PLEASE dont take this as me "having a go" or being condescending.
BUT...
If you havnt heard about the 944/968 twin cam cam chain + camshft problems, then where have you been.[8|][8|][8|]
I know of LOTS and LOTS of these engines that have needed new chains + cams , generally at or around 70K miles mark. I know Porsche never made it a servicable item, but they shouldve done.
I know also of a lot of people who have been caught out through buying a supposedly good car around 70-100K mark and almost imeadiately have had to replace the cams and chain.
If i ever see anybody asking for buying advice i try and "warn" them about this very point.
They [the chain,s] NEED checking and or replacing around 60-70K mark...If left any longer then your looking at new cams..£££££££££££££££

Click to expand...

Dave, not taken i the wrong way at all, i'm genuinely interested and just trying to understand what the issue is for my own interest/knowledge. Of course I had heard of the odd issue with cam lobe cracking and sprocket teeth breaking off with the S2's over on the 944 forum, but I hadn't got the impression that it was so prevalent and for most S2 owners it doesn't even seem to be a consideration - only the chain tensioner and slipper pads. Maybe it is a manufacturing issue that it must affect 968's more.