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Ticking noise to Rebuild time - worst 50 Miles ever.

Nightmare.

Bad luck especially since the engine has already been rebuilt once.

Your guy is probably talking about liners by Capricorn then?
 
MisterCorn said:
I think it is largely irrelevant who did the previous work, unless it is thought that the failure was caused by some debris they left in. I'd be interested to see photos of the bearings though. We know that they wear and around 100k can be rebuild territory depending on usage patterns.

MC
I was interested to find out which make/version of liners had failed so the same ones didn't go back in. On further research there is now some confusion on whether it was strengthening work on the bores. Not quite sure what strengthen work means in relation too closed deck design?. Anybody care to enlighten me.
 
Probably support rings. If the bores were still within tolerance for roundness then support rings around the top of the bores would have been an option. They aim to stop ovality at a later date.
Not as thorough a solution as re-sleeving. Cheaper though.
 
thanks- that makes sense as there is slightly different metal colouring at the top of bores 4&5.
 
I've taken pictures to help explain but can't easily upload them – I can email them to someone to upload if there are any volunteers, otherwise similar pictures can be found on our website www.hartech.org

The normal potential problems with the cylinder design are scoring/scuffing & cracking.

Scoring isn't as common in the 996 3.4 engine as the 3.6, 3.8 & 3.4 987 models but it can still happen, particularly with the Ferroprint pistons.

There are numerous contributory factors with scoring but the underlying issue is that the cylinder bore running face (Lokasil) isn't quite up to the job in many cases. This is why we choose to go with Nickel Ceramic plating (like in the Metzger engine) as a running surface which is much more durable – it is electro plated onto an aluminium alloy wet liner which shares the same expansion and contraction rates as the rest of the block so is nice and stable in both the deck height and integrity of fit rather than a different material with half the expansion and contraction rate.

Cylinder cracking is a totally different issue and comes about because the original design is essentially a tube of metal just surrounded by water without any support at the top. The thrust loading over the years pushes against one portion of the cylinder and it gradually goes oval and eventually cracks. Our new cylinders are a 'top hat" design so naturally stronger and are locked against the casting in a precision machined diameter - so cannot move so will not migrate oval and crack. The original design is an 'open deck" whereas the wedging of our liner against the other part of the block makes it more of a 'closed deck". (Incidentally, this isn't a classic problem with the smaller engines as the cylinder walls are thicker & stronger).

The 'closed deck" element of our liner can be re-produced by infilling the space with a support ring of metal.

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as 'closed deck". They are NOT liners nor Nikasil plated. They don't look like our work either (well certainly not anything we've done for the last 15 years).

Going off tangent a little, there are 2 classic areas in these engines which will eventually lead to a failure through natural wear & tear/degradation – cylinders gradually migrating oval eventually cracking & crank shaft bearings wearing out. There's a pattern where both seem to start happening at similar mileages (90k-100k upwards). There are obviously lots of cases where engines last longer but there are also others which don't quite make it (we have 2 in at the moment – 1 at 75k and 1 at 80k).

Cylinder cracking isn't too much of a drama – a re-build is needed but the damage is isolated but crank shaft bearing failure is another story and a disaster. The crank & rod will usually be wrecked and potentially the carrier. The debris then usually spreads and will kill the oil pumps and, more often than not gets into the cylinders damaging pistons and potentially the bore surface material. In the very worst cases the rod breaks and the whole engine can be smashed and written off. Cranks, carriers etc are getting much harder to source & second hand values are creeping up.

Consequently, there's a very strong case for replacing the crank bearings as the mileage gets higher before they've failed, particularly if the owners plan is to keep the car for some time.

Hope that helps !

Grant
 
Sorry to add confusion but we're Porsche not offering the short block at a massively discounted price ? I'm sure I read somewhere a figure of around £4K? Given the '100k mile' concern and my useage as a weekend toy of 5k miles for four grand I'd get 20years of useage?!?
 
jond58 said:
Sorry to add confusion but we're Porsche not offering the short block at a massively discounted price ? I'm sure I read somewhere a figure of around £4K? Given the '100k mile' concern and my useage as a weekend toy of 5k miles for four grand I'd get 20years of useage?!?

This was a mis-quote by a magazine, with Porsche UK confirming the prices of short blocks were still way higher (and still with the same inherent faults) than going to Hartech (others are avaialble)
 
jond58 said:
Sorry to add confusion but we're Porsche not offering the short block at a massively discounted price ? I'm sure I read somewhere a figure of around £4K? Given the '100k mile' concern and my useage as a weekend toy of 5k miles for four grand I'd get 20years of useage?!?
i looked into that as well with Design911 Uk but found as my crank is not serviceable I would have lost the return of the surcharge £4K ish?
 
bazhart said:
I'

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as 'closed deck". They are NOT liners nor Nikasil plated. They don't look like our work either (well certainly not anything we've done for the last 15 years).

Hope that helps !

Grant
Thanks for this. I am a bit clearer now on what has failed now. which looks to be the original cylinders.
 
Hartech supplied photos

Photos from Hartech:
 

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photos - open deck

On the open deck photo I can understand now where the weak spots are - I assume it's where the gap between the outer cylinder wall and the block is the greatest.

The pressure in the cylinder is greatest at the top so that's where the strengthening work is concentrated with the trade off between using thicker grade metal for strength and the depth at which go down the sides and restricting the coolant flow around the cylinders. I assume that's what is meant by 'wet' and dry closing? Correct me if I am wrong as I am only just learning stuff.

When did this close decking start to happen on the Porche 996/997 engines and what version are we on now? I was looking at deck closing used by a Sabaru racing team who say they are on version 4 having coupied the Japanese original deck closing design in 2001 and then tweaked it. Version 4 is where they use thicker grade metal at the weak spots and thinner grade at the not so susceptible areas whilst maitaining the cooling channels/properties.
 
Retaining rings

Going back to my engine problems - if the engine has been broken before at some stage would you just do that to put in retaining rings on all 6 cylinders? Do you just take out the engine out to perform preventative maintenance.

How can you tell if the bores are still orginal or have been sleeved at some stage?
[/i]
 
I would open an engine to do preventative maintenance by changing the bearings, I wouldn't do it to fit retaining rings. Most people wouldn't do it at all, believing that these engines will go on well past 100k miles without problems. Some will, some won't.

I would imagine the bores would look different, if liners have been fitted then it won't look like part of the original casting.

MC
 
DAVIDGT996 said:
bazhart said:
I'

The pictures you showed me yesterday David are original Lokasil cylinders but with support rings fitted – hence them being described as 'closed deck". They are NOT liners nor Nikasil plated. They don't look like our work either (well certainly not anything we've done for the last 15 years).

Hope that helps !

Grant
Thanks for this. I am a bit clearer now on what has failed now. which looks to be the original cylinders.

In all honesty, I'd seriously be guided by Hartech on options moving forward. They have probably the most resesrch and dxperience with rebuilding these engines. You can have the engine removed locally and couriered to Hartech or if you have the cover, have the car recovered to Hartech.
 

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