Possible rebuild

[bazhart]

You are very unlikely to experience bore scoring, cracking or D chunking with a 3.2 engine but always a good idea to try everything to check a used engine before purchase.

Baz

 

[bazhart]

I checked the prices yesterday. I think some previous posts have been a little misleading as a result.

The short motor price for a Boxster S is around £5000 (£6000 with Vat), 996 3.4 £5382 (£6028 with Vat), 996 3.6 £5692 (£6830 with Vat), 3.6 997 £11296 (£13555 with Vat), 3.8 997 £12,409 (£14890 with Vat) and a 3.4 Cayman S £10707 (£12848 with Vat). Remember these will be to the same spec as the original (except possibly the IMS bearing).

Reflecting on the context & direction this thread has taken, if we were to just receive a short motor and the customer asked us to replace just the crank bearings it would cost around £1600 + VAT (for a 3.2 or 996 3.4).

We would of course recommend lots of other things which would be specific recommendations for the model and engine in question.

A typical example would be for an early 996 3.4 with duplex crank to IMS chain drive & the earlier pistons (traditionally not prone to bore scoring and usually re-useable) – we could re-build it with new crank bearings, chains, guide rails & piston rings, strengthen the cylinders & carry out a conversion to the intermediate shaft and fit a much larger bearing (similar to the 2006 onwards cars) for around £3500 + Vat (£4200 with Vat) and you keep the original engine number.

For different models we would make different recommendations which add to the cost, so for those prone to bore scoring we would suggest our superior aerospace alloy Nikasil plated cylinders etc.

Over-sized engines are also available but more expensive (due to economies of scale, lower cylinder support rings and new bespoke pistons).

The above prices are all geared towards just a short motor (adapting to the direction this thread has followed). Readers need to realise that a short motor is just half an engine so removal of the engine is still needed along with its partial strip down, cleaning & preparation for re-assembly, transfer of all the top end engine components like cams, heads etc, new associated gaskets & seals (like head gaskets etc), strip & clean ancillaries, re-fit to engine, re-fit unit to car, re-commission with new fluids, a/c re-charge etc. & test. This obviously comes at a cost to those unable to do it all themselves.

We also suggest cylinder head overhauls etc.

We can of course offer all of the above but home mechanics/other garages may wish to carry out some/all of this work themselves.

We have lots of garages (including well know Porsche Specialists and main dealers) who send us just blocks, short motors, long motors & complete cars.

We can fit an Intermediate Shaft with the new larger bearing (for both older roller chain and newer Hivo chain engines) and we're in the process of preparing exchange block/piston packages for capacity conversions, mainly for overseas customers.

There is little point in buying in just the new 'heavy metal" parts for a rebuild since I added up the prices of a 3.4 Crankshaft, Carrier and Crankcases and it came to £9534 (£11440 with Vat). It is this kind of price structure that will make early rebuilds increasingly attractive before further wear and damage make the addition of new components too expensive.

All work on engines is tailored to the customer and the results of the in depth inspection and measurement of his parts from which alternative recommendations follow and although the outcome is all recorded so a computer system works out the final prices and any discounts – we are not about to present all that work file in total for others to copy (it took ages to create).

My colleague, Grant, has dealt with so many now for so many years that he has a very logical way of explaining his views on preventative re-builds (and I can't fault it) but he's a little reluctant to post it on here as he expects to then need to spend precious time having to defend his views (but overall it can save people a lot of money in the long run). I'll see if I can talk him into it !!

However - we have now become so busy if you are considering a rebuild (or need one) I would recommend that you speak to him and then compare the outcome with an accurate estimate of the cost by other methods – which you will almost certainly find cost you more for a less high quality solution.



We made a hardened drill jig for our exhaust studs about 15 tears ago (and it is still going strong) and we have found that the original studs have hardened just through heat and cool cycles - so maybe not because you tried to weld to them.



Baz

 

[love154]

Ive never heard of chains snapping on any 911, changing them would be a waste if doing that only!! I change my oil in my car 3 times a year after rebuilt due to bore scoring and always warm my engine up to temp before i drive..

J

do you leave on tickover to warm up

 

[Alex]

:grin:

 

[bazhart]

Well 997 you have heard of chains snapping now because we have over the years had to rebuild engines specifically because the chain has snapped and in one case the broken chain rolled down into the lower casing, piled up on itself and broke out a piece of the main block casting - result scrap. Of course the more engines you rebuild the more with unusual failures like this you get to see.


Unless the reason that the engine came in for rebuild was a broken chain - apart from that - all rebuilds have options which are explained to customers and we follow their choices - so even if your engine ever came here (which seems unlikely) you could choose not to have the chains replaced and then if the engine ever failed because of a chain break you would obviously not be covered by our warranty.

Chains stretch so the distance between the roller and the next one slightly increases. At the same time the sprockets wear down so the distance between one tooth root (where the roller sits) and the next - one reduces chordally and as a result the loads are gradually shifted from being shared among several rollers, plates and teeth to just one roller and pair of plates and can result in a failure.


This was the basic cause of the 944 S2 cam chain failures that we first warned about over 20 years ago when Porsche claimed the chains were a "service for life" item. Initially competitors reported we were wrong, then the explanation gained credibility as more failed and eventually it became an accepted preventative change. Porsche later modified the tooth profile to help the sprockets last lomger as the chains stretched.


It will be a great day when contributors stop trying to fault the combined experience of a lot of well respected engineers and their advice by throwing in posts with no hands on backing.

Baz

 

[jond58]

So oil analysis back!!!!

Bit of brief history. The car is a 2000 3.4 (Big25's old car). Regularly serviced, yearly throughout its life, IMS seal flipped early on by William Crawfords and currently on a bit under 90k miles. I have and oil and filter twice a year and have a magnetic sump plug. I've never seen anything to concern me or felt/heard anything untoward I simply believe with high repair costs and low tolerances on engines designed to make a decent amount of power the paranoia is inevitable!!

ANYWAY

CR 0
PB 0
NI 0
FE 3
AL 2
CU 2
NA 3

This oil had done 2500 miles. Id say thats a fair clean bill of health. Id recommend an oil analysis and obviously I'll continue with these now, it will set your mind at ease and you can see IF (WHEN lets be honest here) that rebuild may be imminent.

 

[sackerley]

jond58 - Having the oil sampled isn't something I've done yet, maybe I need to?! So I've no idea what those figures mean.

What figures would suggest a rebuild?

 

[jond58]

I think, and some one will confirm, high lead (pb) and high copper (cu) tend to be from bearings. That was my main area to watch anyway, a 3.4 is probably, maybe, perhaps most likely to fail at the crankshaft with wear or crank bearings been the issue!