Bore Scoring - Preventative measures?

mzmini · 23 Jul 2016

I would like to add to some of the points that Phil 997 has stated.

When I was looking for a 997, I spoke to Baz at Hartech about the pros and cons of the 997 engine. Baz was brilliant and chatted for 20+ minutes and the bottom line was as follows: 3.6 manual least likely to suffer bore score; 3.6 tip a little more; 3.8 C2S manual a little more still; and finally 3.8 C2S tip that was driven around town - the most. Armed with all the info from top Porsche engine rebuilders in the country, I did just as I always do - my own thing and brought a 3.8C2S manual. Never had a PPI or bore score check. I let my eyes be my guide and my pocket be my pride, and bought a car without those 2 checks that "looked and felt right". 4 years on still going strong. I guess Phil and I have been the lucky ones

I've also, very recently bought a 987 Boxster 3.4S for my wife. Again no PPI or bore score check - just went on the history of the car that was spot on and had previously been sold by a very reputable dealer.

My daughter's 986 Boxster did have a PPI but no bore score check and no signs of any issues thus far

There will be a percentage of cars that go wrong - if it's 10% that still means 90% won't! I also own a Land Rover Discovery and if I took heed of all the horror stories on those, I'd be driving something Japanese ...... :grin:

High value cars will generally be ore expensive to put right that than your average Ford Mondeo - but that's the choice we make. Good luck :thumb:

Phil 997 · 23 Jul 2016

mzmini said:
I would like to add to some of the points that Phil 997 has stated.

When I was looking for a 997, I spoke to Baz at Hartech about the pros and cons of the 997 engine. Baz was brilliant and chatted for 20+ minutes and the bottom line was as follows: 3.6 manual least likely to suffer bore score; 3.6 tip a little more; 3.8 C2S manual a little more still; and finally 3.8 C2S tip that was driven around town - the most. Armed with all the info from top Porsche engine rebuilders in the country, I did just as I always do - my own thing and brought a 3.8C2S manual. Never had a PPI or bore score check. I let my eyes be my guide and my pocket be my pride, and bought a car without those 2 checks that "looked and felt right". 4 years on still going strong. I guess Phil and I have been the lucky ones

I've also, very recently bought a 987 Boxster 3.4S for my wife. Again no PPI or bore score check - just went on the history of the car that was spot on and had previously been sold by a very reputable dealer.

There will be a percentage of cars that go wrong - if it's 10% that still means 90% won't! I also own a Land Rover Discovery and if I took heed of all the horror stories on those, I'd be driving something Japanese ...... :grin:

High value cars will generally be ore expensive to put right that than your average Ford Mondeo - but that's the choice we make. Good luck :thumb:

Thank you Chris, That is exactly the same information that I have been given by highly qualified Porsche specialists, and a very very good point made about if 10% fail that means 90% don't ,which is probably better odds than having an accident, and personally I would rather drive a 911 with those odds than get better odds but have to drive a boring transportation box to get them. live fast and all that :grin: :grin: :thumb:

volks_womble · 23 Jul 2016

mzmini said:
I also own a Land Rover Discovery and if I took heed of all the horror stories on those, I'd be driving something Japanese ...... :grin:

That made me smile... I have owned many vehicles bearing the green oval - discoveries, defenders and range rovers new and old... Why do you think I am wary of horror stories??? :dont know:

Thanks for your experiences

Phil 997 · 23 Jul 2016

volks_womble said:
mzmini said:

I also own a Land Rover Discovery and if I took heed of all the horror stories on those, I'd be driving something Japanese ...... :grin:

Click to expand...

That made me smile... I have owned many vehicles bearing the green oval - discoveries, defenders and range rovers new and old... Why do you think I am wary of horror stories??? :dont know:

Thanks for your experiences

I was thinking of buying a land rover, when my wife asked why , I said because I sleep too well at night :floor: :thumb:

mzmini · 23 Jul 2016

Hi Volks_ womble I can promise you the green oval is a far far more bumpy ride than a 911 IMHO if your man enough for a Land Rover you must have balls of steel ,a Porsche is plain sailing after a FF Range Rover, the must heart breaking car on 4 wheels or perhaps I should say on a ramp
:floor: :floor:
happy hunting
MZ

infrasilver · 23 Jul 2016

This subject will always divide opinion and there have been many many debates on here when there will never be a point, where people see eye to eye.

There are some facts out there and I mostly take on board what Hartech say as they have seen more M96 engines than anyone and that includes OPC's and after 3 engine rebuilds myself I have never had to do one due to bore scoring or IMSB so even if you had a so called bullet proof engine rebuild, other (normal engine issues) things can fail.

I drive the nuts off mine still without the worry of it failing and probably enjoy my 996 more than most do.

bazhart · 29 Jul 2016

Although I am somewhat reluctant to enter into this spirited debate - there are perhaps a few points that may be of interest.

Firstly rebuilds can be successfully carried out for far less than the figures quoted above but most owners that choose Hartech do so because we offer the best solutions and those owners and businesses that choose us usually also want all other weaknesses addressed at the same time and often various other issues fixed (like old radiators, coolant pumps, new clutch etc etc) whereas some of those seeking a cheaper alternative (with a less comprehensive rebuild) tend to go elsewhere (although actually our prices for "like to like" rebuilds are very similar and the quality is second to none - as is the after care support). We often get them back from rebuilds elsewhere as well to do the job properly.

Typical of this would be the choice between replacing one scored cylinder - just the three on bank 2 or all 6. Most of our customers have all 6 done at the same time (for which we offer a significant cost reduction due to commonality during machining setting times etc).

Secondly, the 3.6 has similar cylinder wall thickness to the 3.8 - the problem here is that the capacity (and torque) increases roughly with the square of the cylinder diameter whereas the cylinder tube circumference increases directly - so as the engines get bigger bores - the cylinder walls of an open deck design should really get thicker to compensate - but don't (possibly because the space for coolant would then be more severely reduced).

We see far more 3.8's than anything else but there may be a more subtle reason than simply technical. Given the choice between a 3.6 and 3.8 those who want to thrash the performance out of a car will inevitably choose the 3.8 whereas those for whom outright performance is not their main concern may decide on the 3.6 and therein reduce loads and temperatures accordingly. This would be particularly relevant for jerk (acceleration change) and hence torque loading and thermal shock.

The rate at which piston coatings wear, cylinders distort, crankshaft bearings wear and chains strain is partly proportional to loads and usage (and therefore full throttle loads and capacities) - partly due to mileage and age (with some influence from oil choices) and also I think is influenced by random quality variations in the Lokasil that forms the cylinder bore.

If these engines had been fitted with closed deck Nikasil alloy cylinders (like the GT3 and Turbo's and our engines) the reliability (especially after the bigger IMS bearing was fitted) would be on a par with most other similar modern sports car engines.

I think it would be reasonable to note that Porsche sports cars probably cover a higher average mileage than most other similar sports cars (as they are bought to use more than just park up and running costs are generally reasonable) and many other sports cars at similar mileages need attention to engines etc. The main exceptions will be cars with more cylinders of a smaller diameter but they tend to be heavier and less nimble and often don't drive like a Porsche!

To some extent the coolant flow changes also contributed to the problems once the plastic coated pistons were used because so little coolant is directed into the cylinders (and the control of that flow handicapped in later engines by introducing a single universal head gasket instead of a RHS and LHS one). Although we modify this a little we are limited by the basic design that reverted to a more traditional flow scheme in the Gen 2 engines.

Porsche did a fantastic job of performance against cost with these cars and the vast majority are acceptably reliable (although this may also be a reflection of the small number of owners who actually exploit the potential performance fully).

The engines will last longer if they are never thrashed by any owner - but then - who wants to drive them like that?

Baz

p.s. just my opinions and I don't have time to enter into further debate on them - sorry - too much else positive to deal with!

Phil 997 · 29 Jul 2016

bazhart said:
Although I am somewhat reluctant to enter into this spirited debate - there are perhaps a few points that may be of interest.

Firstly rebuilds can be successfully carried out for far less than the figures quoted above but most owners that choose Hartech do so because we offer the best solutions and those owners and businesses that choose us usually also want all other weaknesses addressed at the same time and often various other issues fixed (like old radiators, coolant pumps, new clutch etc etc) whereas some of those seeking a cheaper alternative (with a less comprehensive rebuild) tend to go elsewhere (although actually our prices for "like to like" rebuilds are very similar and the quality is second to none - as is the after care support). We often get them back from rebuilds elsewhere as well to do the job properly.

Typical of this would be the choice between replacing one scored cylinder - just the three on bank 2 or all 6. Most of our customers have all 6 done at the same time (for which we offer a significant cost reduction due to commonality during machining setting times etc).

Secondly, the 3.6 has similar cylinder wall thickness to the 3.8 - the problem here is that the capacity (and torque) increases roughly with the square of the cylinder diameter whereas the cylinder tube circumference increases directly - so as the engines get bigger bores - the cylinder walls of an open deck design should really get thicker to compensate - but don't (possibly because the space for coolant would then be more severely reduced).

We see far more 3.8's than anything else but there may be a more subtle reason than simply technical. Given the choice between a 3.6 and 3.8 those who want to thrash the performance out of a car will inevitably choose the 3.8 whereas those for whom outright performance is not their main concern may decide on the 3.6 and therein reduce loads and temperatures accordingly. This would be particularly relevant for jerk (acceleration change) and hence torque loading and thermal shock.

The rate at which piston coatings wear, cylinders distort, crankshaft bearings wear and chains strain is partly proportional to loads and usage (and therefore full throttle loads and capacities) - partly due to mileage and age (with some influence from oil choices) and also I think is influenced by random quality variations in the Lokasil that forms the cylinder bore.

If these engines had been fitted with closed deck Nikasil alloy cylinders (like the GT3 and Turbo's and our engines) the reliability (especially after the bigger IMS bearing was fitted) would be on a par with most other similar modern sports car engines.

I think it would be reasonable to note that Porsche sports cars probably cover a higher average mileage than most other similar sports cars (as they are bought to use more than just park up and running costs are generally reasonable) and many other sports cars at similar mileages need attention to engines etc. The main exceptions will be cars with more cylinders of a smaller diameter but they tend to be heavier and less nimble and often don't drive like a Porsche!

To some extent the coolant flow changes also contributed to the problems once the plastic coated pistons were used because so little coolant is directed into the cylinders (and the control of that flow handicapped in later engines by introducing a single universal head gasket instead of a RHS and LHS one). Although we modify this a little we are limited by the basic design that reverted to a more traditional flow scheme in the Gen 2 engines.

Porsche did a fantastic job of performance against cost with these cars and the vast majority are acceptably reliable (although this may also be a reflection of the small number of owners who actually exploit the potential performance fully).

The engines will last longer if they are never thrashed by any owner - but then - who wants to drive them like that?

Baz

p.s. just my opinions and I don't have time to enter into further debate on them - sorry - too much else positive to deal with!

Baz ,Another great and informative post :worship: with some excellent logical reasoning why some do and some don't seem to suffer the issue. thank you :thumb:

bazhart · 29 Jul 2016

And today we have just stripped an engine from Denmark with bore scoring to find the big ends have worn through the white metal and in two cylinders most of the copper (that some versions have) has disappeared and the engine would have suffered a very expensive crankshaft failure as well in the very near future - all showing that the engines will benefit from a full rebuild at some stage in their lives and better to do the job properly then and before other failures add to the cost (pictorial evidence due to be posted on our web site shortly)

Baz

pothole · 9 Aug 2016

Hi Baz

Quick question re your post above. You mention driving hard and a correlation with these issues.

This makes me wonder. My car (3.4 987)had a replacement engine at 42k miles for bore scoring. Having spoken to the previous owners, I am fairly confident that it wasn't driven hard during that period.

Meanwhile, I've done 40k on the new engine and frankly thrashed the pants off it at literally every opportunity, averaging 17mpg over that period.

The new block doesn't seem to use much oil at this stage where the old one had a horrendous drinking habit at the same mileage. I'm aware there are variables, but I would have thought if thrashing the engine was related to bore scoring, my new block would be in a very bad state by now.

I always warm the car up carefully, but I am struggling with the notion that thrashing these engines is strongly correlated with bore scoring...

bazhart · 9 Aug 2016

OK perhaps I have mislead you by my terminology. In our new interactive buyers interactive (almost finished) i have taken the time to explain in more detail.

The problem is always high torque at lower revs - this is when bore scoring occurs and it is most often the result of pulling away with high throttle openings after a period of rest when the engine is very hot (for all the reasons I have covered over the years).

This is why tiptronics seem more prone because they naturally set off in second and the torque converter raises the revs slightly to a very high torque area of the torque graph and this in turn means that the piston is pushing hardest against the cylinder wall when the oil is very hot and thin and if a loose piece of silicon is present it may penetrate the oil film or be bigger than the space available and damage the plastic piston coating leading to a scoring failure.

I have also made it clear that we are sure that the quality of the Lokasil bore material varies - so some release more silicon more often than others.

So we always recommend not to open the throttle too high immediately after a period of rest (say at lights) following a spirited run - just long enough to allow the coolant to circulate, the heat soak to diminish and the oil to get cooler and thicker.

However I have also made it clear that for racing Lokasil is often OK because all the work is at higher revs.

When the engine is revving higher the piston seems to follow a straighter path up the cylinder wall and centralise itself more (if you want confirmation read more about piston scuffing on the Internet).

Now my expression "thrash" refers to someone who is a full throttle man whenever there is room to accelerate. If this is in a manual we find people change gear at higher revs than they do in a tiptronic (where the torque is lower) - so we have always said it is better to rev the engine when under load and avoid high torque applications at low revs and especially if the engine is particularly hot at the time.

So someone who never drives fast is less likely to experience bore scoring. Someone that likes booting it from low revs (but not revving the engine out) is more likely to experience bore scoring and someone that only ever revs the engine before applying full throttle may have a better outcome (although then they will probably wear out the big ends more quickly).

But there is no hard and fast rule because the quality of the cylinder wall material we find varies between engines and this results in different amounts of ovality in the same cylinder block and in different cylinders (not always in the same place) so it is entirely possible for the same driver to experience a reliable engine or an unreliable one despite driving both the same.

You say you always warm up your car before applying high loads and that is excellent and will help but however you drive your particular engine will last longer if you follow my advice - but that will only be longer than it was going to last anyway if that advice was ignored and will not cross refer between different cars because the interior surfaces of the Lokasil bores will vary too much for consistent and reliable statistics to result.

For more information I would await the availability if our new interactive engine guide - it is not far away now and contains more readable information than our very old guide presently available and in a more reader friendly way.

Baz

Bore Scoring - Preventative measures?

mzmini

Barcelona

Phil 997

Le Mans

volks_womble

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Phil 997

Le Mans

mzmini

Barcelona

infrasilver

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bazhart

Barcelona

Phil 997

Le Mans

bazhart

Barcelona

pothole

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bazhart

Barcelona

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