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Fabs911
Newbie


Joined: 18 Jan 2020
Posts: 12



PostPosted: Mon Jan 20, 2020 8:46 pm    Post subject: Reply with quote

adamw wrote:
Fabs911 wrote:
I have already booked to replace the IMS bearing and I'll still keep the eye on it


What bearing you going for ? Original or aftermarket ?

Pop Corn


Aftermarket. It is at least what all independent specialists recommended me

What you guys think?
 
  
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adamw
Estoril


Joined: 09 Jul 2009
Posts: 3976
Location: West Sussex

1998 Porsche 996 Carrera 2

PostPosted: Mon Jan 20, 2020 9:13 pm    Post subject: Reply with quote

Fabs911 wrote:
adamw wrote:
Fabs911 wrote:
I have already booked to replace the IMS bearing and I'll still keep the eye on it


What bearing you going for ? Original or aftermarket ?

Pop Corn


Aftermarket. It is at least what all independent specialists recommended me

What you guys think?


Think if I were replacing id also consider aftermarket.
Wouldn’t consider the LN solution from what I’ve heard of late.

I’ve heard about a cylindrical type bearing from eps that looks interesting.
What have you been recommended?
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98’ 996 C2 aero, Swartz Black, GT3 style fixed buckets, GT3 momo steering wheel, GT3 wheels, KW’s + lots more

EX : 02' 996 Turbo Coupe ( May 17 - Sept 19 )
EX : 95' 993 C4 Coupe ( Dec 10 - Oct 16 )
EX : 00' 996 C2 Cab ( Jul 09 - Oct 10 )
EX : 03' 986 Boxster S ( May 06 - Dec 08 )
 
  
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DarthFaker
Trainee


Joined: 13 Jun 2019
Posts: 93
Location: 1999 Carrera 4 Aerokit


PostPosted: Mon Jan 20, 2020 9:23 pm    Post subject: Reply with quote

I can't comment on what solution is best but I chose the roller bearing type.

So far it's survived 1100 miles Floor

I'll let you know in a few years if it was good or not.
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8560
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Mon Jan 20, 2020 9:26 pm    Post subject: Reply with quote

jond58 wrote:
To be honest depending on the car I’d be less worried about the ims exploding than I would be about the crank bearing destroying itself!!!


I tend to agree, if an IMSB goes your engine will require a full rebuild and need quite a few differing parts, if your crank bearings go you will still need to do a full rebuild but it's getting hold of a used crankshaft that could actually stop the rebuild going ahead at all and a new crankshaft is over £3k just for that single part, it is worth looking after that crankshaft and is worth doing a preemptive rebuild just to keep the CS in good order.
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jond58
Spa-Francorchamps


Joined: 19 Jun 2017
Posts: 279
Location: York


PostPosted: Mon Jan 20, 2020 10:17 pm    Post subject: Reply with quote

As I’d said depends upon the car. Mine is an early 3.4, dual row ims and seemingly far less likely for bore score etc etc. That said I do believe that any ‘high power naturally aspirated’ engine will lunch something internally at some point. The weakness tends to be the crank from statistics and as stated they are seem like they are made of unobtainium these days!
I think there is a market for preemptive rebuilds. If, at a reasonable cost, you refresh the engine and save things like the crank it’s got to be worth it. I come from motorbikes where rebuilds are a yearly occurrence!!
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Fabs911
Newbie


Joined: 18 Jan 2020
Posts: 12



PostPosted: Tue Jan 21, 2020 1:48 pm    Post subject: Reply with quote

adamw wrote:
Fabs911 wrote:
adamw wrote:
Fabs911 wrote:
I have already booked to replace the IMS bearing and I'll still keep the eye on it


What bearing you going for ? Original or aftermarket ?

Pop Corn


Aftermarket. It is at least what all independent specialists recommended me

What you guys think?


Think if I were replacing id also consider aftermarket.
Wouldn’t consider the LN solution from what I’ve heard of late.

I’ve heard about a cylindrical type bearing from eps that looks interesting.
What have you been recommended?



I didn't really ask but I'll asked them
 
  
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Fabs911
Newbie


Joined: 18 Jan 2020
Posts: 12



PostPosted: Tue Jan 21, 2020 1:50 pm    Post subject: Reply with quote

infrasilver wrote:
jond58 wrote:
To be honest depending on the car I’d be less worried about the ims exploding than I would be about the crank bearing destroying itself!!!


I tend to agree, if an IMSB goes your engine will require a full rebuild and need quite a few differing parts, if your crank bearings go you will still need to do a full rebuild but it's getting hold of a used crankshaft that could actually stop the rebuild going ahead at all and a new crankshaft is over £3k just for that single part, it is worth looking after that crankshaft and is worth doing a preemptive rebuild just to keep the CS in good order.


I agree with you, with crankshaft the IMSB should be the least of my problems.
 
  
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Fabs911
Newbie


Joined: 18 Jan 2020
Posts: 12



PostPosted: Tue Jan 21, 2020 1:53 pm    Post subject: Reply with quote

jond58 wrote:
As I’d said depends upon the car. Mine is an early 3.4, dual row ims and seemingly far less likely for bore score etc etc. That said I do believe that any ‘high power naturally aspirated’ engine will lunch something internally at some point. The weakness tends to be the crank from statistics and as stated they are seem like they are made of unobtainium these days!
I think there is a market for preemptive rebuilds. If, at a reasonable cost, you refresh the engine and save things like the crank it’s got to be worth it. I come from motorbikes where rebuilds are a yearly occurrence!!



What years are more prone for bore scoring?
I thought the early 3.4 and the late 3.6 were more prone for that
 
  
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8560
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Tue Jan 21, 2020 2:10 pm    Post subject: Reply with quote

3.8 worst then 3.6
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jond58
Spa-Francorchamps


Joined: 19 Jun 2017
Posts: 279
Location: York


PostPosted: Tue Jan 21, 2020 9:14 pm    Post subject: Reply with quote

I think the early ones did the d chunking although those that were seem to have if you get my drift. The 3.6 been a bigger bore seems more prone to scoring. I’ve done the low temp stat thing, bigger sump etc. There’s only so much you can do to prevent problems and only so much worrying you can do!?! If it goes kablamo it happens!!
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wasz
Paul Ricard


Joined: 28 Dec 2012
Posts: 3072


1999 Porsche 996 Carrera 2

PostPosted: Fri Jan 24, 2020 3:44 pm    Post subject: Reply with quote

WBAC.com or flatbed to an engine rebuilder.

Sounds like the crank bearings.
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Fabs911
Newbie


Joined: 18 Jan 2020
Posts: 12



PostPosted: Sat Jan 25, 2020 10:49 am    Post subject: Reply with quote

jond58 wrote:
I think the early ones did the d chunking although those that were seem to have if you get my drift. The 3.6 been a bigger bore seems more prone to scoring. I’ve done the low temp stat thing, bigger sump etc. There’s only so much you can do to prevent problems and only so much worrying you can do!?! If it goes kablamo it happens!!


I have been searching about that as well and indeed can happen to any 996 of 997.1.
it's another thing to keep in mind e look for and prevent it.
However, it doesn't seem that I have any symptoms of bore scoring but I'll keep my on it. and try the install a Low-Temperature Thermostat and not worry to much.
 
  
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bazhart
Approved Trader


Joined: 20 May 2009
Posts: 1021
Location: Bolton Lancashire


PostPosted: Sat Jan 25, 2020 11:05 am    Post subject: Reply with quote

There was a down and up side to the earlier engines (up to the last 996 3.4's) which cracked or "D" chunked (because the thin open deck cylinders were not strong enough to avoid flexing and stretching oval until they cracked). However they also used hard iron coated pistons so did not suffer bore scoring.

Later engines (late 3.4 996's, 3.6, 3.8 and Cayman S engines) changed the alloy casting mix to include bigger silicon particles making the cylinders stronger (unlikely to crack) - so far so good - but then combined that with softer coated pistons that then can score bores.

All Lokasil and Alusil bores (like all wear modes in any parts) gradually release particles. The size of the particles influences the damage they can do.

Most metallic particles are too small to not simply sit between the metal parts inside the oil film and flow round to be picked up by the oil filter. The silicon particles in Alusil and Lokasil are big enough to potentially cause problems which the harder iron coated pistons minimised. The larger particles in the later engines combined with softer piston coatings resulted in damage over time with some cylinders (and some coatings on some pistons) turning out better than others and introducing a random element to predicting life span.

Nikasil also has silicon particles but they are about on tenth of the size of those in Lokasil or Alusil and better bonded into the substrate with very slow release rates anyway and can survive without any piston coatings as a result.

Support rings in the top of the earlier engines could have removed or eliminated cracking and "D" chunking while fitting the hard iron pistons to the later stiffer cylinders could have avoided scoring.

Out of the frying pan into the fire seems appropriate to describe the outcome.

Baz
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