Thanks to both of you (Mike, Marc) for the links. *NM*

Folks,

Since i'm looking at a range of motor options for my "new" project car, i wanted any data you might have on the pre-DFI 3.4.

1. overall reliability etc
2. IMS durability - let's stay away from religion and just discuss engineering differences between 987 and 986 motors
3. I understand it is not easy to put an LN replacement in a M97? I guess i should just call Charles....
4. Any harness 'gotchas" if mated to a 2000 S chassis/tranny?

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Grant:
If you haven't already done so, check the planet 9 site and specifically the competition and modification forums; lots of pertinent info. The Cayman register is another good site.

From the comments on those forums it would seem that he IMS is less of an issue on the 987 3.4L compared to earlier cars, but track use raises the issue of proper oiling the of main bearings in turns and there have been a number of failures (some multiple failures in the same car) of the main bearing/connecting rods-bolt while tracking the car. There is a lot of ideas floating around on what might help--, accusump, better baffling, different oil...-- but nothing definitive.

The general agreement is that it only occurs in cars with slicks, generating high-Gs, and, implicitly, well/quickly driven.

I'm mostly interested in "hard but normal use" conditions, and about replacement of the IMS (need, feasibility) in particular.

Over time i can always add a baffled oil pan and/or accusump. Not a huge savings doing it out of the car....

i also participated in a discussion on Rennlist with Jake and others where a culprit was hgih oil temps. Much back and forth until i suggested thick oil good to 275 deg+. Even Jake said "yea, well, that would work". Talk about making a mountain of a mole-hill, more of the 'Porsche says 0W40' , 'n-spec ashtrays' mumbo-jumbo, and suddenly people are spending $3k on fixes that dont work!

How's the toy?.... I may buzz you offline sometime.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
The general agreement is that it only occurs in cars with slicks, generating high-Gs, and, implicitly, well/quickly driven.

I'm mostly interested in "hard but normal use" conditions, and about replacement of the IMS (need, feasibility) in particular.

Over time i can always add a baffled oil pan and/or accusump. Not a huge savings doing it out of the car....

i also participated in a discussion on Rennlist with Jake and others where a culprit was hgih oil temps. Much back and forth until i suggested thick oil good to 275 deg+. Even Jake said "yea, well, that would work". Talk about making a mountain of a mole-hill, more of the 'Porsche says 0W40' , 'n-spec ashtrays' mumbo-jumbo, and suddenly people are spending $3k on fixes that dont work!

How's the toy?.... I may buzz you offline sometime.

Grant

There have been a few guys reporting bearing failures on street tires as well.

Regarding the IMS replacement, all the mechanics I talked to said figure a minimum of $5K to do just the IMS if you have to pull the motor and split the case; then the other stuff comes up as "while you're in there" --how about lifters, chain tensioners, water pump and the list goes on...

I think I saw the thread on the high temps possibly being the major culprit and it seemed make sense. Somebody on the 986 forum had lots of data on this which I'll try to find.

The new toy is a hoot; I'm trying to get as many miles on it as possible but the weather is not cooperating.

Quote
grant
Folks,

Since i'm looking at a range of motor options for my "new" project car, i wanted any data you might have on the pre-DFI 3.4.

1. overall reliability etc
2. IMS durability - let's stay away from religion and just discuss engineering differences between 987 and 986 motors
3. I understand it is not easy to put an LN replacement in a M97? I guess i should just call Charles....
4. Any harness 'gotchas" if mated to a 2000 S chassis/tranny?

Grant

for 2 years. There haven't been too many "My 987 engine blowed up" posts but that's not scientific to be sure.

Unless someone has hard facts and is willing to share them (one of the larger indy engine rebuilders/tuners and I think you know who I mean....) all I can offer is guesses. One being the reliability is no worse than the older engine and probably better. Or is that two guesses?

Some, at least one I know of, have read of, indy engine builders/tuners in the UK believe the 987 engine is actually worse in some areas than the engine that proceded it.

(More unscientific commentary: I was not afraid of the 3.4l engine buying an 08 Cayman S in 09. Unfortunately my time with the car was shortlived so we'll never know how this would have turned out. Also, I had absolutely no plans on tracking the car, though I certainly intended to enjoy it as spiritedly as possible on public roads.)

If you are that concerned about the IMSB go with the previous generation engine which has the easier to replace IMSB and replace the IMSB with LN retrofit. If you track the car alot this IMSB might be an annual service item.

As MikeOH touched upon the IMSB ain't the only fly in the oinment. These engines are just not suited to tracking having problems in the oiling department. There are band-aids, some rather nicely engineered, but they are band-aids nonetheless.

Thus you have to consider it a real possibility if you track the car that the engine will suffer and maybe catastrophically. This is -- though no one likes to hear it -- is the cost of doing business so to speak, the cost of tracking. Some pay the fee, some don't.

Regarding mixing/matching engines, for wiring harness issues, and other issues, all I can suggest is you visit this site:

[www.pelicanparts.com]

and see what you can gleam from the various articles.

1. With the LN and proper lubrication, the IMS i think will be a permanent fix. Track use is in many cases the recipe for LONGER life. I mean, let's be real - Pedro ran his on the track (slicks, instructor) for years and years. I ran my LN equipped 2.7 (albeit a bit slower) for years and have UOAs that indicate near zero wear. It will continue to run - and i wager trouble-free. So i'm very comfortable that with the silly sealed bearing gone, things will be OK (and a near weak link will emerge, of course)

2. I'm not (yet) fast enough to starve cyl #6. I supposed that's my warped goal :-)

3. Agree - too new to have meaningful data on 987s. That's why I'm specifically asking ONLY for info on the construction of the bearing. I'll make my own determination from that. I have heard its 2x the size of the original and uses sump lubrication. Concur? Differ?

Oh, i do plan to ask Charles too. Mostly about how hard it is to replace. I think, very. Which may lead me to your conclusion - get a 3.2 and make it as solid as possible.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Grant:
Here's link to a guy I see a the track a lot, that has been helping Jake with his developmental work for a few years.
He has a 2000S that now has 3.6L in it . He has a chart with oil temps at different ambient temps.
[www.m96infosource.com]

Grant

gee-lenahan-at-gee-mail-dot-com

Another thread, this one from Planet -9, on oil pressure drops and quite a bit of data acquired with discussion on it.
[www.planet-9.com]

If high oil temps were determined to be one of the main culprits of the bearing failures, wouldn't the obvious fixes include:

-higher viscosity oil (5W-50)
-external oil coolers
-improvements to the cooling (water) system
-Oil pressure/temp gauges

as this would require a substantial redesign of the engine and that was saved for the DFI/IMSB-less engines.

It is probably bigger with perhaps other changes to address whatever shortcomings the previous bearings had that were at the root cause of the failure.

Quote
grant
With the LN and proper lubrication, the IMS i think will be a permanent fix.

... consider the replacement with LNE or any other IMS bearing a permanent fix.
Every time the tranny comes down for a clutch, replace the bearing.
YMMV
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

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