Crankshaft bearing carrier.
 

I have removed & fully stripped my 1997 2.5 Boxster engine after a suspected IMS...caught it just in time...I am now rebuilding with ALL new parts...I found that the engine is an AT Porsche replacement...only had the car a few weeks...my problem is my crankcase bearing carrier...the inserted steel centre section... when I put the halves together DO NOT MATE UP... I have 2 different case halves...I want to replace these with good second hand 1,s...can I use a pair of bearing carries from any Boxster engine.

I`m not following. How is it that the halves don`t mate if they were assembled as a unit originally? Can you elaborate on this? As for your question: the bearing carrier is a separate unit from the crankcase, they are not machined together, hence I believe you can use another one from a different engine. Just make sure to measure all the dimensions before reassembly.

crankshaft bearing carrier.
 

I understand what you are saying...when I stripped the engine it was obvious that someone else : not Porsche : had been inside the engine...rtv etc. so my guess is they have cobbled an engine together : parts from different engines : after a previous engine failure... just to sell the car...I will take a photo so you can tell me if what I have is OK.

I have done a plastigauge check on the 7 main bearings...all 7 were at 002" across the board...so the casings are straight & clearance,s OK...no more panic.

Hello EMWynne, I am not an expert but for this case, using a micrometer will be way more accurate, you may be able to find someone that can help you to meassure with one of those.
Good luck!

It does not hurt to measure the journals with a micrometer for sure. Here `s a thread about the measures:
https://rennlist.com/forums/996-forum/1089034-m96-3-4l-crankshaft-journal-measurements.html#post15250757

Plastigauge is fine to give you an idea whether the clearances are ok and even at each bearing. Check the thrust bearing and the endfloat too. Also, when you do plastigauging make sure you tighten the 12 bolts in the correct sequence and to the correct torque.

Crankshaft bearing carrier.
 

Guys, I,m an ex FIA. GT3 mechanic...& have been around engines for 60 years...just not this type of Porsche engine...classic 911 no problems...I,ve done the micrometer & bore gauge checks but the 1 thing that does not tell me...because of the missmatched insert... is my casing straight...so after checking my crank with a clock gauge in Vee blocks to determine this...I then did the plastigauge to assure myself the casing halves were straight...remembering that the engine ran like **************** when I bought the car....now I,m happy to continue with the build...I have some pictures, but not on a file so they will not post on the site.

Looks like you are on the right track then. I rebuilt mine from scratch too, look around at my build thread, you may find useful things here about the bearing carrier: http://986forum.com/forums/show-tell-gallery/73917-blue-boxster-resurrection-project-5.html

Crankshaft bearing carrier.
 

Love your post 104 & the use of the center,s of a toilet roll to protect the con rod...thanks for the help...onwards & upwards.

Crankshaft bearing carrier.
 

Homoboxter, When I chacked my bearing clearance with the plastigauge I only torqued the bolts to 20 lb/ft...25 nm...now on final installation torquing to 20 lb/ft then 90 degree my crankshaft locks up solid...checked every thing again & I have NO endfloat...the carrier with washers & the thrust faces on the crank are exacly the same width...as there is only 1 washer size is it the done thing with this engine to set the float by rubbing the washers on emery paper to the correct float at 002 "/007".