Blue boxster resurrection project

[Homeoboxter]

Originally Posted by Smallblock454

Hi Greg,

first step is always to measure all parts, especially the cylinder heads. Because this is an full alloy engine you have to check for flatness, warps and if anything is straight.

You can check the head surface by using a steel ruler. Put the ruler on the head and put a torch behind the ruler so it shines in your direction. If you can see light come through between the head surface and the ruler, in general the head needs to be resurfaced.

Now it depends how much material needs to be machined from the head and if the head is warped in any way. Most time you can compensate with a thicker cylinder head seal, but if not the struggle begins, because than you have to reseat the valves, sometimes adjust the valve length and so on. Good thing on a M96 engine is that you can adjust the cam position / timing.

So before doing anything else first step is to do measurements and check if everything is straight.

Hope this is helpful.

Regards, Markus

Hey Markus, thanks for the useful tips, I`ll do the measurements soon.

Best,

Greg

[Homeoboxter]

At last I found some time to work a bit on the engine. As a replacement of the original dual row IMS bearing I decided to go with a roller bearing designed for higher speeds and higher radial load. For thrust control I`ve thrown in a simple ball bearing that I had machined to fit behind the roller. It`s a 2T scooter crankshaft bearing with C3 clearance to bear high temperatures.




Together they are just as wide as the original.



I had a groove machined on the outer ring to fit the original snap ring.

[Homeoboxter]

The whole unit is submerged in oil normally that I think is sufficient for lubrication. However, oil has to find its way around the IMS that spins in the engine case.





Here`s a closer view. At high RPM and at certain viscosities much of the oil may be scattered off from the shaft due to centrifugal force. This may increase the chance that the bearing is not amply lubricated at all times.



Probably it`s overkill, but to overcome this possibility, I thought a bypass oil channel in the engine case could set the same oil level behind the IMS in all circumstances. So, after a few second hesitation I decided to drill an oil gallery in the engine case. There`s not much room here, so I fabricated a mini drill to do the job:



Engine case wall is pretty thick here, so there`s plenty of room for a little oil gallery.



In situ position. Horizontal lines indicate the oil level at min and max sign at the dipstick.



Oil should easily reach the stationary center parts of the IMSB unit via this hole.



The oil gallery actively contributes to the better lubrication of the IMSB as well: the spinning sprocket generates a high oil pressure in its cavity that forces oil into the gallery and thus the back of the IMS.



Oil within the IMS gets depleted via this small hole drilled on the sprocket.