Underdrive Pulley Install Guide

[jmatta]

Thanks for the write-up, as this is a mod I'm currently considering (always need a spring project). Anyone know what the protrusion is for, that needs to be milled down? Almost looks like a point where a bolt would go to lock the pulley (not sure it lines up)...it must be there for a reason.

[JFP in PA]

It could be a couple of things; the M96 is used in multiple configurations, so it could be a mounting boss for something not use when in a Boxster. A lot of casting bosses on these engines are used as anchor or alignment points during initial machining operations in the factory, and not used again.

Considering its location so close to the factory pulley, it probably is not used when the engine is actually in the car.

[Topless]

I believe jmatta is right. The boss in the casing that must be cut down is a top dead center locator. You align to TDC and slip a retaining tool through the stock pulley to hold the crankshaft in place. It is useful when changing timing chain tensioners to keep everything aligned so don't cut it all the way off. There are other ways to fix the crankshaft at TDC but this is a quick way that techs are familiar with. On one car in our club the casing boss was completely cut off and the Porsche techs had to get creative as they could no longer use the tool.

[clickman]

Fig. 25 confirms it's for TDC.

http://www.pelicanparts.com/techarticles/Boxster_Tech/Disc163/BoxsterTech-163.htm

[jmatta]

Very good visual, indeed. Do you think the point is strong enough to hold so you could loosen the crank bolt? The only experience I have is that is remotely close is the tool that holds the pulley for removal in an older air cooled 911.

[TroyN]

It is strong enough. The bolt is on there way tighter than the fan/alt nut on the air-cooled 911s incidentally. (just did this mod today)

[CapDunn]

Why not remove the stock pulley with air tools?