IPB-Autosport 996 GT3 4 Liter

[FTS]

Side by side the difference is dramatic, super pics, thank you.

[FFaust]

Pity to hide those parts on the "inside".

[IPB-Autosport]

Guard LSD parts arrived. Let’s go.

Ring gear comes out.




Time to split the housing.




Out come the guts.



Oops. Serge's beer gets in the way of our photos.



This measurement determines the thicknesses of the friction disc spacers to achieve the correct preload.



Spider gears.



Guard rebuild parts.



OEM vs Guard.





Friction disc spacers.



Belleville washers. You can see that the Guard parts have more curvature and greater thickness to achieve a higher spring rate.



LSD is held in place with the aid of the output flange and a vice. We actually had to fix the upper flange as well to achieve the 148 ft/lb required. Although, the preload alone almost did the job.




Rebuilt unit.

[TRAKCAR]

Thanks for posting. Now I know what it all looks like ..

[FTS]

^^^ +1, excellent thread and documentation.

[kristap]

Thanks for documenting like this!

[IPB-Autosport]

Christmas came early! What do we have here…



997 Cup heads!





997 cup intake port.



996 street intake port.



Close up comparison.



Exhaust side.



997 exhaust ports.



996 exhaust ports. Not much to see here…



Side by side.



Parts for a full engine rebuild, including the oversized gaskets for the 4 liter.



ARP rod bolts, of course.

[PJS]

Subscribed

Chubby inducing thread

[FTS]

Ron, this is superb, the comparative pictures are so clear and self-explanatory that I cannot get enough, just superb. Thank you for this post, documentation and explanations, very much appreciated.

[IPB-Autosport]

The machine shop.





They do a lot of work for Flying Lizard Motorsports. When I was picking up my parts, he was modifying some RSR sway bar arms. Here are some brake hats in process for the Lizards.



The machined case. The sleeves extend about an inch into the case so it had to be opened up for accommodate the 4.0 liter sleeves.




Here’s the cylinder head and case mated together. The machining process was such that it provides a seamless transition from the cylinder housings to the case.




4.0 sleeves are test fitted.




Here you can closely see the finish of the Nikasil coating on the cylinder walls.



While waiting for the machine work to be completed, the coolant pipes were welded. As many of you know, the glued pipe interface has become a well documented Achilles heal of the GT1 engine. The welding isn’t going to win any beauty contests, but is functional.

[FTS]

I hope this is not a stupid question, but Ron, do you have a target compression ration for this at this time, or will that be determined at a later time during tuning? I am trying to understand how the compression ratio targets impact the design, and later on, the details of machine of the case.

[IPB-Autosport]

Compression ratio will be increased at the rod/piston connection: the wrist pin. Since these wrist pins have a smaller overall diameter, this allows us to offset the hole in the wrist pin bushing. This bring the piston further up, reducing the volume of the combustion chamber. The target is 12.5:1.

-Serge

[csmarx]

Nice project! Wonderful to follow along with all the pictures. Thank you!

[IPB-Autosport]

Rods are in.




New rod bearings.



Everything lubed.



Assembly time.



New oversized bushings to accommodate the 21mm wrist pins.



And the engine build is on its way…

[FTS]

Very interesting; what kind of inner sleeves are those on the rod bearings?