Stroker crank Group Buy

[Slate Blue]

OK first post, I have been on Rennlist for over a decade and many of you would have seen my posts over the years.

The reason for this post is that I need to buy 2 stroker cranks, the problem is the preferred manufacturer will only make 3 minimum. These are not cheap and will most likely be the most expensive cranks ever put into a 928.

There is a reason for this, I want to reduce as much mass from the crank as possible and make the stroke the largest that has ever been used in the 928. The stroke proposed will be 100 mm or 3.937". I am having a replaceable liner short block made using alloy liners that will be Nicasiled. The displacement will finish up around 7.5 litres. I can supply the short blocks but this is not a money making enterprise and I am not putting anything on the parts for profit. The only benefit I may attain is the discount due to quantity which anybody who participates will also enjoy.

The crank will have key changes to address pitfalls that are inherent with 928 engines and some of the stroker crank setup shortfalls. I am investigating the use of different main bearings. These are Nascar spec bearings that have modern grooving not the "old tech grooving that Porsche used back in the 70s. This will address load carrying capacity and friction. The 928 main bearings suffer wear patterns directly attributable to this overly long grooving.

I am looking at using used Porsche 928 bearings as spacer bearings, they will need machining but they will act the same way as spacer bearings do in a 400 small block Chevy. I do intend to retain the thrust bearing and just groove between the holes which will be roughly 140 degrees which is what you want. The line boring from what I am quoted is not that expensive, a couple of hundred dollars although the cuttings of the recess for the tabs would be extra. The interesting thing about the tabs is that they are not present in the bearings surface like they are in the majority of bearings. Again the next level.

There is lots of other aspects to this engine that have been developed or are in development that will push the power envelop north. I am happy to share the developed parts at cost as that is a win win. A part that may interest folks in the left hand side variocam tensioner.

Currently in development are brackets for the GT3 six piston front callipers and GT3 rear callipers using PFC discs and pads. The dampers are Ohlins ILX 4 way adjustable with remote ride height control and Eibach ERS spring system. The front panels are custom and will be carbon fibre along with the roof and hatch. I have a recent ex F1 aerodynamicist assisting along with an engineer in vehicle dynamics who normally works on Porsche Cup cars but will assist in the setting up of the electronic differential.

I don't want to get too complicated here as really I am just trying to spread the word about the group buy for the cranks. I need to order three. I will take one or two. I am currently building a in between engine. It is a 5.0 litre two valve which I hope will do around 430 HP and low 12 second quarter miles.

Just for the record, the transmission I hope to adapt to the 928 will be the Z06 eight speed auto. The ratios work well with the stock diff ratios and I will be using the Porsche 928 differential in any solution I implement. I believe that is key to a tight packaging solution.

If you have any questions or comments just shoot that at me am am not easily insulted and I am always ready to be corrected but hopefully there won't be too much need for that. I am intending to set a top speed record with the car which is one reason for the build.

[Danglerb]

Good luck, sounds like a lot of pushing of the envelope.

I'm thinking a bit in the opposite direction, cheap. A stroker crank made so that some stock rod would work with a 968 piston in a bored 5.0L block with 2v heads.

Are you hoping for 430 crank HP, seems very optimistic unless you have a crazy high rpm limit.

[Slate Blue]

Originally Posted by Danglerb

Good luck, sounds like a lot of pushing of the envelope.

I'm thinking a bit in the opposite direction, cheap. A stroker crank made so that some stock rod would work with a 968 piston in a bored 5.0L block with 2v heads.

Are you hoping for 430 crank HP, seems very optimistic unless you have a crazy high rpm limit.

With regard to the 5.0 litre engine, where it stands now is around the 390 to 400 HP range. The engine has never been tuned and is way off optimum. There is a new ECU going in which has lots of features but the most beneficial will be launch and traction control. When it powered my manual car, it did sub 5.0 second 0 to 60 mph times and trap speeds of 110 mph. I would hope for the same when it gets put into the heavier automatic. With being able to load up the auto, I am also hoping to stay in the 12 s. The engine is getting more comp and bigger intake valves.

[Slate Blue]

Looks like the order is sorted, if anybody else is interested, the cost is about $5K.