DC90 cams? Yeah at 8500 RPM, I'd be shocked if you didn't see 275HP at the crank. All of those little detail bits are going to pay dividends.

So, undergrinding the crank for GT3 rods...I assume the spacers are to compensate for getting the deck height right?

The spacers have nothing to do with deck height. The GT3 Gen II rods are the same length as 2.0-2.2 rods 130mm. This means that the cylinder height is standard at 85.smm when used in concert with RS pistons. Stock cylinder height, stock rod length, stock pin location means the deck is predictable at .040-.050".

The spacers are designed to return the cam tower to their original location after the heads were decked to create additional compression. The chamber volume needed to be reduced in order to run the relatively flat top piston. The reduction of the chamber volume has limitations. Valve shrouding is the issue here.
By filling the chamber you are faced with a choice. Reduce volume size too far and the valve becomes overly shrouded causing reduced flow. Enlarge the area around the valves and the compression goes down. In this design opening the area around the valves forced the need to mill the heads. Milling the heads creates dimension issue with overall engine width. To maintain the dimension integrity of this engine the dimensioning shims become the best option.

I assume you can buy the Gen II rods at your local friendly Porsche dealer for a kidney and 2/3 of your soul? ;)

You'd be surprised Kenik, pretty cheap actually. I don't use them but I've priced them.

GT3 Ti rods
 

Ballpark $$ ??

Even better, part numbers so I can call my dealer?

new $3,000 or so and good rebuildable set $1500 = or - some.

996 103 012 88

That rebuildable price is pretty bloody compelling...

Yeah now I need some for a 3.0 crank

Hi Ben
Gen I GT3 rods have the same dimensions as the 3.0 rods. They are 127.8 mm center to center and 22 mm wrist pin bushings.
There is good new and bad news when it comes to Gen I rods. Bad news is they are even more expensive than Gen II. The good news is that I have a set or two of these rods in good used condition.
Lets make a deal.

Dumb question number 5287 for Henry or any other of you great engine builders out there:

How does one determine what an engines RPM will or can be? I mean from a physical standpoint, how do you know at what RPM will tear a motor apart without actually doing it?

for example: You hear people rebuilding an engine for racing purposes (Or street for that matter) and some how they seem to know it can now do ...say, 7500RPM. instead of 6200.

To be honest with you the majority of the constructors will run the engine around 500 to 800 rpm higher then peak power to get the largest area under the HP curve. Then they will address what breaks. Factors include weight of the piston and piston speed, strength of the crank and resistance to bending,same for the rod. Then the upper end and its challenges such as valve float etc. . A lot of research in materials has led to the establishment of engineering criteria that etablish benchmarks and limits such as piston speed valve trajetory etc.

regards

Nice looking engine but why did you decide to that rather than using a Mahle 89mm p+c set which has a compression ratio of 10.3 to 1?

There are 3-4 threads on this. Basically the domed pistons shroud the flame front, causing detonation, limiting usable CR. The heads with flat pistons create a better squish band with no shrouding. Thus higher usable CR without twin plugs.

This engine is an experiment concerned with chamber vs piston shape.
Hemi heads have been problematic since their inception and this project looks to move the air cooled flat six Porsche platform to a new place.

Building the same engine over and over again and expecting a different result is tedious and perhaps a little crazy. We have been building the same old air cooled six for some 30 years and when we were faced with a slightly new direction, we jumped at the opportunity to experiment.
Many of you are experimenting with Varioram, EFI systems, turbos, 4 valve heads and water cooling. None of that interests me. So that leaves me with few places to experiment. We already build a nice distributor to ignite the package. Volumetric efficiency modified by port shapes, chamber shapes and dome configuration is where we are playing now.
I have great guys to bounce ideas off of and the luxury of parts and time to play.

It looks like a socialistic government (Obama) is coming and money will become scarce, so it's now or never.

Sweet looking engine Henry!

These threads make me cry.....I look at the pictures of engines as pristine as these then think back to the level of presentation I managed with my rebuild and cringe.

I did not cut corners on the cleaning process or the preparation......it is just at a different level!

Thanks for sharing the dream with the rest of us.....!

Henry,
Does that mean the gen 1 GT3 rods will fit in a carrerra 3.0 motor??

Michael

Sorry, they won't. The 3.0 Carrera uses the same connecting rod as the 2.7. It is the same length but the big end of the 2.7 is wider than the 3.0 SC and GT3 rod.

How did the dyno results turn out?
Or is this still a work in progress?

Doug