BC

I walked in and was like “that’s a GTS”

Why does it have a....

Wait, is that a dry sump Box?

WTF Greg?

GregBBRD

Chrome Moly Billet Limited Slips.

The GTS oil pump is completely part of the rear differential cover. That cover will fit onto an earlier transmission. As a matter of fact, the early GTS transmissions with the oil pump were modified '90/'91 transmission cases.
You will need the banjo bolt and the return line, as well as the spray bar on the driver's side (where the case needs to be modified.)

GregBBRD

You weren't supposed to see that....nor be intelligent enough to know what it was you were looking at. (It's normally covered.)
Besides you, Mark Anderson, Rob Edwards, Russ Tyler, and Rob Dickinson are the only ones that have seen and understand what is going on, there. (Besides the car owner.)
Although Rob Edwards has seen more of the small details....I don't think he's taken any pictures.

Tom. M

thanks for the info...very interesting...good to know that the pump can be fitted too.
Following this thread now

Rob Edwards

No pictures of the special sauce!

IcemanG17

I would guess this GTS will need bigger brakes as well...... 700hp and say 3400lbs on track will need serious brakes

GregBBRD

Yeah...but perhaps not as much as one would first imagine.

The first thing to realize is that the stock 928 braking system is far from optimized. The rear brakes do work, but not well.
Just the ABS system, controlling only the rear wheels as a pair, is an extremely old design and keeps the rear brakes from properly functioning.
A pressure regulator and ABS is like telling the rear brakes "Thanks, but we don't really want you to do anything."
And a limited slip, which starts doing its job only after the braking and the corner are actually part way through, makes for....interesting braking requirements.
Add in a super trick set of shocks and associated pieces and braking requirements begin to change.
And understand that this car will be run, consistently, on "fresh, sticky, rubber"....not on tires "rescued" from a dumpster. This alone will make a huge change in any car.

My target is to build a car that is extremely well balanced....with everything working in harmony.

That means I'm improving just about everything on this car. Very few things, except the body and most of the interior will remain original.

Patience. I'll "get you up to speed", as time permits.
It's a very involved project.....

Ducman82

Well done boss! Glad you are still inventing!

GregBBRD

Like a mad man!
You'd love this project!

Petza914

Greg, this is very cool.

To solve the transmission torque problem, why not use the C5 or C6 Z06 setup that already has a decent limited slip integrated into it and can withstand in excess of the 500 HP those cars produce in combination with your new clutch. Other than the the shift ****, looks stock enough from the inside except for that extra gear in the pattern of course. For a higher HP build, those ratios are actually quite well matched too and the carbon fiber synchros hold up and work quite well. Just curious.

GregBBRD

Great question! I'll try to answer it, without passing judgement, but just being truthful about my personal reasons.

Two BIG reasons:
1. In my younger days, I spent many years, playing with Chevy engines in Porsches. I had a Trans-Am 302 Chevy in my own 67 911. Crazy fast. You could leave the pits, at Riverside and pull redline in 4th gear, before turn 2! It would pull 5th gear to 8,000 rpms down the back straightaway at Riverside.....180mph! (Stock geared 915 transmission.) The tach stopped at 8,000 rpms, but this crazy engine was still pulling, so I'd count slowly to "3" and shift it. Fastest track car I've ever been in! Had more fun than any human should have at Riverside, Ontario, Willow Springs, the old track at Laguna Seca, with that absolutely insane turn 2 curve at 150mph.

To this day, I have no idea how my best friend and I "lived through" this car!

I had 3 really long time, good friends with Chevy's in their 914's....one was a 780 horsepower twin turbo 350. I put in several Chevy engines in client's cars...one was a spanking brand new '79 930 that I put an all aluminum Donovan 350 in!

We were the "bastards". Couldn't run at Porsche track events...had to run with the Cobra Club at their events. They disliked us. Could drive right by the very best of the 427 Cobras.
We could also run at Solo 1 events with SCCA. They hated us. Nothing could complete with us. My own car ran in "A Sports Racer"....a catch all class for everything too fast to run in any other class....mostly old Cam Am cars, etc. No contest.

And then, my own car had a terrible crash at Willow Springs, with Rod Simpson (the "father" of the "Porschev" movement) driving it and Lynn Park, then president of the Cobra Owner's club riding...left turn 8/turn 9 complex at 180mph. In those days, some drunk had had gone across the desert in an American car and killed himself on the track at night. The solution was to build giant "berms", out of dirt, to keep people from being able to get onto the track. These turned out to be "sloped launching pads" from the track side. The car went ~100 feet straight up, doing "door rolls" and came straight back down, landing hood first in the berm. Rod Simpson's father (just retired from the Califonia Highway Patrol) and my really good friend, Jack Murphy, were the first ones to the crash scene. They parked their car on the track and started running the 150 yards to the car, when Rod's dad grabbed Jack's arm, stopped him and said: "I've been to thousands and thousands of crash scenes, in my career. Prepare yourself...there's no chance anyone is alive in that car."

People's lives were changed forever, on that day, although both guys survived. They survived because there were two paramedics watching the Cobra Club Event (no safety/rescue people/ambulance required at the track, in those days) and those two guys rescued those two friends, got airways cleared, revived them, and got them stable enough to transport to the hospital. Altered my friend's lives, but they lived.

I didn't even go back to a race track for over 15 years!

And when I did go back, I was over "hybrids". From then on, I put Porsche pieces in my Porsches and Chevy pieces in my Chevies, so that I could race at events where there were safety/rescue people....Porsche events.

2. I have yet to see a Corvette transmission swap "kit" that didn't require a major amount of rework to make it "nice" and completely functional. (I looked at what Sterling was going through and just shook my head.)
In my old age, I've completely lost patience with the "unsavory" people involved with Porsches....I'm tired of the cheats, the liars, the people who blatantly and openly copy pieces, and the people that make poorly engineered pieces.
I just didn't feel like buying something that was supposed to work....and then having to take those pieces and completely start over.....I'm really tired of solving other people's poor engineering.
And I'm so involved building super trick 928's for people who want to use all 928 "assemblies" I didn't have the time or interest to maker these conversion pieces, on my own.

Plus that, I'd violate my own rules, my own moral standards: Never copy, even if you are improving, someone else's product!

As a matter if fact, during this period of time (when I was "watching" the whole Corvette transmission fiasco unfold),) I had an "open budget" 928 sitting in my shop. Build a big, crazy stroker, make it handle and stop....very similar to the project that I'm talking about on this thread. However, the owner insisted that I install a Corvette transmission. I kept "pushing it back in my schedule, making excuses; waiting to see if the entire concept was viable.
I finally had to "pass" on the project and sent the car...away.

I hope this helps you understand my reasons!

















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SwayBar

Firstly, I don't need any steekin' pictures of the car, I am sure it is a jewel just like your others.

Secondly, great story, appreciate hearing more of your background!

Now, after all these years, there are two outstanding items with the larger displacement 928 32v - intake manifold and manual transmission.

Firstly, mating a C7 Z06 transmission to a 928 is not copying anyone's work, and is a viable alternative to the 'wimpy' 928 manual, and would be the logical choice and work like a charm. On the other hand, no matter what you do to the existing 928 manual, the gear-sets etc. will still be the same, thus too small, for a larger displacement engine.

You can solve both the intake manifold and manual transmission conundrum in one fell swoop:

Keep the engine at 5.0L, and install ITB's like Alex/Cheburator and John Gill - their cars dyno'd at 435 and 450 rhwp respectively. Those numbers are WAY bigger than any of the large strokers with the stock intake.

435/450 rwhp is stupid-fast for any track car...

Additionally, with the ITB 5.0, torque is down, and horsepower is up in the RPM range, like a real race car, which is much easier on the transmission compared to the all-torque engines. Therefore, the stock 928 manual transmission, along with your tricked-out diff, clutch, synchros, etc, will probably last forever in the ITB 5.0 - and one less thing for the owner to worry about.

For the hardcore performance guys, an ITB 5.0 and manual trans would be a nice, reliable street-fighter/track-car, and would be the ultimate 928 for those types of guys - and at a lower cost since it's a stock block.

Summarizing - a 5.0L with ITB's can continue to run the stock 928 manual trans reliably while putting down 435/450 rwhp.

And your big displacement engines with the stock intake and automatic trans is perfect for the pure-street guys, and they'll continue to be happy.

GUMBALL

I am curious, in regard to transmissions, have you looked at a Hewland or an X-trac ??

Advantages:
- wide selection of gear ratios and final drive ratios
- selection of limited slips . . Torsen, Quaiffe, etc
- models available to take ANY horsepower and torque

GregBBRD

I'm not convinced the GTS transmission is inherently weak...the gears and pieces
are actually very robust.
I've been doing this long enough to know that transmission life is completely determined by the driver. (And granted, I have zero idea of how the owner drives.)
If the transmission turns out to be the limiting factor, I know that there are options.

In the beginning, we're traveling this path, but we will do whatever we need to do.

As I mentioned, I already changed the stroke, the bore, and the displacement to reduce the torque. And the donor engine had ITB's with aggressive cams.
Additionally, the new headers and exhaust are designed to move the power range higher in the rpm range.
Maybe I can get enough air through the engine to run it to 7800, or around there. Keep in mind that Andy's original engine made peak horsepower (605), at 7200 rpms.....And it wasn't done. There just wasn't any reason to go any further. As a matter of fact, we didn't even bother tuning it above 6500 rpms....whatever it did, beyond this, was moot.

There's been a plan and a method in my madness, for this new car, all along!

jetrainor

15 years ago i installed Constantines 'clamp' on the splined shaft of my 87 after suffering Thrust Bearing failure and replacing the engine with a new to me motor sourced from a 5 speed car.....a recent check of the flexplate shows zero movement....super peace of mind fix for flex plate worries.