Ok, that's nice, but why keep comparing the Cobra to the 928. Wouldn't the Mustang GT be more on the same level with the 928?

The Cobra Rs was a flop from Ford. Only 300 or so were made an the hype was huge before the car came to market. The Z06 was released in the same year and blew the doors off the R. I remember reading all about it in every car magazine. Even the hard core Mustang fans were disapointed. I mean, what the heck was with the " you need a racing liscence to buy one" and came with NO warrantly, no AC...basicly nothing at all. On the other hand the Z06 was fully equipped and with a factory warranty and the price was alot less.

I had a Mustange before and even put a supercharger on it, but it never even came close to the feel and enjoyment of the 928.

 

I'm not trying to compare the car, because that isn't even fair. The 928 wins hands down. I've had both and liked my 928 WAY more than my GT. I was just comparing head flow, nothing more. I just think that putting a different power plant in is a different way of making power, just different. It doesn't make it not a 928 does it? If I were to do a swap, I would do basically the same thing Patrick has done and enjoys.

I don't think the R did well for the exact reasons you pointed out. Considering if you wanted the same performance you could just buy a '03/04 Cobra and have all your creature comforts and a warranty. Not that they were out at the time, but there were enough rumors around that you could think that it might happen and did. How about the Camaro that's coming for what 2008? That looks like fun...

Jon

 

The Cobra R was a homolgimation special sold only to qualify the car to race in speed GT against Anderson with his 928 and others just like the old Boss 429 they had to sell some to get the engine allowed to race. Ford only wished to sell the 300 and had no desire for that car to be used on the street.

 

Jim,

Thanks for clearign it up. I only knew part of the story. The only thing that realy bugged me back then was, why was it necesary for Frod to sell the Cobra R for buyers that had a racing license? After all, the Cobra R was street leagal. Why is to create hype or something more?

 

I've got a 69 chevy dz 302 that was a spare motor out of a trans am series z-28.It,s built to 950+ hp and 850 + - torque.I've built it to put in a 67 Porsche.I started looking in here for a trans to use.I'm considering a Getrag G 50.The 901 in the car now is trash.It,ll be a 7500 to 8200 rpm motor.The motor is built for a high rev endurance motor.I've got two TO4 turbo,s in it nowm having a terrible time making the intercoolers fit and controlling the heat in the engine compartment of a plastic car.If you want to know about the motor,It,s balanced,decked,blueprinted,dipped,etc.Bored to 4.030,6 inch bushed steel h-beam rods,polished forged Callies crank,210 cfm AFR Comp 3/4 deck aluminum heads.2.08 valves, Jesel shaft mounted rockers.Solid roller lifters.The hydraulic rollers couldn't keep up with the rpm,s,even with a rev kit.Using 6 inch rods to put the pin close to the crown of the pistons to eliminate any slap.70cc chambers,-20 2 relief forged pistons.Comp ratio is 8.3 to 1 mol.Trying a Whipple supercharger this week,don't think I'll be happy with the boost.May switch to a Weiand 142,Model 7740 high rev. blower.Has thicker case and shafts for revs.Anyway,I,m pretty sure the turbos have to go.Between the radiator,exhaust,intercoolers oil coolers,etc,I've run out of real estate and my fuel tank is getting smaller and hotter.If you have any ideas about transaxle let me know.

 

Bumping this old thread as I'm wondering what the factory 928 transaxles (5 speed or auto) can handle in regards to hp/ torque. I see chevy conversions and also forced induction Porsche engines making 400+ RWHP. Do the stock boxes live with this?

 

Stock auto boxes are very stout and take 500 hp no problem, some are even taking 900 without a hitch. Albeit those have refreshed internals.

Manuals are more delicate and you would need to upgrade the clutch and then you shouldn't put more than 450 hp through those to be safe as parts are very hard to find for them.

 

I have about 10,000 miles of ~470 crank hp running through a dual disc carbon clutch and a 5-speed GTS box, haven't broken anything yet.

 

That's better than I had expected on the auto. Thanks!


Rob, is it safe to assume the GTS uses a more robust 5 speed than say an OB 78 - 86 for instance? Or are they similar? I appreciate your feedback- Thank you.

 

So...where exactly is this "450 hp" figure coming from? Seems a bit arbitrary. How a car is driven has just as much to do with the life of the transmission as the power output. People with stock engines have ripped through a stock gearbox, mostly at the track.

Run a stock 928 down a drag strip with the sticky goo & slicks, and drive it like an Hurst Olds 88 it's not going to last very long, even with a stock US 16V motor.

Street car, DE, full race, drag strip, weekend burnout queen.......

Cooling is an issue with these boxes, there is none. At least the early units, not sure about the later years.

Todd's twin turbo survives not only because he went through it, but also due to the extensive tuning on how the engine behaves when it shifts.


Torque is also the bigger culprit when talking about transmissions longevity, not HP.

 

Gave up on trying to find 400 HP naturally aspirated. Started looking for 507HP as the market crashes on them..

 

From the standpoint of looking at the gearsets, there are basically 4 generations of 928 manual boxes- 78-82 (G28.03 & 05), 83-84 (G28.07 &8), 85-86 (G28.10 & 11), and 87-95 (G28 12/13/55/57). The 1st two generations use the Porsche synchros, the '85-95 use Borg-Warner synchros. The 1st three generations all use a smaller input shaft bearing, The S4, GT and GTS boxes are all the same from a gearset standpoint (though the R&P's are all different), but the GTS box has two important differences- It has a hollow pinion gear shaft for oiling, and it has a gear-driven pump and an external cooler that sits on top of the AC condenser up front.

Depending on what RPM you want to be turning at your preferred highway cruising speed, any of the later boxes should stand up to street use just fine.One could always add an external cooler and pump, somewhere I have a rear cover with fittings and a pump for this.

The issue isn't the gearbox as much as it is the clutch. A dual disk with an upgraded pressure plate is good to about 375 rwhp, above that you need to move to a Spec clutch or a carbon clutch.

 

Great info, Rob!

Safe to assume that in the 85 - 86 model years that the US and Euro cars would have the same trans? Also, I assume this makes for easier to source parts in the event of a rebuild? (85 - 86)

Thanks, Steve.

 

The 85-86 Euro vs. US market differ in their final drive ratio- 2.73:1 vs. 2.2:1, respectively. Otherwise the rest of gear sets are the same. Here's a table of all the major components of the different 5-speed boxes, so you can see how the individual gearsets 'cluster' across different transmission types.