freedog009

Hello, I am a new member and now on my second 911...1991 C4. The car is a mechanical rebuild via a Porsche dealership who was going to use it as an on and off track drivers ed car but program was cancelled.

They state the engine rebuild brought the engine to an estimated 350 HP?? Can this be true?

Following are key mod's:

-Cylinder heads ported and polished
-Super Cup camshafts.
-Cold air intake
-Borla headers with free flow muffler and a reprogrammed ECU.
-RSR clutch and flywheel
-Brakes and suspension include Bilstein Sport Coil overs front and rear that have lowered the car nearly 2"
-18″ 997 Turbo wheels
-Alpina sway bars
-RS Wing
-Continental Contisport 235/40ZR18 on the front and 265/40ZR18 on the rear.
-RS Wing

Thougts?

Bernie

crg53

Welcome to the board Bernie, very nice looking car, best color for sure.
To get 350HP out of one of these engines, you will have to do a lot more (spend lots of $$$$$) than what was done to yours, which would include larger valves, new and better fuel injectors, modified intake and Motec engine management system.
Another important thing would be , "who did the work on the cylinder heads"?
Best way to find out is put it on a dyno, and let us know the results.

Trader220

Welcome aboard... I have seen that car around the net for sale, goodl uck and enjoy it!!


Not with those mods... not even close. Ask em for the dyno sheets. To make 350 hp on a NA 3.6 is not all that simple

springer3

+1. Cheaper to transplant a turbo motor if you need 350 HP.

freedog009

Thank you for you commments. I figured as much and they only represented it on the web as estimated 350hp. I spoke directly to the builder (Sr. Porsche Technician at a Dealership) before I purchase and he said it was closer to 300. I'm amazed at the technology and performance of this 20 year old vehicle.

I'll let you know once I have it dyno'd.

GeorgeK

Didn't the Cup cars use the same engine (and camshafts, bar the assisted steering pulley) as the series cars?

evoderby

The headers/exhaust and cams are good mods to allow better breathing, the 964 heads in standard guise are good enough for 350HP so unless a real idiot has been working on them these won't be the bottleneck towards 350HP.

I can think of two or three things that will:

1) fueling/injector size: you don't mention bigger injectors being fitted, standard items flow just about enough for 295-300HP.
2) flapper type air metering device posing a too large inlet restriction for achieving 350HP
3) valve springs: have these been changed to safely allow the cams to operate in the higher rev range?


9M achieves 325-330HP with standard engine internals, a cat bypass / cup pipe, and a restriction free MAP inlet metering device.......and of course perfect fueling (large injectors) and ignition through their Motec package.

Adding cams, porting and headers should bring 350HP within realistic reach...

Geoffrey

The 964 Cup cars run a basically identical engine to the plastic manifold equipped 964 street cars with the exception that the weight tolerances are tighter and accomplished using hand selected parts. The engines are not "blueprinted". However, I'd bet that you'd be hard pressed to find a factory assembled 964 Cup engine these days, so the point is basically moot.

freedog009

Thank you for the reply. I checked the rebuild documentation and find the following relevant to your points above.

1. No..Injectors were cleaned but larger injectors were not installed.
2. No idea about this
3. Yes, all valve springs were replaced

They did replace the ECU but I'm not sure if it was a MOTEC or not. Documents show parts cost of $450.00 for the new ECU.

boxsey911

Welcome aboard....the car looks great (except for the wheels )

crg53

To replace the ECU with MOTEC would cost thousands of $$$$$. $450.00 is about the right price for an aftermarket chip. I.E. www.911chips.com
Did the bill specify which type of valve springs were used?

GeorgeK

Do you have a dyno day planned? That would tell the tale.
Prepare to be surprised though. I'm betting on less than 300HP.

freedog009

Cheap shot on the wheels but I did see you're from GB so I understand..HA!

Seriously, I think they look great but there are a lot of great options out there for rims.

freedog009

In the Spring...I'll share the honest actual documentation when finished. It will be interesting to see how much beyond stock the extras took it and how many $$ per HP that cost??

freedog009

Gotcha...nope...the documentation just stated 12 springs. The guy who built the engine is a 31 year SR Porsche Technician (came over from France) and he specializes in rebuilds; so I'm HOPING, I'm reallly hoping....that he put the right springs in....what kind would have you used?