Reason
After a roller coaster diagnosis my engine warrants a rebuild. I've passed a lot of time thinking about selling or rebuilding and the costs. After a lot of confidence boosting from Rennlisters I have finally decided to keep and pursue the ultimate goal. You lot were right, I'm shy to admit/ confess the car's not going anywhere and It seems I was always to rebuild.

Thank you to all who have given advice/ support and quotes. I'm still deciding on the builder and will of course thank those who took time to quote me when I've made my final decision. I believe most will understand that receiving many different quotes/ options is a responsible undertaking when considering the considerable cost of any venture.

The reason I'm posting this is to further my knowledge/ receive help in specing my engine rebuild. It's not every day one rebuilds one of these engines and I feel I owe the sum the respect it is due by carrying out extensive research and seeking advice from the great experts we're privileged to have here.

Purpose
I use the car mostly for track days, long weekends and continental drives. Comfort is not an issue for me - (I run my KWV3s on full hard all of the time, in hindsight I would have gone ClubSport) what is important however is reliability. I'd like the engine to run for another 100,000 miles. Noise is also not an issue - I read 105db static... wasn't an issue at SPA or Donington.

So you have an idea of how I use the car: it currently has a LWF, RS clutch, Big reds, ducted brake ducts, 18 inch wheels 8.5 and 10 with track rubber. The car is a C4.

Why not rebuild to standard?

1. As it stands the value of my car has taken a big hit with the fact it needs a rebuild. Building back to standard will bring the value just north of where it was pre engine trouble. Therefore I would see less money back. Where as If I rebuild to a higher spec the value will increase a lot more - obviously not by the amount spent but closer. I appreciate completely that modifying cars is not a money making exercise by any stretch of the imagination and one should out of pleasure first and foremost. Besides I don't comprehend selling the car - especially now that I'm rebuilding.

2. The prominent reason I want to is because I had always set out to modify with a vue to increase HP. It seems it makes the most financial sense to do it now when the engine warrants an engine rebuild than have to work back later.

Rebuild specs
Here is my theoretical spec I would like advice on. Please bare with me as my knowledge of engines is rather limited.

* 3.8 Barrels & pistons. As I understand it, Mahle P&C are the way to go for an engine that will last. I hear JE pistons are more appropriate for race cars that are rebuilt after 100hrs of track use. As I understand it a 3.8 upgrade is done for higher torque values as opposed to horsepower gains. Capricorn P&Cs?

* Forged connecting rods. Corrillos seem to be the popular choice. Seems appropriate for an engine that will run high rpm, possibly ITBs.

* Cams. I'm still not sure what cams would be suitable? RSR/ Cup/ Shrek/ 9M?

* ARP or Corillo rod bolts? ARP head studs?

* Stiffer valve springs and titanium retainers. Uprated valves & guides? RSR valve seals?

* Intake. 993 Varioram, FVD hot film kit, or dependent on budget ITBs - PMOs perhaps?

* ECU. Standard remapped Motronic or Motec/ MBE/ Emerald if ITBs are used.

* Exhaust. I'd like to stick with my exhaust setup for the time being: Cat-bypass and G-pipe.

* Cylinder heads, presumably these would require modification to accept some of the aforementioned - if someone could chime in with specifics please?

* Replace bearings. Jerry Wood/ Smart racing products?

*GT3 Oil pump.

*RSR Rocker shafts seals to help against leaking?

* Reinforced engine carrier and solid engine mounts?

Big thank you to all who have provided great posts/ threads - they have provided great insight.

TIA

 

I've done a number of these engines and Colin at 9M would be the one I'd call if I were in the UK. The varioram intake will produce the most broad torque range and will have 35ft/tq in the midrange over the plastic intake, although it does make working on the engine in the car near impossible. I'd stay 3.6l for durability, and a properly built 3.6l piston will produce more power and torque than the RS 3.8 piston. Carrillo rods or Pauter rods are work well for what you want to do. Use RS valves in 8mm with good springs and a light port cleanup to maximize performance.

A performance engine with proper mapping will cost more than a stock 964 is worth...so be prepared.

 

Wow that is one expensive wish list! As Geoffrey says the cost of doing that will be more than the value of the car. More to be gained by weight loss and some basic tuning imo.

 

Frank:

I can't offer an opinion but I will watch this thread closely. I'm in the same boat as you - the car will never get sold. But I will have to rebuild at some point.

My wish is to drive the car down to Racetek and get the full 9M treatment one day (hat tip to Geoffrey). But I'm open to other alternatives.

I have exchanged emails with a company in the US that is interested in talking about re-gearing a C4 box. My understanding from Kai's recent threads on transmissions is that a re-gear (2nd - 5th?) makes a tremendous performance difference too. Let me know if you want to go down that road too!

Good luck.

 

Hi Geoffrey, Thank you for the reply. Would ITBs not produce more gains than than a varioram intake? Would properly built 3.8 pistons not produce more torque? What in your view are the gains/ pitfalls of 3.8? What P&C would you use for reliability?

Thanks in advance and for bearing with my limited knowledge.

Cheers, do you mean RedTek? They are also on my list of potential builders.

 

+1 on calling 9m....

Take a look at Kaib's thread on his engine - they got enormous hp and torque out of a 3.6 motor. Sounds liek that route may be less expensive than the proposal above...

I'm glad you chose to rebuild - My feeling is that I could buy a new 911 every four years (Or audi, or any car) just like my friends do, trading them in and buying again...but why? I have the car I want, and rebuiding it once in a while is still less expensive by far than continually buying new cars every few years...

good stuff - let us know what you decide (I'm sure you will)

 

One thing I would have to say is that whatever you do, make sure you have the complete oil circuit including oil lines and oil coolers completely flushed and professionally cleaned. I read several stories on PP where a newly rebuilt engine gave up early due to debris still in the lines and coolers.

If the debris are still in the lines/coolers, they can clog up the spray bars on the new engine and cause the same problem all over again.

 

Geoffrey's company is called Racetek Engineering. He's a few hours away from me in New York. I think he's the closest supplier of Motec and 9M stuff for us Canadians.

 

From my understanding the above setup including ITBs could translate to circa 350hp crank. I understand this can be achieved with 3.6 P&C but torque is increase with 3.8 as my understanding goes.

I'll investigate...

I have spoken to Colin - who was as expected, brilliant. As said, I am understandably considering many quotes/ options.

Agreed.



Very good point. The oil lines/ cooler was replaced very recently... the system has been flushed and filters changed twice. I have a feeling that will happen again.

 

As broad a view as possible before dropping the cash. Probably worth calling the other usual suspects JAZ, Autofarm and JZ.

I would also try AP Design in Germany.

 

Glad youre keeping it Frank, after all our leader cant defect!

Not sure what route I would go down but I think I'd have a chant with Grant, we know just how quck his car is!

 

9M !

 

Frank:

First of all, thanks for the , it's much appreciated.

On the face of it, building a 3.8 engine is a piece of cake and as you are already finding out, there are many companies willing to take your money and put one together for you. The downside is that there are also many companies who will give you great advise, buy expensive parts, put them together perfectly - but not achieve close to the results that you expect. Don't get me wrong, there are many ways to build a 964 engine that does perform and the magic ingredient that a parts shopping build seldom includes is synergy. I can't speak for others (apart from Geoffrey) because I have not been involved in the test processes that they have employed, however from my simple engineering perspective there are key decisions you can make which ultimately lead you to the build options that make sense and give you best bang for your buck, as our estranged cousins so eloquently put it.

Decision 1: RPM limit
The two choices here are up to 7000rpm or beyond 7000rpm, period.

Below 7000rpm you can use stock crank, oil pump, rods, pistons, intake systems (964 or 993 varioram) & exhaust. You rework the heads to work with your pistons & intake, select cams which work with the intake & exhaust and fit an engine management system which gets the best from the combination. ITB's on an engine to this spec are not recommended (by 9m) because the lack of cross-resonance tuning will lose a significant amount of torque in the mid range compared to a nVR or VR manifold.

Above 7000rpm the stock rods & pistons are overloaded (due to G-force at overlap TDC), the stock intake system chokes and the stock heat exchangers interupt high speed scavenging. Hence you would build the engine around an ITB set up with long duration race cams, race pistons with valve pockets and a suitable set of headers. Running ITB's means that the Motronic has to go (unless you programme a 993 system to run without the AFM) which is where Motec* will be required.

*or equivalent system

Next choice: Stock engine management or Motec?
I've probably tested over 100 964's on our dyno over the years. The best result we have ever seen from a stock 964 Motronic system is 311hp which was on a 3.75 litre running a MAF (hot film) conversion. The best I have seen from a stock 964 3.6 running a stock AFM and airbox is 306hp. The limiting factor is the size of the fuel injectors and (in my view) speed of control of the system - stock injectors will support 300-310hp and that's it.

A stock 964 fitted with a 9m Motec* system regularly sees over 325hp whereas the 964RS with blueprinted engine and LWF usually makes 330hp, although very occasionally we have seen 335+bhp. This is a stock 3.6 engine, remember. In other words, it is pointless attempting to tune a 964 engine beyond 300hp unless you address the fundamental fuel delivery limitation of the stock Motronic installation. So, picked Motec*, what's next?

We're back to the rpm limit choice.

For a sub 7000rpm engine, choose the best intake system for the spread of power you want; go varioram for supercharger like flat torque curve or go with the plastic resonance flap 964 set up for a slightly higher peak torque number and fraction less top end hp. Next pick a cam which will work with the stock intakes; this invariably means cams with wide centrelines and maximum of 2mm lift at TDC if you want an idle. The good news is that these cams will work with stock pistons. When it comes to pistons I would pick stock 964 or 993 3.6 Mahle units for best reliability. If you choose 993 pistons (because they are lighter) you will then need 964RSR rods (Carillo) to fit their narrow pin bosses, otherwise stick to stock rods & pistons. You can add a set of ARP bolts if you want to buzz the engine to 7k, but otherwise stock will be fine (as proven in the 964 Cup cars). Going to a 3.8 is an option, but don't expect huge power gains, just a bit more mid range torque. As for cylinder heads with this combination, light port cleaning, detail seat work & 993 valves give the best results which will be around 350hp. If you're wanting a bit more a set of headers will bump this up to 360 or possibly 370 on a 3.75 litre.

For a 7000+rpm engine, a whole new world opens up. Heads as above or the 9m billet heads is a good place to begin, cams will need much more overlap & duration to get the time-area required for cylinder filling at high rpm, hence ITB's are best for the intake. Since the cams will have more lift, piston pockets are required so you may as well choose 102mm race pistons & cylinders. Rods will also be required as the stock flex over 7k, so again pick from a list of Carillo, Arrow or Pauter; the rich may choose a set of GT3 titaniums & matching crank & pump but it is not essential if you keep below 7700. Headers are pretty much essential to get everything working well, so don't expect warm feet in the winter, but for your sacrifice expect to see north of 400hp.

So that's it. Don't believe anyone who tells you that you can have more than 310hp on stock injectors. Be very sceptical about 360+hp claims from engines with a stock intake, and finally don't believe anyone who says that ITB's are a good idea on a stock rpm engine.


Hope this helps you enjoy the ride Frank, just please avoid those potholes as some of them are big ones!


Footnote:
Had a call today from a new 964RS 9m Motec owner from Silverstone. He had nothing but praise for his new 9m M84 conversion, amazed at the flexibility and bottom end grunt that we have added along with the much improved acceleration. Quote: "there's a guy here with a red 3.8 964RS who's convinced I've now got a 4 litre engine. It's not just faster than his, it absolutely leaves him for dead. Please thank the team for me will you, I'm now falling in love with this car all over again....."

 

Hi Colin,

Thank you very much for taking the time to write up the aforementioned - you have truly been great help and a gentlemen. Appreciated.


EDIT: Would I be understanding correctly that for under 7,000 rpm ITBs are not beneficial - I also assume that running above 7,000rpm reliability takes a hit?

 

Frank I think the above post from 9m says it all in a nutshell.....

If I was lucky to be in this position I think sub 7000 rpm build 3.6 /intake & motec is perfect if you can stretch to it & will give you a very nice strong reliable engine & 350 hp ain't to shabby!!

Good luck in whatever way you turn & can I put my name down for first passenger ride when it's run in.....