craig9elf

Hello.

I have recently acquired a standard piston, standard camshaft, 964 engine (L). It has aftermarket individual throttle bodies, autronic ECU and a cup car exhaust. It will be going in my 2400 pound, mid year 911.
I only really drive to the track, do a bit of very low level club racing, and then drive home, so street drive ability is not important. I do want to keep up with the higher horsepower fella's though.

Could I please tap into the knowledge here and ask what is the most aggressive camshaft profile I can put into this engine? It has standard conrods with ARP rod bolts. The standard pistons will hold back the camshafts due to clearance at some point I'm sure.

Also, what rpm should be the maximum for this engine? I'm thinking 7000 but would like to hear from those in the know.

Also #2, will I have to change the valve springs?

Thank you.

crg53

My advise would be to give Steve Weiner a call at http://rennsportsystems.com/ and discuss your engine build with him. He will be able to help you make the best choices and also supply the parts needed.

Evan Fullerton

I had Super Cup cams in my VR 993 3.6L with RSR rocker arms (no hydraulic lifters). Made just over 300whp with RSR headers and an aggressive race gas tune. Revlimiter was at 6800. In the ~2500lb 993 RSR clone it felt pretty stout but for my taste the HP peak was too close to the rev limiter to be fun. You always felt like you should hold a gear a little longer and then it would smash into the limiter. They also made the car idle like a big cam V8 which may or may not be a good thing depending on your perspective. With your ITBs, idle quality should be much better. A more reasonable flywheel weight should help smoothing things out as well but I was running flywheel and clutch out of a 997 Cup which is a 5.5" triple plate.

A friend has Super C2 grinds in his ~2650lb 964 with the rev limiter set at 7200. That car feels about perfect to my taste as far as peak power vs. redline and gearing. With ITBs though that really opens up your choice of cam since you don't have to worry so much about lobe separation and the resulting intake reversion so much.

Depending on what trans and gearing you are going to run with it, Super Cups is as big as I would go without really considering a close ratio gearbox and/or going into the bottom end to allow a higher redline.

Your results may vary and asking the experts is always helpful.

JV911

You'll need springs and retainers but even then 7000 is optimistic on standard internals.

Speak to TD Automotive or promotive in Brissy, or Autohaus down here.

porsche mania

I went for a cup spec cam shaft which has a 2mm lift at tdc which I'm sure is as far as you can go with standard pistons. The cup cams really want a higher than standard rev limit as its still pulling hard when it hits the limiter. The pockets on the piston tops are what will limit you on your choice of camshaft. You won't be able to run an aggressive enough cam to make much use of a higher rev limit that your itb's need to make the best use of them. As others have said you should have rods and a high rev valve spring kit for anything above 7k rpm. Not sure if standard pistons have enough crown to machine the pockets deeper but if you can then you can fit a much more aggressive cam and build a 8k rpm 350bhp monster. Then you'll be looking at close ratio boxes......

NineMeister

Standard rods and pistons with good ITB cams are mutually exclusive, just can't be done effectively due to lack of valve clearance and the inability of the engine to run at more than 7000rpm. At best you can fit a compromise sports cam with no more than 2mm/1.5mm lift at TDC which by definition will have limited overlap, great for a stock intake but not ideal for ITBs. In my view the best option would be to refit the stock resonance flap intake with the sports cam, OR rebuild the engine, fit Carrillos and race pistons with a race cam and enjoy a 7800rpm limit with the ITBs. This is obviously not want you want to hear, sorry.

craig9elf

Thank you for your input Gentlemen.

Sounds like I can only go as large as Super Cup/ Super C2/ Cup spec/ Sports camshafts. I appreciate the common consensus is nothing more than 2mm lift at TDC.

My plan will be to just keep the standard cams for now and teach myself how to tune my first EFI engine. SMC Autronic. I like fiddling with things like this, so that will be the enjoyment for now

Further, I may slowly accumulate the parts necessary for a rebuild to really make some power....... only 250hp for now. Depends how long I can stand having sand kicked in my face

Thank you again for your help.
Craig.

NineMeister

Before you do anything else, buy and fit a set of modern Bosch injectors which will support 400hp, then re-tune the Autronic to suit those. The stock injectors are the first bottleneck to making power from the 964 so this is a relatively inexpensive way to release a few more ponies and future proof the fuel system for any future mods. Good luck with your project.

craig9elf

Thank you NineMeister.
It's little snippets of knowledge and experience like that, that I really appreciate.
Craig.

DobermanDad

What injectors would this be? Would like to do this. Thank you

DobermanDad

Never mind, found it! Bosch 803s.

crg53

How did you come up with those injectors. To support 400 HP you will need at least 367 cc/min, the 803's only flow 290 cc/min.

August West

I got the Super C2 grind on my cams...my piston crowns were machined for valve clearance and balanced to within +/- 0.05 grams. I used 993RS valves with 993 springs and retainers. Custom Steve Wong chip, 200 cell sport cat, g-pipe, drilled airbox cover, and WEVO engine mounts (black pillows).

My next upgrades will be the injectors and possibly the mid-weight flywheel that Steve Weiner produces. Beyond that, I'll be giving my car to Steve Weiner for the Motec upgrade to get closer to 350 horsepower.

The car pulls strong and sounds amazing...above 4000rpm it sounds like the voice of God!

August West

Hey Colin, you can't tease us by telling us get more modern injectors without telling us which ones! Red Devils??? Pray, do tell!

jamesjedi

Old thread I know.....what does "In my view the best option would be to refit the stock resonance flap intake with the sports cam" mean.


I am replacing my cams, this engine is similar to mine.