Anyone running 964 cams with CIS

[Daviboy]

Is there anyone running 964 cams with CIS? If so is there and discernable HP increase? Have you changed to MSD CDI box and raised the rpm limit?

[edgarcia737]

I'm going with 964 camshafts and 9.5:1 pistons. I've got two more trips planned in my 911. Then I'm dropping motor in June for upgrades. I'm told to expect around 225-230hp. I currently running early style SSI's with a Dansk Sport Muffler. I'm limiting myself to 9.5:1 pistons so I can run 91 octane fuel. My engine currently has 8.5:1 pistons.

Ed Garcia
1977 Carrera 3.0

[don gilbert]

I put them in my rebuild (thanks tooner rob) I did a lot of other mods to like comp bumped to 9.5, complete ssi exhaust, flowed heads, very tweeked k-jet system, timing and afrs set on the dyno. (217 at rear wheel and counting on a good dynoing? day) very pleased and impressed. Not sure what to expect with just cams, but I've read about 10 hp. You will like them more if you time them a little slow, you loose a few hp at the top end, but it sure does feel good.

[Daviboy]

Don,
Thanks this is good news I am in the process of sorting out what I need for my re-build. I am planning for new 95mm 9.8:1 P&C's (assuming they will be suitable for 95 octane fuel), 964 cams, port and polish heads. I already run stainless 1 1/2" headers and a 2 in 2 out exhaust. What pray did you do to you K-Jetronic to tweek it?

[don gilbert]

Davy, an adjustable control press. reg. helps to get the most out of your cis . Sure, every once in a while the atmospheric conditions are correct for factory set warm press. and car feels awesome, but most of the time 50-55 is to high for wot on a cool day. 50-55 is just a happy medium for all condition. there are some high dollar electronic one for sale, but i made my own out of a stepper motor that I control by a knob in the cockpit. I have a gage in the dash to monitor control press. and afr's. I would suggest a wide band 02 with data logging to, makes tuning very easy. 9.8 would be fine with 95 octane (lucky you).since you are getting new p/c anyway, why not go to 98mm and build a short stroke 3.2?

[Daviboy]

Don I have been considering 98mm however a forum member has a set of 95mm P&C's at a very good price and I am budget constrained right now.

[Halm]

I am running 964 cams and SSI's. Noticeable difference over pure stock SC's, but no dyno numbers.

FWIW, I have read that 964's don't add any HP, just move what is produced to a higher RPM range. Maybe so, but I really like the results.

[Brian 162]

I've had it done as well. I do have the stock CIS pistons. At the same time I added SSI heat exchangers and an early style muffler.The car was better. Big difference when the vacuum unit was replaced in the distributor.

[SP2]

I did it to an 81 3.0 SC motor with SSI's. Probably less power below 3500 RPMs, the the engine takes off. The engine sounds different too, like it is searching for more air. I was pleased with the results.

[Gunter]

+1.

[Joe Bob]

I did it after a stud replacement. Woke my 914/6 up quite nicely...

[Ed Bighi]

In my 930 this was a very effective mod. Stock intercooler, turbo, everything. Except for 964 cams. I forget the numbers, but it was substantial on it's own.

[Daviboy]

Thats it then the CIS is going back in with the 964 grind cams. I am also planning on new 95mm P&C's (unless I can get away with 98mm ala 3.2 SS?)refurbished heads with new hardware springs set for 964 profile and new conn rods. The CIS is stripped and is being cleaned and checked. I am going to have the injectors cleaned and tested as well.

[DanielDudley]

I am running euro pistons with hot cams. Much more power from 4K up, and tractable all over the rev range. I'd maybe give up a little top for more midrange, but it is actually a great combination. Do this and change your overall gearing, and you would have a rocket.

I had to change cams anyway. I here that Web Cams has an autocross grind that sounds like a hot ticket for the street, but I have never experienced it.

[Gunter]

Originally Posted by Daviboy

Thats it then the CIS is going back in with the 964 grind cams. I am also planning on new 95mm P&C's (unless I can get away with 98mm ala 3.2 SS?)refurbished heads with new hardware springs set for 964 profile and new conn rods. The CIS is stripped and is being cleaned and checked. I am going to have the injectors cleaned and tested as well.

The cost of new 95 mm P/c's should be close to getting new 98 mm P/c's.

Either way, the 964-profile gives just a little more lift and stock springs can be used.
Connecting rods can be re-used; just the brass bushings are replaced.
Use ARP bolts on the rods.

Injectors cleaned? You can soak the injectors fully submerged in injector cleaner for a day and then blow out with air.

CIS stripped and cleaned?? If the fuel distributor didn't give any trouble, I'd leave it alone. Just replace the rubber sleeves on the intake runners and new gaskets on the ports.

If it hasn't been done for a long time, consider servicing the ignition distributor:

Distributor service (Clean and lube) real easy without removing the pinion gear! - Pelican Parts Technical BBS

[Daviboy]

Gunter,
I cleaned and serviced my distributor previously as per your tips. What I mean by the CIS stripped and cleaned is that I have removed all components from the airbox and am externally cleaning them as all components are working fine. In need new conn rods as #2 is bent after the valve drop story unless you have a stock rod you dont need. Am going to go with ARP rod bolts. The reason I am leaning toward 95mm is that a forum member has a set of P&C's for a very good price right now. Thanks for the injector cleaning advice will get some cleaner tomorrow!

[RWebb]

you can also send or take your injectors to a prof. cleaning shop for very few $$

[rgoodrich]

I have an 81 3.0, using Mahle Euro pistons, 964 cams (Dougherty re-grind) with Titanium retainers, and a PMS flywheel. Exhaust is Fabspeed headers and 2 out. CIS has been fully cleaned, with new regulator and fuel pump. It runs like a dream, and screams from 3200 up. Hasn't used a drop of oil in 1400 miles.
Very happy with overall setup. I don't want to lose an reliability, so this is all the engine mods I need.

[Gunter]

Daviboy,
A replacement rod has to have the same weight as the others!
The shop should know what to do, like replacing the bushings and make the rods weigh the same.
Waite until you have all rods, then take them to the shop along with a wrist-pin.

If the case is split, consider doing some mild boat-tailing.
Do a search on this.

Once all is back together, you can test the cleaned injectors by connecting them to the lines and placing them in 6 equal-size glass jars. Let the pump run for a few seconds: Ignition ON, lift the airsensor plate. The jars should show equal amounts of fuel. You can also test the spray pattern that way.

[911st]

Can anyone document that C2's actually alow an SC motor to make anymore peak foot lbs of TQ than SC cams by themselves? Or do they just move the TQ to a higher rpm which by definition would make more HP?

The stock SC cams are a great cam and about as good as it gets for a low compression 3.0/3.2 street motor.

If one wants more HP, I suspect that all one needs to do with the stock SC cams is to set there timing to what Porsche did at first with the early euro 1977 Carrera 3.0. This will move the TQ production to a higher rpm level and more HP will be made.

The C2 cams close the intake valve later at the start of the compression stroke which makes for a lower effective compression rate. I think it is like lowering the 'effective' compression ratio by about a half a point. This is at the expense of low rpm TQ.


There is probably more to be gained from exhaust, proper AFR, and ideal ignition timing. Also, for the later small port SC's I would open the intake up to 36mm if possible. 39mm is way to big for the HP level the SC operates but can be in improvement at higher rpm's.

If one is going to go with C2 cams they might want to look at the valve springs, higher seat pressure, and or lighter spring ratainers as they have more lift and even steeper ramps that need to be accommodated.

Me, I would not spend the money on C2's. They are a better fit with motor that can make its own low end with higher compression, larger capacaty, and the lower pumping losses with the later ignition sthat comes with twin plugs.

Stock SC cams with a full race exhaust, euro pistons, advanced cam timing, and custom EFI intake have made as much as 270hp, thus they are a pretty good cam depending on one's goals.

Not an expert, JMO.