Well Bob, from my research on here and talking to Camgrinder I was expecting a torque/bhp boost from the 964 cams after about 4k (given my 9:8.1 cr) and carrying on until nearly 7k.

I get the top end gains but my power seems to come in even later than 4k, although as discussed there's a question mark over my cam timing.

The question I never seem to be able to get a definative answer is how MUCH of a torque/bhp loss should be experienced at < 4k compared to stock cams? I was prepared to possibly trade 'some' midrange in return for the top end gains, but certainly not 10% !

My dyno plot seems to show an excessive loss of midrange but tbh that's just an impression as I don't know what the target midrange figures for 964 cams are (although Camgrinder agrees it is excessive).

As for your points:

#1 - I wasn't expecting it to be 'dog' < 4k otherwise I wouldn't have done it. You still have to pull out of slow corners, even on track ;)

#2 - I did race springs and TI retainers as insurance against valve float at higher rpms

#3 - I stuck with oem pistons and stock cr as other 3.0 owners I know have had setup problems with increased cr on 3.0 motors on CIS.

thanks Gary for your continued input to this thread... so... am I correct to understand that you are not very pleased with how this all turned out??
If I am understanding you correctly, I wonder why 'people' claim and will post on pelican and other places that the 964 cams are a great addition to the SC engine?? I have not been able to find the recipe for how to make this cam do as claimed by so many...
If I am miss understanding you Gary, please let me know, but I would have to agree from the graphs you posted and others comments, that by solely installing 964 cams on an otherwise stk 3.0L SC engine is not worth it and will actually have more negative affects than positive ones... am I understanding you correctly here?

Maybe someone can share their recipe with how this does work, if it is in fact true!
Bob

Bob,

Yep, a little disappointed at present. The headline (top-end) figures are great and it revs very freely, but the current mid-range is decidely lacking (compared to the stock SC cams). However, I'm led to believe (after chatting to John Dougherty ie Camgrinder and my engine rebuilder) that this level of mid-range loss is NOT normal for 964 cams in a 3.0 engine.

I (and John) feel that something else must be wrong to have caused this much mid-range powerloss, hence my question about the safe cam timing range. I also wonder whether the head porting I had done was too extreme and has possibly slowed the air down and hurt the mid-range torque ?

As yet I've not seen another dyno graph for 964 cams in a 3.0 to compare mine with.

It would be good if any other 3.0 owners with 964 cams could chime in with their dyno figures and cam timings.

I reckon that my figures are not representative of would should be expected and am hopeful I can resolve whatever is causing the mid-range losses.

Bob,

My friend Kevin has 9.8 JEs, 964 Cams and SSIs on his earlier SC. His makes great power.

I have the same setup but on a later SC and I advanced my cam timing (1.5mm). Mine makes about 25hp less than his. We tested our cars on the same dyno on the same day. See results here.

I don't know why his makes so much more power. A couple of possibilities may be that he has the larger intakes and his earlier dizzy has more advance than the later SCs. I think that I can get close to his power by having my dizzy recurved and by doing some other tweaks.

Basically I am saying that you will see a wide variety of power results from those who have 964 cams. I think that the variety comes from things not directly related to the 964 cams. It seems that most people love them once everything else is in good working order.

Oh, and I ran with a few other 911s last weekend. I brought the RPMs up to just over 6K and felt like it could easily keep going. I like my lower end power too.

I plan on putting my car back on the dyno next month and will share the results. Like I said, I still have some minor adjustments to do but I am very happy with the results.

Thanks mca, much appreciated :) Anyone else?

"there is no replacement for displacement?"

Bob, that pretty much sums it up. Power is mostly a function of displacement unless you get into forced induction. The cam merely determines where the power happens on the rpm scale.

I believe the 964 cam (and variants by DC, Webcam, Elgin) is the most aggressive cam profile for single intake plenum CIS/Motronic. Remember, the 964 engine has more displacement plus higher compression pistons to alleviate low cylinder pressure due to more overlap.

The wide lobe centers at 113 degrees is what prevents reversion and keeps CIS happy. If you choose to go higher compression pistons, you will need to go twin plug which then becomes spendy.


Camgrinder has factory cam specs on his website that I'm sure you can find a profile in between SC and 964 that will work well with CIS without giving up too much low end grunt.

IMHO, the Max Moritz 98mm P&C upgrade w/964s is the next step up w/o having to go to different induction.

Bob,
The advice I received from Mr. Dougherty at Dougherty Racing Cams (DRC) was:
"Yes, the SC (cams) on a turbo work well. 1.4-1.7 is a good setting.
SC cams can support up to 450 HP at the wheels with the right turbo.
The 964 cams are a little too much for a street driven turbo. The idle can be rough, and usually requires additional fuel enrichment that the CIS cannot supply."

I think this would hold true for a normally-aspirated Porsche as well.

As long as the piston can clear the fully extended valves at the proper timing interval, you will be OK. The CIS system relies on a vacuum to make the fuel injection part work, so you have to use a cam with a lobe overlap (centerline) of 113 degrees. I think that trumps your reversion concern. Maybe not.

I agree with everything you mentioned above.

Mark

hi guys
anybody can tell me the right timing to install 964 cams on an 1979 sc engine?
Or alternatevely, how much should I retard the timing of my SC std cam to have the Carrera 3.0 configuration?
Thanks

so it was mentioned to adjust the cam timing to get a little more low range torque. Can anyone post instructions, settings etc on how to do this and to set what. I'm familiar with the basic stock cam timing, so i'm assuming that one tweaks this by using different values, or the same values, but x degrees before tdc?

This is a pretty interesting discussion. But no mention of control of mixture in the discussion. I was led to believe that a 964 cam in a 78CIS w/o an O2 sensor and computer could lead to either an over lean situation. Possible detonation?

On the basis of this I had a set of cams ground to DC13 specs. I wound up not using them, preferring a SC grind for this engine just now. I might do a swap in the future back to the DC13.

I rebuilt a 87 3.2 with a 964 grind and it works well for normal driving. This car is not a track car.

That's part of it, but not completely accurate. By using the cam profile to raise the power band, you also see a net power increase from greater scavenging effect at higher RPM....if it's tuned properly and the heads and manifolds can support the additional flow etc etc. There is additional power to be found with cams, it's just whether you can use it or not that's the isue. If you spend all your time down low, or if gear box does not allow you to keep the revs up on the track of your choice, then more cam is probably not the answer.