964 cam vs. SC cam on 3.0L w/ CIS & SSI
 

I am sure a few Pelicans are running the 964 cams on a stk 3.0L engine w/ CIS & SSI's, and I was wondering what are the noticable differences in engine performance ?

Also, if you did this cam 'upgrade', did you also and/or as a result, do any other upgrades to the engine?

I know this question can be interpreted a few ways, but I am considering wether or not to install the 964 cams, that are sitting on the shelf collecting dust, in a stk 3.0 w/ CIS & SSI's engine and wondering if worth it and if I do it, do I need to possibly use different/better valve springs,... ect.?

Thanks guys!
Bob

964, if you have then, use them. Its got to be better than stock and theyre no good on the shelf.

Bruce

I am led to believe that they are better also Bruce.

Anyone have any specific comments as to what is better? ie. more torque on low end possibly or revs quicker or tighter torque band vs. SC or if you run the 964 cams you also must do so and so part swap out... That is the kind of info I am looking for here.

Thanks in advance to those that can share their own set up ~ experiences and opinions.
Bob

According to John (camgrinder) Dougherty, they make slightly more top-end HP, at the expense of low/mid-range torque. So they'd likely work well for an N/A car for track use with a close ratio box, or lighter than stock car.

I don't know anything about possible clearance issues with CIS pistons - especially if you have the higher compression SC pistons. I'd get an opinion from someone who knows about that before fitting 'em, if I were you...

Correct
 

964's do make more top end horse power. I just took them out of my 930 and went with SC grind so that I would have more off boost torque.

Unless you are tracking the car and in the high RPM's often then I would go with SC all the time.

Best of luck,

Bryan

I have built two 3.0's with 964 cams both with stock exhaust. The cam makes for a motor with a very similar power band to the stock cam. But, when it comes on the cam, it comes on harder and makes more power.

I did not dyno either motor, and the customer did not care to, but it makes a nice strong 3.0 with good torque. I did not notice any lack or decrease in the bottom end power.

A lot of 3.0's have pitted cam lobes anyways, which requires a cam grind, so going to the 964 profile (which does not cost any more) becomes a no brainer....

A 3.0 with 964 cams makes a nice motor.

Cheers

Thank you everyone for your input here!

Jeff: So you don't think any performance i.e. torque,... will be lost on the bottom end if I install the 964 cams and the top end will have a noticable improvement when it comes on cam which is around 4-4500rpm??
Also, this particular engine is an 81' w/ sm port heads and stk springs as far as I can see: will these be ok or should different parts be used here ?? (for the record... the car is destined for street use 95% of the time where 0-100mph is all that is important...it will see a few d/e's for kicks and to see how she runs but no competing or time trials type of use)

Thanks, Bob

964 cams
 

I've got this upgrade on my car. I would say it raises the power band. If your puttering around on the street might as well keep the sc grind in there. If you are opening it up and have them do it. But put the better valve springs in there . You will be revving the car more with them in. My car is a 78 with the lower compression so you really notice the power loss when just driving around in traffic. You will go nuts with it like this if in alot of traffic. Mine is a slug when off the cam. Below 4000rpms it is a major dog. On track you can hold gears longer and it pulls alittle longer. Auto cross would be better with sc grind.

Hi Bob,

Just my 2 cents here,...:)

If this is a street car, I would not likely use 964 cams due to the reduction of bottom-end torque unless I had close-ratio gears. These exacerbate the soft throttle response that CIS systems typically have below 4K.

What you can do is time your SC cams to somewhere between SC and Carrera 3.0 for more upper end pulling power without compromising low end as much. Bear in mind that your small-port 3.0 was optimized for low & mid-range power, compared to the early SC's and Carrera 3.0's with larger ports.

I agree, and Herr Weiner's input is dead-on w/what my research unearthed when I was looking into this for my "Ultimate 2.7" build. It goes against the conventional/standard advice seen on the board, but it is worth considering IMHO.

Bob, dig up that thread and you'll see some graphs that Jamie put up plotting the stock 2.7 CIS cam against the SC cam. Same idea as 3.0 vs. 964; the newer cam gained a bit of top-end whlie giving up midrange grunt. My engine build was for a car that is on the street 99% of the time, so that didn't make any sense to me - I think your build is also a street car yes?

I talked with another builder who is on and off the board from time to time, and he recommended a strategy similar to Steve above, just giving the cams more static advance. I forget the specific numbers, but I did advance my 2.7 cams as much as I could get away with.

Not sure if it is the compression bump or the cam trick, but my 2.7 screams. Probably a little of both. I actually want to race the car against my Carrera, I am not sure the 2.7 would give up any ground to the 3.2. This, based on my impressions of driving each car back to back this weekend.

The choice of cams must be made in relation with the compression ratio of your motor. With CIS induction, 964 is the most agressive cam that can be used. Typically, 964 cams work better with a compression ratio higher than 9.5:1, while DC15 or Webcams2021 or Elgin E330 would be a better choice for engines with 8.5:1 CR. Those cams, intermediates between SC and 964, are also great for low-end torque and street driveability.

thanks steve, dave & aurel for your info...

If I may ask of Sir Steve W... how far do you recommend I can advance the stock SC cams and not have detonation a/o piston contact issues or some other problems ??

#2. Would this advancing "require" the engine to now run 93 octane, though it would probably use 93 anyway ?? (single plug engine here)

#3. And last, does the dizzy need any "tweaking" to run the cams at this advanced setting or anything else while in there ?? (I wince to ask this last question... ;-)

Thank you!
Bob

Hi Bob,

For clarification,..advancing the cam timing builds more low-end torque at the expense of upper-end pulling power. Retarding cam timing makes more top-end power at the expense of low-end torque.

The confusion comes from tweaking ignition timing which has opposite effects (more timing, more low-end torque). :) :)

If you use the factory cam timing values (various SC and Carrera 3.0), you will not experience detonation problems or piston-to-valve contact. For the record, I strongly recommend the use of premium fuel in these cars.

Ignition timing is adjusted after the cams are set and everything is all back together and running. Depending on local octane availability, I would use 30-33 degrees total at 6K RPM.

thanks Steve!
Bob

i just bought an 82 3.0. i am planning a valve job ASAP. if the money is available i want to change the cams. i like the idea of the low end power of this engine and was wanting to emphasize this, or at least not take away from it. what i was considering was either the 964 or the 20/21 cam with some advance. from what i have read, the 20/21 seems to have a more broad band than the 964. i was also thinking of finding a ROW CIS with the big runners and having the edge of the ports opened up to match the runners but leaving the overall port size stock, but not sure if this would be worth the money.


when i bought my 77s, you could not floor it or run it past about 3500 RPM with out spark knock. i found that retarding my ignition timing (IT) about 15 deg allowed me to run it up to about 5k. i had the motor out for something else and decided to check the cam timing (CT). it was around 15 deg advanced. i set it back to spec, no i can drive it hard, although i have a slight miss at 4500 and it just does seem to want to pull to 6.

My experience has been different than that posted by others. In the motors I built I did not feel any decrease in bottom end performance. YMMV......

The 964 cam is still a pretty mild cam...
Cheers

When we rebuilt the engine in my 83 cab, I went with the 964 cams, SSIs, euro FI & a few other bit, this has great low-end torque, one of the first times I took it out, a light was getting ready to change & I punched it, lit up those 9X16s like never before:eek:

byon, are you heading to the 24? shoot me a pm or email if you are going, I will be there..........

Not sure yet, depends on how I'm feeling, may just go for Fri. did you see something on my list that I can trade you for a set of wheels or two:D

Hey Byron... an you elaborate on what is the difference in the euro fi and the "other bits" that you ran with? did you ever dyno it or seat of the pants dyno as you said while leaving the street light...
Thanks,
Bob

Never put that one on the dyno, but compared it to my 78SC & Carrera(both still mostly stock, it is much quicker, and both SC run 245s on 9X16 Fuchs:D The Euro system is pretty much the same as 78-79 and a little bit of head work, SSIs flow into a B&B muffler. Makes for a very fun cab:cool:

Hi Bob,

Greetings from down under.

I did this upgrade when I did a rebuild of my 204HP 83 SC. I had pitted cams so I decided to go with the change. Bearing in mind that I put in new rings, and had the heads freshened up also, so obviously the engine response is better anyhow, but I think the low to mid range is quite a bit better than before. The engine pull pretty strong from as low as 1800 rpm, when 3000 -4000 happens there is strong acceleration. My engine seems to run out of puff after say 5500 but I usually don't rev it that hard anyway. The SSIs would probably help up around 5000 for you.

Interestingly I found by experimentation that the car is happier running with the ignition timing advanced slightly. If I set the advance at 4000 to the mark on the fan belt pulley the engine at idle indicated 0 degrees advance ie. TDC. I advanced the mark at idle approx. 1/4" on gthe pulley. Straight away the engine pulled like a train. no pinging issues

By the way I run 98 octane as recommended by porsche.

From what I read about the STD v. 964 cams the concensus was that the change is minimal in but it is the max recommended due to issues with the CIS.

hope this helps.

Greg

I thought the 964 cam was the thing to do when you did the MAx Mortiz mod, 3.2 SS.

That is what I am running. I don't have any prebuild dyno data but the change is quite dramatic. There definately is an "on cam" sense with this combo at about 4000-4500 rpm. The dyno shows a very smooth torque increase to that point. Because of that "on cam" feeling, you do feel as if you are lacking low end torque but it is an unfair comparison to the stock setup without a pre and post dyno comparison.

Hate too tell you this but with 964 cams you will make power till 7000 rpms. Not in the low rpms.

Interesting timing (no pun intended ;)) I was just talking to my engine rebuilder about this today!

When I had my euro 3.0 SC '82 engine rebuilt I switched to 964 cams. CR was left standard at 9.8:1 After it was run it had a different character than before. Although it now revs to 6800rpm

http://i142.photobucket.com/albums/r...ril_7k_rev.jpg

and makes 232.1 bhp it lacks midrange torque compared to the 3.0 SC cams. This 'seat of the pants' 'butt dyno' is backed up by the figures from the real dyno runs.

Here is the 'before' dyno plot:

http://i142.photobucket.com/albums/r...7DynoPlot1.jpg

and now the 'after' one:

http://i142.photobucket.com/albums/r...8DynoPlot2.jpg

To save the bother of trying to compare them (they annoyingly have slightly different scales !) I've summarised the differences below.

SC cams: 964 cams: SC cams: 964 cams:
---------- ----------- ---------- -----------
RPM: BHP: BHP: Torque: Torque:
----- ----- ----- --------- --------

2500: 85 81 (-4) 177 164 (-13)
3000: 105 98 (-7) 185 172 (-13)
3500: 128 120 (-8) 191 179 (-12)
4000: 160 145 (-15!) 209 190 (-19!)
4500: 180 171 (-9) 210 199 (-11)
5000: 200 191 (-9) 208 200 (-8)
5500: 210 216 (+6) 200 202 (+2)
6000: 216.6 224 (+7.4) 190 196 (+6)
6300: 213 230 (+17) 178 190 (+12)
6500: ---- 232.1 186
6700: ---- 232 182

Both runs were done on the same dyno (moved from one premisis to another). It's well respected here in the UK (used by motorsport teams to test cars for racing series) and has proven to give repeatable results.

I've lost almost 10% power and torque in the midrange. I've spoken to John Dougherty (Camgrinder) about this (he didn't actually supply the 964 cams in the end as he was out of stock, but is just a very helpful, knowledgable guy) and he reckons this extent of torque/hp drop is not normal for 964 cams in a 3.0 204bhp SC engine.

We're going to check the cam timing. Was supposedly timed at stock 964 figures, ie 1.26 and will maybe experiment with advancing it to try and regain some of the midrange torque. John said he'd recommended values as high as 1.8 for low compression (read 8.5:1) motors to regain midrange grunt.

So, does anyone know what the safe (ie avoiding valve/piston clearance issues) range of cam timings is for 964 cams in a 3.0 SC engine. Porsche specs only give the single 1.26 figure for 964 cams, not a range of values like they do for the SC. I don't want to move outside of the safe range!

As an aside, I also had the heads mildly ported during the rebuild and was wondering if that may have had a negative affect on the midrange performance ?

Cheers - Gary

thanks Gary for your post... I too want to know thew answers to your questions to see the differences.
Bob

I think I read some stuff here on the forum, that some guys has set the timing at 1,6+.
So I guess you'll be fine, but youl'll have to check the piston/valve clearance anyway. -But won't you loose some of the top end power?

Will probably lose some top end, but having done 10 trackdays last year, including the Nurburgring and having her lug out of the low speed corners I'll willingly trade some top end to regain the mid-range torque. It's that whole 'area under the curve' thing that I'm really being to appreciate now. 'It's torque that wins races' isn't that the saying ;) ?

I put 964 cams in my Euro 81 SC and it is only a street car. There was a noticeable difference in power. I also put in SSI's at the same time so I am not sure how much each contributed to the power.
But I will say that every morning I have a very, very steep hill to drive up to get my coffee. In low RPM's the lack of power is very noticeable. You need to be at least 3000-3500 to be in a comfortable power range.
But on regular streets I love to drive this car. It is my daily driver.

Noone got any values for timing 964 cams in a 3.0 engine then? :confused:

Btw, here's a (rough) plot of the before and after dyno plots overlayed on the same graph showing the mid-range losses:

http://i142.photobucket.com/albums/r...8/DSCF1630.jpg

1.26mm

Currently set to that SP2, but as you can see from the graph I reckon there may be more midrange to be had by advancing it from 1.26?

That spec is from john dougherty. I'll look at my dyno reading tonight.

Thanks, I'd be interested to see a post of your dyno chart SP2 :)

WOw 6800. My car feels like it will pull till it explodes. IF you fall below 4000rpms there is no power at all. It makes it very difficult to stay in the power band. I'm a novice driver and I'm sure that is some of the reason. An experianced racer drove my car and he said he had to be in a lower gear then his stock car to have any type of power. He liked what I had done but said it would be hard for me to learn to drive as a beginer. My car feels like it is still making power at 7300rpms.

What have you had done to your car crashmy911 ?

I would like to hear the engine setup of crashmy911 as well.

I have the same situation as the thread creator had. New 964 cams sitting on the shelf for 7 years and now my 81 US spec engine is out and on the engine stand and I want to put them in.

I spoke with Mayo in Dallas today about the task. They are in the same class as Steve Weiner. Steve is a god from my viewpoint after he convinced me to buy the MSD 6AL ignition six years ago over the phone. Anyone need a couple of dead Permatunes?

Tom at Mayo noted that the springs should be upgraded to somewhat stiffer than stock as the ramp on the 964 cam is steeper than the SC and can provide an opportunity for valve float if you spin your engine above 7k. He also said that stock and mild performance 911/930's that had been run routinely at high rpm in their life may have small, invisible to the eye, stress cracks in the spring retainers. He suggested for insurance that you replace these as well.

Don at Engine Builder Supply did not see a big problem with using new original springs but said that you optimally should set the spring height to 964 specs. Mayo did not stress the 964 spring height adjustment and said that using the original SC shims was fine - given getting stiffer springs.

So new springs are recommended - original (and cheaper) style if you feel lucky. I believe Mayo said there was 60 pounds pressure on the stock springs (at "rest") and 90lbs on the springs he buys from Engine Builders Supply. Under full compression I believe I heard the pressure was 180 (original) vs 250 (upgrade) pounds.

Mayo also stressed the usual CIS false air checks with the engine out. Stressing the injector o-rings and the injector sleeve that is in the intake runner which holds the injector and it's o-ring. There is an o-ring on that as well that you cant see unless you remove it.

Race springs and TI retainers on my motor Bob (a bit of insurance against the occasional high rev ;))

so guys, do we have any general concensous about using the 964 cams in an other wise stock 3.0L and is it worth the effort??
The points I read ~ infer from the posters are:
#1. at <4k RPM the engine will be a dog... above 4k to beyond stk redline of ~6200 it will pull significantly harder vs. stk cam. I interpret this as a trade off & not a good one for street driving, especially, no matter how aggressive one drives as it would require to run the engine at 3500 + rpm MINIMUM to avoid the sluggish acceleration. On the track a different story as you are running close to or at full out to perform best at race.
#2. If the above is understood and accepted, one should do more than just installing the cams and thinking they are all done with it. Higher spring rate valve springs, cups, retainers, shimming possibly are all recommended as the 964 cam will want to be used by the driver = driving & enjoying 4k-7k? rpm travels and you Do Not want valve float on these engines to avoid valve/piston collisions.
#3. my overall conclusion on this subject, AND PLEASE INFORM ME IF I AM WRONG, is that like ALL modifications to the engine, they need to be considered in the 'big picture' of what one is trying to achieve here and how best to accomplish such remembering that the engine is a 'complete system' and needs to be thought of as such. So, if I were to install 964 cams I would think it best to also swap out the OE pistons to allow for a more aggressive camshaft. A cam shaft that would still be compatable running CIS injection which is the REAL LIMITING FACTOR HERE due to reversion occuring when too aggressive os a cam is used.

So. what is the most aggressive pistion and camshaft we can use, retaining the stk cylinders & stk CIS injection, AND, THE ALL IMPORTANT QUESTION, "will this piston/camshaft combo not have reversion issues, increase performance vs. stk 3.0 engine and not have the <3500 rpm doggie performance?? (my guess here is IF this will work as I am sure someone has done some combo here that the parts cost was $1-2k + tune~set up time all for 10~20 hp which to me is not worth it... might this be the adage, "there is no replacement for displacement?")

Thanks all for keeping this thread alive and lets see if there is a REAL benefit option here via swapping in & out parts with what costs & +/- performance results.
Bob