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

[911 tweaks]

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

[Flat6pac]

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

Bruce

[911 tweaks]

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

[spuggy]

Originally Posted by 911 tweaks

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...

[x98boardwell]

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

[Jeff Alton]

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

[911 tweaks]

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

[crashmy911]

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.

[Steve@Rennsport]

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.

[dtw]

Originally Posted by Steve@Rennsport

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.

[Aurel]

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.

[911 tweaks]

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

[Steve@Rennsport]

Originally Posted by 911 tweaks

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.

[911 tweaks]

thanks Steve!
Bob

[T77911S]

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.

[Jeff Alton]

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

[Racerbvd]

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

[Jeff Alton]

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

[Racerbvd]

Originally Posted by Jeff Alton

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

[911 tweaks]

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