964 cam to stock 1980 911sc

[$yncro]

Hi there, I’m new to the forum..been doing a lot of research regarding 964 cam and finding a lot of mix reviews. Currently rebuilding my project 1980 911 sc engine and found a slight pitting on one of the cam lobe #4 cylinder. Decided to get it regrind to 964.
Now I’m contemplating on maybe stay with stock SC profile. Or should I just go for the 964? Car is basically a street car. TIA for the input.

Btw, rebuilding engine due to its a barn find, blown airbox, found 2 clogged injectors and 5 broken lower head studs.

[$yncro]

Seems like there’s not enough pros on the 964 cam for street daily driven car
Don’t want to mess around with rockers, timing and such so I decided to go with
The sc stock profile. It’s my first Porsche, just want a strong reliable engine.
Too bad they didn’t have any ECU map piggyback/ alpha N like what I had on my
88 M3. The power band is bang on as soon as you step on the pedal.

['76 911S 3.0]

964 profile will fatten up the torque curve, great addition to a 3.0L for a street driven engine.

[$yncro]

I have the late heads with smaller ports.
I’m going with the backdated SSI exhaust,
Seems like that’s the nice safe upgrade since
I need one.
Thanks

[Trackrash]

Yeah, by '88 Porsche had chips doing the tuning as well.

Who is doing your cam? You should call John Dougherty, AKA camgrinder, and ask his opinion. There may be other options for cams to consider since you are backdating the exhaust.

Also, looking ahead, since you are rebuilding anyway, pistons and different intake can REALLY wake up one of these motors. The limiting factor for your cam is CIS and stock pistons.

BTW, The right sport muffler can be worth some extra HP as well.

[trond]

i would consider to not replace that cam. if you want to stick with stock profile that is and especially if the matching rocker pad looks good ? I went back to stock profile myself based on my own taste and use of my car and will stick to that

[$yncro]

Originally Posted by trond

i would consider to not replace that cam. if you want to stick with stock profile that is and especially if the matching rocker pad looks good ? I went back to stock profile myself based on my own taste and use of my car and will stick to that

Thanks.. yup after some digging in the net regarding pros and cons of
Changing cams, not just 964 in particular..seems like for my purpose usage
Of the car is to go stock for now. Meanwhile I took off all the ac components.
Looks like shaving off a little weight is a way to gain hp.
Cheers.

[AndrewCologne]

I have the late heads with smaller ports.
I’m going with the backdated SSI exhaust,
Seems like that’s the nice safe upgrade since
I need one.
Thanks

You'll suffer from mid range torque loss. The benefit of 964 cams is rising the power band on high revs from 5500 Rpm and above. And in case of engines with small ports – here for a sufficient airflow the diameters are too small for a benefit of cams with power present on high revs.

See in this thread further below, its in german, but an online translator will make it at least a bit clear for you:
http://www.elfertreff.de/showthread.php?t=26670

Especially this one where you can see more or less whats the approx. difference between SC and 964 cams in a 3.0 CIS engine.



The whole torque will be moved forward to higher rev areas.

[spuggy]

Originally Posted by $yncro

Too bad they didn’t have any ECU map piggyback/ alpha N like what I had on my 88 M3.

There's at least 2 piggyback or replacement ECU systems using the factory harness for the 3.2 with Motronic. If you'd bought an EFI car, that would've made it easier...

Plenty have added injector blocks/fuel rails, sensors and a toothed crank pulley to convert CIS to EFI. But no piggyback, as there's nothing to piggyback onto.

I do seem to remember conventional wisdom being that SC/3.2 cams are about as far as you can go with CIS - too much reversion for good manners with anything wilder, you'd need carbs or EFI.

For a street car, I'd trade low/mid range pickup from the lower torque of SC cams against a few extra ponies at red-line. You'll get the advantage of one a lot more than the other.