964 3.6 cam upgrades

[jpnovak]

What is the current thought on a cam upgrade for a 964 based 3.6?

Considering a 3.6 swap into an 87 G50 Carrera. The target application would favor high-rpm character at the expense of low-rpm torque. I would assume that we can get 6800 rpm out of the stock bottom end.

Induction would be plastic (Nylon) 964 intake manifold and the possibility of ITBs. The car will have a stand-alone engine management system. Emissions are not a concern.

The factory torque curves show HP drop significantly after 6k rpm. I am just thinking a cam choice would fill in the power for that last 800-1000 rpm band.

I know there have been some builds with 993SS type grind. Any dyno curves/output graphs for these cams? Are there any other grind options available?

[Nux]

I've built an otherwise stock 964 engine with 993SS cam. Mild upgrade 248 vs 246 at 1mm and 0.02" higher lift.

Noticeable change in top end but still fades a little at redline. Minimal bottom end loss. Expect 10 maybe 15 isch hp gain.

I guess it corresponds to the well known 964 cam in a 3.0. Personally, I would choose a little hotter cam for your application. DC21 with good exhaust? But I'm no expert at all.

[jpnovak]

Thanks I started with the thought of a 993SS. Then quickly started thinking of more. Thank you for the real world notes on gains.

John D. recommended the DC24. My calcs show it should push the peak HP right up close to 7k.

Just to be clear. I am not interested in peak numbers. Just in shifting the torque curve and filling in the top end of the rpm spectrum.

[Tippy]

I remember these numbers on a 3.2-3.4 (not exact, just for reference):

1. Stock 3.2 cams - 6100 peak
2. 964 - 6300
3. 993SS - 64-6500
4. GT2 Evo - 6700

Point is, wouldn't you need bigger than GT2 Evo's for a 3.6 to get a 7k peak? The valvetrain starts to get real critical with cams that large!

[175K911]

I’m running Dougherty’s 993SS in my warmed over 3.6, car is 98% track. I considered John’s DC21 profile which is a little hotter but with 112 degree lobe separation which would have shifted the power curve up slightly but at the sacrifice of a bit of midrange torque and idle. But for you that might be a good choice, if I hadn’t already waited 3 months for my cams, I’d have switched to the DC21.
Talk to John, ask his advice. Wealth of knowledge.
Oh and don’t forget better valve springs too.

[KTL]

Take a look at 911Chips dyno page. You'll see that despite various cams and exhaust in the 964 3.6 engines, all the hp peaks are at 6300 and the flat torque peaks all seem to drop off at around 5500. This is similar to the 3.2 engine dyno plots on the page. That tells me the induction is the controlling factor?

[Steve@Rennsport]

Jamie.

The biggest cam you can use with the stock, single-throttle intake are the 993SS ones due to reversion issues. I would be careful about using ones with less than 114 deg LC's due to idle & drivability below 2K, especially with that light flywheel used in the conversions.

Beyond that, you need ITB's and of course different pistons with sufficient valve clearance.

[jpnovak]

Thanks everyone.

A few more conversations have filled in some more details.

Steve you are right about reversion and the AFM flutter at low rpm. The current plan is DC24-114. The widened lobe center should help with reversion as well as piston clearance on the exhaust side.

However, Kevin you make a great point about intake flow limitations. I was under the impression that this would flow enough to support higher HP like a 3.8RS. I would think the exhaust would be more restrictive than the intake. The planned exhaust is 993 HEs into a 991 muffler.

Eventually the car will get ITBs but the budget will need to recover after the initial installation. Though I am not sure if there will be enough extra output to justify the installation. Will see how easily it is to adjust to the extra power before sliding further down the slippery slope.

[Bill Verburg]

Originally Posted by jpnovak

What is the current thought on a cam upgrade for a 964 based 3.6?

Considering a 3.6 swap into an 87 G50 Carrera. The target application would favor high-rpm character at the expense of low-rpm torque. I would assume that we can get 6800 rpm out of the stock bottom end.

Induction would be plastic (Nylon) 964 intake manifold and the possibility of ITBs. The car will have a stand-alone engine management system. Emissions are not a concern.

The factory torque curves show HP drop significantly after 6k rpm. I am just thinking a cam choice would fill in the power for that last 800-1000 rpm band.

I know there have been some builds with 993SS type grind. Any dyno curves/output graphs for these cams? Are there any other grind options available?

W/ a stock bottom end, Intake and engine management 993SS are the way to go

[Nux]

Originally Posted by jpnovak

Thanks everyone.

A few more conversations have filled in some more details.

Steve you are right about reversion and the AFM flutter at low rpm. The current plan is DC24-114. The widened lobe center should help with reversion as well as piston clearance on the exhaust side.

However, Kevin you make a great point about intake flow limitations. I was under the impression that this would flow enough to support higher HP like a 3.8RS. I would think the exhaust would be more restrictive than the intake. The planned exhaust is 993 HEs into a 991 muffler.

Eventually the car will get ITBs but the budget will need to recover after the initial installation. Though I am not sure if there will be enough extra output to justify the installation. Will see how easily it is to adjust to the extra power before sliding further down the slippery slope.

Did you decide on that DC24-114 cam? I just bought another 3.6 engine and I'm starting to plan some small upgrades. Is the DC24 compatible with stock pistons and stock plastic intake?

[JohnJL]

Funny, I have DC24 cams with 108 separation on a 3.0, aluminum carrera intake with ported heads, and I have has a *unt of a time getting it to idle smoothly. John recommended the DC24 and the lobe separation for this motor. I know JP tried to help a while back...Idles now but minimum 1000 rpm. Every stoplight I pull up to its already revving, so everyone wants to race (which sometimes I do ;-)