964 Intake +Cam Choices

[jamesjedi]

Hi,

I have read Waynes book about the 3.0 L engine rebuild. Great book. It says that removal of the CIS can free up the engine and allow for other modifaications that can increase perfomance.


If the CIS is replaced with a 3.2, or 964 intake, and mated with adapters that allow it to work with the 3.0 L cylinder head, can the "Early S" cam be used?

I am looking to compare these two builds. I am trying to see if it is worth spending the money.

- early S cams
- 10:1 JE's
- 964 intake and 964 injection plumbing using the adapters for mating the injectors.
- twin plug, Euro heads

How much gain is this over the use of;

- retaining the CIS (mostly Euro)
- 964 cams
- 9.5:1 JE's
- Euro heads

Input would be appreciated. Thanks.

[Walt Fricke]

I'm not sure the 3.2 intake is a good candidate here, unless you have one sitting around and that saves $. One hears that it does not do all that good a job distributing the air from the single throttle body.

Don't know about the 964 intake, but look up the Spec 911 rules (mostly a West Coast racing class, but also adopted in the PCA Club Racing rules), which make a provision for using this as one option. The notion there is that the various configurations allowed, plus some weight adjustment, creates equal performance.

The late Euro SCs (big intake ports, big runners, 9.8/1 CR, and a good exhaust) tend to outrun the 3.2s in racing despite the displacement and EFI advantage the 3.2 has. Though the 3.2s have the same cam as the SCs, so aren't taking advantage of the EFI in that respect.

Twin plug is always nice, and with it you should be able to run 10.5/1 CR and certainly the S cams, if not something even hotter.

A lot depends on the use, and if for racing, what rules allow.

[jamesjedi]

Thanks for the reply.

What kind of power would be from the first motor. That said, I am not sure that the early S cam would even work with the 964 plenum? This can be confusing.


Engine will be street driven, hopefully raced soon (does not have to be a high reving engine, as "racing" is not the focus), lots of autocross. I want a snappy engine with area under the curve. Peek power is not the focus.

[jamesjedi]

Talked with Jeff at Rothsport.

I hope I do not misquote him; Cam is limited to 964 or similar. 964 Plenum can be used without ITB's, when adapters are used, however, drivability is sacrificed. It does not start, idle as well as ITB's. ITB provide instant throttle response.

Performance is increased considerably over the CIS with the use of common plenum intake.

ITB' are the way to go. They are also expensive. Very helpful and informative. Cant say enough about him taking the time explain this kind of set up. Thanks Jeff!

[Trackrash]

There are "hotter" cams that will work with the stock injection system. A friend of mine uses the Web 20/21 cams in his SC with 98 P & Cs and the CIS system. Sounds and runs great, even if it idles a little rough.
Depending where you live smog certification could be an issue with any non stock setup.
Here is a sc motor with a Carrera intake. My $6K Porsche 911

[jamesjedi]

Any idea which 964 intake to use. It looks like the plastic one is lighter, and designed a little different with a single butterfly inlet. Is there a more desirable year for this conversion?

[kandhmfg]

Having run several different 3.0L and 3.2L combos over the years, stock early big port and late small port 3.0, stock 3.2 (with SW chip and bypass), 3.2 S/S using CIS and 20/21 cams, 3.2L S/S 9.5:1 JE's single plug with mod S-cams and 46mm carbs, my analysis is this:

All of these will yield a 200 - 250 fwhp power range and can be relatively inexpensive/easy to build/maintain. Stock 3.0 CIS/3.2L intake engines have good torque on the bottom, carbed and cammed are freer on the top. If you have a 3.0L to start, easiest and biggest bang for the buck is going with 98mm P/C, the 20/21 grind cam. Lots of low end torque and good driveability, lower redline. If you want to spend a little more, the ITBs or carbs and higher lift cams (S cams and above just add another level to the rev range and peak hp, not to mention the intake sounds are intoxicating.) Just depends on budget. Your 3.0L is an easy carb conversion. 40s or 46s can be made to work depending on cam/compression. You can run single plug reliably even racing if kept under 9.5:1. The Euro or 78/79 distributor is fine without recurving. I use a stock Euro distributor in mine works fine advance wise.

All these engine combos are going to be great, but the best way to take advantage of any of these is to lighten the car to 2300 lbs +/- (as light as you can get it), put shorter gears in the gearbox 3, 4, 5 to take advantage of the powerband from 4000-6.5-7,000, do a tried and true standard 23/31 torsion bar setup with adj sway bars, monoballs, and add R-compounds and negative camber. Go drive. Out of the box you will grin from ear to ear.

Talking to Jeff at a Portland event one time, I think the Spec 911 guys running 3.0s using the plastic 964 intakes are getting about 250 fwhp with ITB's and efi. But, I think that air cleaner sticking out the back of the engine grill is kinda ugly and high dollar. I think the Carreras get about the same with their allowed mods, but I believe the Carreras have to run heavier than the SC that is why the SC gets the advantage. Similar hp but lighter weight.

Also many of these 3.0/3.2L engine combos tweaked a little with exhaust can regularly run with most of the typical D/E pack and even in midrange race groups. They can even run with the stock 3.6L transplant into earlier 911 crowd. A couple of us in AZ doing it in NASA race groups.

I am sure you will have fun whatever direction you go. Key is to keep er on the track for maximum enjoyment not on the trailer or garage. They are fun to work on, but in my experience you reach a point you just want to drive the damn thing, not work on it.

[jamesjedi]

Thanks for the insight. 250 hp would be amazing.

I can see the fun in 3.2 short stroke. Looks like a great build.

I do like the idea of the 964 intake, but I did not know that the air filter stuck out the back.

[rsscotty]

The air filter sticking out of the engine grill is nothing more than an attempt to get the coolest air possible into the engine intake. This configuration is for race cars, not street. We can turn the intake manifold around 180 degrees and have the filter facing forward for street car applications. Not a problem.............

[jamesjedi]

I think it is an amazing setup. I may use the adapters to allow me to use the common plenum. At least for now, until I can financially do the ITB's.


What is the best 964/993 intake to use? Obviously plastic, but which one?

[rdimarco]

I would also like to know how to adapt the single throttle body 964 manifold to SC or Carrera heads. I assume it flows better/more even than the carrera intake. Are intake port adapters available for this? Anybody know the throttle body size on the 964 manifold? (SC & Carrera butterfly is 63mm). Thanks.

[jamesjedi]

The adapters can be purchased from Rothsport. Perhaps others sell them.