Cams for a 3.2 Engine?

[hoss4659]

In the process of installing Sal Carceller's MAF conversion on a 3.2 engine we found some failed valve guide seals and questionable valve guides. So the heads are going out for new guides, valve job etc. In the time-honored spirit of "As long as we have the engine torn down, we might as well . . . ", I am wondering about changing cams among other things.

The car is set up for touring, not track work. My interest is in improving low and mid range torque, not top end horsepower. The car already has SSI headers and is exempt from smog inspections. Three things occur to me:

1. Adding spacers between the intake manifolds and the heads to increase the intake runner length. May be counter productive as it moves the injectors and this may have negative consequences.

2. If the cylinder walls are damaged, which is highly unlikely, bumping the displacement up to 3.4.

3. Changing the camshafts. I am devoid of knowledge about alternatives and would appreciate inputs from the Pelicanite community. 964 cams appear to be to be a popular alternative. What are their characteristics?

Thanks

[Elombard]

Great question, I would seek the consult of some of the serious pros....not sure how willing they are to share if you are not using their shop. Perhaps you could get with Patrick motorsports and have some of the work done there and get advice as they are in AZ?

I am sure some of the folks here will give you good advice.

My .02

it seems like Porsche would of had to make some compromises with cams in the 80s to ensure grocery getter drive-ability, emissions compliance, and reasonable gas mileage. Probably with the 964 design and advances in technology there were slightly less compromises. IMHO though the twin plug 3.6 is a bit different motor and the Porsche engineers did a massive amount of research to get the cam optimized for that set up.

Plenty of folks have used the 964 cam grind in the 3.2 and reported good results.....


If I was rebuilding my 3.2 I would reach out to the Porsche specialist cam grinders and talk with them about their recommendations. I think they have worked with some of the air cooled Porsche experts to develop grinds that shift some of the compromises toward performance. Especially since you are not really concerned with emissions and gas mileage and you are willing to compromise a little drive-ability when leaning toward performance.

That said - I would not go too far (the cam grinder will be able to help) because your not tracking and you are running SSIs which are I think proven to be a little too small on a 3.2 for ultimate performance. However with your intended use a great choice.

Again the cam grinder will be able to help but its a system and you cant put Daytona 24 hours winning cams in an otherwise stock motor and get satisfying results. The cams need to match the rest of the system.

[Elombard]

Also, I think Steve Wong would be a great resource he has done a ton of custom chips with dyno work on all sorts of 3.2s and might have suggestions if you are buying his chip.

[Rodsrsr]

Pretty sure Sal's MAF kit already comes with a tuned chip, as that is usually a necessary component for the MAF conversion. Besides, Sal knows these DME systems inside and out, so fine tuning a chip would be a no brainer for him. FWIW, I used EBS racing to cut a web 20/21 grind for my 3.2. It'll increase mid range and top end, plus you get the added bonus of it loping like a V8 at idle. 8-)

[Elombard]

good point, I forgot he was putting Sal's kit on there, he probably has some great advice on cam choice.

Rod how do you feel about a 964 grind? I know you have seen a bunch of these.

[GaryR]

Originally Posted by hoss4659

In the process of installing Sal Carceller's MAF conversion on a 3.2 engine we found some failed valve guide seals and questionable valve guides. So the heads are going out for new guides, valve job etc. In the time-honored spirit of "As long as we have the engine torn down, we might as well . . . ", I am wondering about changing cams among other things.

3. Changing the camshafts. I am devoid of knowledge about alternatives and would appreciate inputs from the Pelicanite community. 964 cams appear to be to be a popular alternative. What are their characteristics?

Thanks

Speak with John at Dougherty Cams once you know what the rest of the engine will be.

[gliding_serpent]

I have gone down a similar path, so I will pipe in.

The "best" cam depends on what you want. How much Hp? what compression? What fuel? twin or single plug? What is your budget? Redline to the moon or keeping the stock peak hp (around 6200rpm)? You have no smog concerns, so you have lots of options. If your goal is to keep near stock rpm for peak power...

1. Leave the intake runner length alone. They are tuned to produce peak volumetric efficiency (VE) at a very usable powerband for the street (max hp at about 6200rpm), which seems to be your goal. Lengthening them would push down the powerband (max volumetric efficiency at a lower rpm), but the efforts and issues with injector position would negate any advantages. Leave it alone. Maybe get it flow tested, and consider extrude honing if your flows are highly variable between runners. Debatable power benefits. Now, given the precision of Sal's system, IMHO you should consider extrude honing, especially if you expect big hp gains. This will prevent one cylinder from running a little richer or leaner.

2. My cylinder walls were starting to show mild wear. I used it as an excuse to go 3.4. I opted for single plug Max Moritz pistons. I cheeped out on twin plug at the time.

3. 964 cams are a touch more aggressive than sc/3.2 cams. A bit more overlap. Good for emissions (high overlap is great for power, bad for emissions). They are good for maybe 5hp over stock. Will not change your peak hp/VE much. I took this route.

Here is another way to look at things: Assuming your goal is stock Redline and midrange

1. Intake:

a) air filter: the cone intake for Sal's MAF is as good as it gets to reduce intake restriction.

b) AFM/MAF: Again, Sal's system is as good as it gets for flow (carbs are a different beast and will not be addressed).

c) Intake manifold: Plenum length tunes the VE of the intake (longer tube, max VE at a lower RPM as you know), just ensure they are flow balanced as noted above. I would leave the lengths alone.

d) Throttle body: Consider a larger throttle body to match your more open intake if you plan on significant HP gains, otherwise the flow gains of the MAF/cone filter might be minimized.

2. Engine:

a) Displacement: If you want more midrange, you will get if from more displacement. Displacement gives more top and bottom end too.

b) Cam profile: The more aggressive the cam, the dogma is that the higher a RPM you will need to see the max benefits (as peak VE gets pushed into higher rpm values).

c) Cam timing: What some folks forget is not just the cam, but the cam timing. You can have one cam, and through adjustments in cam timing, you can push the VE up or down the rpm range. If you want midrange, put the cam timing to a higher value. Talk to a pro on this.

d) Compression: higher compression increases VE (power) across the powerband. But with single plug, don't expect to get much above 9.8:1 or maybe 10:1 at least on 91 pump gas (stock is 9.5:1 on our USA cars).

e) Ignition timing: To properly/safely run high compression on 91 octane, you need twin plugs (and appropriate shaped piston tops). This gets very complex to explain. Talk to Sal on this. Man knows his stuff.

f) rotating resistance: lessen the internal resistance to rotation of your engine (boat tailing,lightweight forged rods, light clutch/flywheel, etc. The less power your engine wastes on internal friction losses, the more hp it will have to transfer to the wheels. We are reducing losses, and this helps midrange... and everything else. This is the key to engines that are getting the really big numbers. It is also $$$$ for the most part (although a lighter flywheel and clutch can be a easy way to reduce internal losses).

g) Injectors: you need higher capacity injectors once your engine starts to make a lot more power. Sal has you covered there. They also have better midrange and low rpm performance than stock due to better spray patterns at lower loads. Mind you, you may not see those results on a dyno.

h) other things out of the scope of one post (porting, larger valves, etc).

3. Exhaust

a) headers: longer primaries help midrange. 31 inches seems to be a sweet spot. Most aftermarket headers have 31 inch primaries. Avoid ones that are shorter if midrange is your goal. Smaller diameter primaries also help midrange. The cost is high rpm power in both cases. Your SSI's will be fine, but if you expect over 250hp, consider stock headers, or something else with a 1.5 inch internal diameter. Mind you, SSI cars can make over 300hp, but I think to get much over 270hp (we are talking at the crank), it needs to be done with the help of internal resistance reduction (or that is my take on it) otherwise returns on investment will be diminishing.

b) Muffler: a crossover helps midrange power. An overly open muffler hurts midrange. A good muffler design will have both an internal crossover effect, and a proper baffle design to help both power and midrange. A Dansk Sport is a proven option.

4. Gears: shorter ratio gears (or final drive) multiply torque. This helps you across the power band. Thing is, you can save money and just shift down a gear for a similar effect. Playing with gear ratios IMHO is best reserved for a car on the track or a b roads monster, or classically, one with a narrow power band (traditionally, peaky, high rpm race engines) and you really need to do your homework and know what you want. Talk to Matt Monson, he will not led you astray.

5. lightness: adds performance at any rpm. The easy weight reduction is also free.

So what is the best cam? It depends is the answer. I would go with a mild upgrade. 964, or 20/21. This would pair well with a mild 3.2 or 3.4 with single plugs, 91 gas, the MAF/chip, stock headers or SSI with a sport muffler. Expect 250-275hp depending on your choices.

Now build a hotter 3.4 with twin plugs, high compression, and you will want more cam to get max hp (275-300hp).

Now build a 3.4 "spinner" (race engine) with all the bells and whistles and you will want a very aggressive cam. A 964 or 20/21 would hold you way back.

[gtc]

With the stock pistons, 964 cams are a safe choice.
993SS cams are supposedly at the limit for valve clearance.

[Rodsrsr]

Originally Posted by Elombard

good point, I forgot he was putting Sal's kit on there, he probably has some great advice on cam choice.

Rod how do you feel about a 964 grind? I know you have seen a bunch of these.

I've heard good things about the 964 grind in the 3.2. I believe it is slightly milder then the 20/21 grind. For what the OP wants, its probably a good choice.

[scarceller]

Here's my list of suggested off the shelf cam grinds for the 3.2L with my MAF system, these are in order of mild to more aggressive:

1 - 964 OEM
2 - WebCam 20/21
3 - Dougherty DC20
4 - Dougherty DC21

Any of those cams will work well with my MAF system, even the DC21 runs perfectly without any lumpy idle or cruising issues.
If you just want a small increase use the 964 cam as thee are easily sourced. The other 3 are custom grinds and I suggest ONLY getting these if ground on fresh billets, do not have old cams re-ground.

I'm currently testing a build with DC43-112 cams, very aggressive cam for the common plenum in the 3.2L motronic. We'll see how this cam does in the next few weeks. This motor currently is a twin plug 3.4L 10.5:1 comp with DC21 cams and is at 280 crank horse. We are looking to break the 300HP mark with the DC43-112 cam, hopefully this cam will open up the breath-ability at the hi-RPMs for this motor. We'll see.

I highly recommend Elgin cams as well but those above have been used often in the 3.2L with positive results.

[scarceller]

Agree, 964 or 20/21 cams are a safe choice for stock setup

Originally Posted by gtc

With the stock pistons, 964 cams are a safe choice.
993SS cams are supposedly at the limit for valve clearance.

[OffCamber00]

I have 964 cams on my 3.2 with stock intake and AFM. Really woke up the top end when combined w/ headers and a Dansk 2/2.

[tratza]

Great ideas. Thanks guys for helping me continue to spend more money.

I've been running an Autothority MAF since 1993 and John Dougherty ground cams (can't remember the grind but think its the 20/21) since a full rebuild in 2005. Only other modification has been a cat bypass and added a second exhaust outlet on the right side of the stock muffler. Its been twice dynoed at an average of 220 hp at the rear wheels.

BTW, The MAF has only needed a potentiameter (about $90) since the MAF was installed. Its also passed air emission tests regularly. I highly recommend it.

[scarceller]

In addition to cams the next best area is to address the intake track, in priority order:

1 - Bore the throttle body, cheap to do about $150-$200
2 - Extrude hone the intake, about $800
3 - If you are having the heads done send them to a shop that can also flow bench them and rework the shape of the intake and exhaust ports.

I've seen improvement of up to 10% in torque/HP if these areas alone are properly done, especially the head flow work.

My personal opinion is that money is better spent on air flow improvements than displacement upgrades. I'm not saying displacement does not mater, I'm just saying that improving air flow is a better place to start. If you can do both displacement and air flow that's yet a better option. My point is that if the motor can't breath properly through the intake track then no point increasing displacement.

I've worked on setups that went from a 3.2L to a 3.4L and during WOT hi-RPM we saw near -2PSI intake vacuum, that's 2PSI free boost left on the table, simply because the intake track was not addressed. When you dyno a motor or even pull a WOT street run it's a very good idea to monitor intake vacuum during the run.

[Bill Verburg]

Originally Posted by hoss4659

.....
The car is set up for touring, not track work. My interest is in improving low and mid range torque, not top end horsepower. The car already has SSI headers and is exempt from smog inspections. Three things occur to me:

.....
Thanks

Cams can generally only add hp and torque at raised rpm. They do this by increased lift and duration, increasing overlap w/ the use of header tuning spices the installation.

The only thing that raise hp/torque across the rev range is
increased displacement
increased compression
optimized mixture and timing
gearing via trans or tire

it's theioretically possible to raise hp/torque by using a cam w/ increased lift alone, but Porsche didn't leave much if anything on the table for that to happen

Oe smog cams which have been the norm since the mid '70s have very little overlap timing and very little duration. This is for emissions and fuel economy as this type of cam promotes complete combustion in the engine. what little fuel that doesn't burn in the engine is consumed by SAI and catalytic action in the exhaust.

The factory didn't get around this cam choke point until the late vari cam designs hit the road. These have the zero overlap short duration cam designs used in previous smog motors but also have secondary lobes that come into use at higher rpm, these secondary lobes have the high lift long duration timing needed to produce impressive #s at higher rpm. High rpm power is further enhanced by more efficient 4 valve head designs.

Variable intake geometry like exhaust tuning can enhance torque in a relatively narrow power band, the two common such designs are the resonance intakes first seen in the 3.2 Carrera motors and still used today on all the flat 6 water cooled motors and the vari ram used on the '96 -98 993.

My best addvice for low-mid torque is increase displacement
3.2 is nice 3.4 is better and 3.6, 3.8, 3.9, 4.0 are better yet.

The bigger the displacement the more cam can be used w/o sacrificing low rpm power

[Spumato]

My vehicle is a MY1974 that has a rebuilt MY1983 SC3.0L transplant.

When we designed and specified the engine, we decided to add real, not ground, 964 cams. Also, with the stock pistons being 9.3:1, and the engine being bulletproof, we wanted to have some fun while ensuring longevity. Titanium valve springs were added to handle the extra load of the more aggressive cams. We also reinforced the engine with ARP head and rod bolts, added a lightweight flywheel, replaced the ignition with a pentronix unit, added a 3.0L fuel pump, Carrera chain tensioner upgrade, reinstalled the SSI's and added an M&K dual in, dual out muffler. I would do this again in a heartbeat! She has been more fun to drive than I could have imagined!!!!

[stan911]

I have 993ss cams on a 3.4, that makes a great engine.
Lots of torque and reving like a big S engine up to 7000 rpm.
About 270hp (depending on dyno) with headers and mK exhaust

[Spumato]

Yeah, not sure what my total HP is, but mine wraps hard through 7,300 rpms!

[scarceller]

Here's a 3.2L with a lot of head flow work and custom cams. This was built by Bob Farmer who is a master at flowing heads, the head flow work and port shaping and polishing took about 5 days. It still runs stock AFM and Air Box. He then used my services to create a custom chip for this motor.

I do not know all the special sauce but this 3.2L had amazing results, Bob has his own in house engine room and dyno, results are as seen here:



Basically it's a stock 3.2L US setup with very careful attention to air flow improvements, matched cam is cut from the airflow bench work so the cam matches what the head's flow.

This motor hit 269 Crank Horse Power and it's a basic US 3.2L, single plug with low compression ratio.

[stan911]

Originally Posted by scarceller

My personal opinion is that money is better spent on air flow improvements than displacement upgrades. I'm not saying displacement does not mater, I'm just saying that improving air flow is a better place to start. If you can do both displacement and air flow that's yet a better option. My point is that if the motor can't breath properly through the intake track then no point increasing displacement.

I am surprised they are not more 964 plenum installed on 3.2 engine. It is probably better than honing the 3.2 intake.
it is something I'd like to do on my 3.4 if I had the skills.