You are correct there isn't much information around that is backed up with data regarding cam choices for 3.2/3.4's with the standard 3.2 inlet manifold. I was hoping to get Neil to talk more about this with my attempt at leading questions earlier but he stayed professionally coy!

This tread is probably the closest I've seen to giving some reasoned thought on cam selection for this application. They ended up going back to DC21's after trying a few others:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/871561-1985-3-4-build-using-maf-279-56-hp-237-63-rwhp.html

Here's where I was going, based on this build and some similar ones. Nothing is set in stone but like I said, I'm hoping to copy other peoples recipe for a strong 3.4-
http://forums.pelicanparts.com/porsche-911-technical-forum/962997-1984-911-3-4-sleeper-hotrod-end.html
So what was the formula for my 3.2l? From intake to exhaust... here it is (sort of):
- MAF/injectors/dme/chip with cone intake from Sal Carceller.
- 91 octane fuel
- single plug
- 66mm enlarged throttle body (stock 63mm)
- no extrude hone for intake runners
- 964 cams
- max moritz 3.4l pistons with 9.8:1 compression ratio
- custom 1.5 inch internal diameter headers (i had them built to my spec... with heat)
- custom muffler

LOL. I started the exact same location you did with the same "recipes" for inspiration!

I ended up with:
ARP rod bolts to allow 7000rpm safely
Mahle Motorsport 10.3:1 98mm pistons that were further fly cut for more valve clearance
Existing cylinders were over bored 3mm and re Nikasil'ed
Twin plugged heads
993SS cams
Balanced
30-2 crank wheel
Motec M130GPA ECU
Direct fire of 12 Nippon Denso CoP's
Full sequential with Bosch 4 hole fuel injectors 0280 155 868's (running at around 70% duty cycle at full load)
AFM delete. Load modelling based on manifold absolute pressure, air temperature and throttle position
Twin knock sensors mounted on 964/993 knock bridges attached to the underside of heads
Twin wideband O2 sensors to allow each cylinder to have individual fuel and ignition trims
Fuel pressure, air intake temperature and throttle position sensors
Cam position sensor to correctly time the direct fire ignition and injection
Clewett plug for the now vacant distributor hole in the crankcase!
BBE 1 5/8" headers with hotboxes with generic Porsche outlets to bolt to a Dansk Motorsport 2 in 1 out muffler. ie not the specific 3.2 ones BBE make that limits you to there propriety muffler.

First thing you should be alert to is the slippery slope!

Because I started off thinking I'd either have a Wong special chip or maybe a Sal MAF conversion, John Dougherty recommended the 993SS as the most the AFM could cope with. However the project scope grew and eventually the limitations of the Motronic fell away and I could have easily gone to longer duration cams like the DC21's or even DC35's. What has surprised me the most is how mild and civilised the 993SS cams are in this build with heaps of bottom and mid range and a touch extra on top as well. This engine is definitely less peaky than a standard 3.2 or a 993 for that matter. I wasn't expecting that!

The engine is wonderful. Revvy and responsive and power is smooth and linear. It feels like a modern engine.

Probably the second thing I'd do better next time is more carefully plan my build before I start to avoid having to do things twice and the cost that incurs.

I suggested a fresh look at what’s optimal for your engine vs what you had on hand. I know there’s room for improvement over a stock 964 cam. I think the DC35 maybe a bit much for a street car so in my opinion the truth lies in the middle somewhere.

The DC21 cam is considered a sport 964 cam. Slightly longer duration than the SS cams so it falls somewhere in between the 964 and DC35.

I strongly suggest you contact John at Dougherty cams and discuss what’s important to you and your setup and see what he suggests.

Its been a while, but my ask of Doherty was:

Application = Hot Street
Displacement = 3.4L
Type_Of_intake_system = Individual Throttle bodies
Type_Of_Exhaust_System = Small Headers with muffler
Head_modifications = Heads and rocker arms have been rebuilt by Steve Weiner (Rennsport systems)with new everything and titanium retainers, dual plug + CoP

Engine is using the Mahle 98mm p/c's with the 10.3 compression.

Intakes are the PMO EFI, exhaust is Eisenmann, crankshaft is Turbo 74.4 mm.

Engine management will be EFI, not certain as to brand but good chance it will be Motec.

Car use is street, 6 speed G50, largely touring. Not concerned about maximum performance but want driveability and reasonble fuel economy and reasonable power

His recommendation was the DC35

Dennis

My question.. you mention the use of max moritz 3.4l pistons several times.. as I recall the "MAX Mortiz" pistons, as I know them, are basically a 98mm piston with an offset dome to accommodate CIS, typically used to create a SS 3.2 from a 3.0 You are building a 3.2 based 3.4.. so yes, also 98mm, but why would you use this piston, as your motor is motronic? Did I miss something?

Dennis,
Why this thread is different to most is that we are trying to figure out what cam options are suitable for street use using the standard 3.2 manifold and single throttle body on a 3.4 converted 3.2. Using ITB's like you have, opens up the range of viable cams significantly.

This thread, although old, has some interesting comments from Steve Weiner on this topic:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/138447-individual-throttle-bodies-vs-flowed-carrera-intake-manifold.html

I'm pretty sure Mrs Mortiz named her son Max rather than "MAX". He when on to become a Porsche dealer in the 50's and later a very successful racing team owner. His company, among other things, developed big bore kits and a distinctive style of piston crown that worked well with single plug heads. Essentially the top of the piston has a big flat face that is bevelled at an angle away from the spark plug.

These pistons are popular for 98mm conversions with the only real difference between the 3.0 to 3.2SS and 3.2 to 3.4 applications being the size of the wrist pin bore, 22mm & 23mm, to suit the different conrods in these engines.

These pistons, like all others, work with any style induction system. The combustion chamber doesn't care if it's CIS, carburetted, MFI or EFI as long as the fuel is atomised and in roughly a combustible proportion with air.

So in a nut shell, MM pistons are just well worn path to increasing capacity and work well with single plug combustion chambers.

"One of the most popular conversions is the 98mm “Max Moritz” wedge-dome set. This is a 3.4 litre upgrade with a 9.8:1 compression ratio that has a special dome shape compatible with CIS and Motronic engines."

---Another item that I obtained for free, along with a 3.4 Mahle cylinder set, so I will use them unless there is a compelling reason not to.

I will hold off on calling any of the profesional suppliers like Neil, John, etc until I'm actually ready to buy something. While I appreciate everyone's input and advice on this thread, I don't believe in taking up people's time at work until I can reciprocate with cash.

The DC35 cam is a lot like the 964 cam spec but it has a centerline of 110 deg, this creates more overlap at TDC when both the intake and exhaust valves are open. The stock Air Meter (AFM) may not like this and will likely cause some idle issues as well as low RPM cruise issues.

My MAF system will not have much problem with this cam choice.

Another good cam is the DC25-964 cam also a 110 LCA cam but a little less duration and better for the 5800-6000RPM peak torque sweet spot in the 3.2L engine.

Oh, I'm sorry, I must have not been clear... and having been at this for about 35 -40 years I think we all know who Max Moritz is and the details about his pistons and 98mm, why, where how..blah blah... Anyway, we've all read that. And come to think of it, believe I still have a couple of sets on the shelf in the basement.

Funny too.. re: spelling, I deal with another Portal on a daily basis called MAX.. so yeah, I sure you're correct in that momma named him Max!SmileWavy

My primary ask was why use theses, if obviously if its 3.4 build, your not using CIS.. and the read is your contemplation with what cam to use. I guess with the motors I've been involved with if we're going to 3.4, we're looking at adding some compression.. didn't see that you were staying Motronic.

I am.
Remember, I'm at the bottom of a steep learning curve so when I ask a question, it might be part of a bigger question that I'm not aware of. I do appreciate everyone's input and suggestions.

Never feel awkward in asking questions about something you may not know anything about. We have all come from that place. I'm still there.

I learn something every day. If I leave the office and don't feel I have learned something, I must have not done something right.

""""My primary ask was why use theses, if obviously if its 3.4 build, your not using CIS.. and the read [I]I guess with the motors I've been involved with if we're going to 3.4, we're looking at adding some compression.. didn't see that you were staying Motronic.""""


BTW, these are engines not motors. Call them what they are. Internal combustion "motor"??

Funny stupid thing I have about building engines and something that gets in my craw, I hate when I see engines been built and used as a tool bench. I tell my people, only have the tools on the bench that you need to do what you are doing right then, all the others are put away. Having good building practices is important. I laugh when you see a bench in the morning clean and clear and by the end of the day you cannot see the bench and the person is working in a 6" inch square area.

Another is calling the cylinders jugs and pistons slugs.

How did I get off pistons onto this rant???? Been along day and its not over!!!

I’m with you Neil.
I was taught electric motors and combustiin engines and sometimes it bugs me too. Kinda like your and you’re and there, they’re, and their.
If English is your native language then you get a pass but everyone else was taught this in school and should know the difference.
Don’t get me started on spelling either. Hahaha

Oh yeah I’m in the call John whenever you’re ready to move forward camp because if you ask 5 people you’ll get 5 different answers so I’d go to the man to clear any confusion.
Tony

Just an FYI...
I am also modifying my 3.2 to 3.4, but I'm keeping it a single plug.
I am buying a new set of 3.4 P&C using the Moritz style 9.8 compression, as that is meant for optimal single plug ignition.
I'm also going with 964 cams, as that has been recommended to me by about a dozen different Porsche air-cooled racing shops that I've called around on.
I also went with upgraded valve springs and retainers, as I plan to push the redline to 7000.

The good thing about the 964 cams is that they are a 'drop in' replacement and I would just need to request my ECU chip replacement for my setup... as they have refined the programming for quite a few engines using the exact same setup.

This appears to be a common and desired upgrade for these engines. But the parts used are "out dated" in my opinion.

We recently did the exact same upgrade for a customer and used the same internals. The result works, but it inspired me to take a serious look at this upgrade and what it needed.

The limitations of the wedge piston are many, particularly weight, valve lift and CR. I had a long conversation with Steve Wong and he told me there is no limitation to what can be built that will give cause to the engine mapping needs. This opened the door for us to consider new internals.

What does the 964 cam give you over the stock carrera cam or say a DC30?

Thanks,

Chris
89 Carrera 3.2

I think it’s great that you and other enthusiasts continue to develop these engines.

I was able to find another tired but running 3.2 for cheap. So while it moves me financially further away from a high performance build, it gives me another engine for the future. I’d like a ‘66-912 with a 3.2 - one day...

So Neil,
If you had a 84' to 88' Carrera that you only drove on the weekend, what would you do to the engine?

Yah can't just say put a 3.6 in it either! :)