How big can a 3.2 engine safely get?
 

So, like most of you, I am doing my homework as I plan an engine rebuild. I have decided that normally aspirated is going to be my approach to getting around 300hp (ideally) out of the Carrera motor.

As I weigh out the engine capacity increase options, I see ways to get to 3.4 or 3.5 using the 74mm crank, but are there options that can get me to 3.7ish and will they require a different crank or rods?

That led me to a second the question: how big can the air-cooled motor get reliably and keep A/C and not overheat in Texas 100+ weather?

Thankful for your input. :)

Allan.

http://forums.pelicanparts.com/uploa...1408724620.jpg

That is a slippery slope to spending big bucks. 300 HP is a challenge in a normally aspirated engine.

I am a long way from an engine expert but I suspect you will be much better off selling your 3.2 and buying a 993 engine and adapt that to fit.

No clue about HP limits, but that's a gorgeous color. I have a Marine Blue car that looks just like that in the sun.

Good luck

IMO the 3.2 is not a cost effective platform unless you go the forced air route. 3.6 with a chip, good exhaust and your easily at the 300 hp mark.

This is my first Porsche ownership experience.
In my opinion Porsche owners fall into 2 categories: Lovers and users.
I bought my car from a user that had no idea what he had, and have been slowly working my way through addressing the age related issues.

This approach has given me an opportunity to drive end enjoy the car while Im tinkering and I feel, for the weight and size of the vehicle that somewhere around 300HP would be fantastic in the car.

The current +/- 200 (at the wheels) is fun, but missing a little.
Its a little like the current FRS/BRZ's. Awesome platform, but missing a little bit more zip!

Cat delete, free-flow exhaust and a SW Performance chip will get you a few more ponies and better driveability for not too many $$. Removing weight can make a huge difference in performance.

Engine swap to 3.6L is on another level of cost but makes a lot of sense. Your used 3.2L will bring a good buck if it is in good condition.

I know this is going to sound like an ignorant question. But with only 15% more displacement the 3.6can easily yield arounda 50% increase In power.
why is this so?

I've seen a few 3.5s, but they all had various issues
If you want a big motor its best to start w/ a 964/993 block, there are multiple options for a build from there all the way to a fairly reliable 4.0

Technology.

The 993 has the variable cam timing, and knock sensors and a ton of other upgrades that only new technology can bring. Higher RPM and higher compression.

The new 991S engine is 3,800 cc & 395 bhp

I had thought about putting a 3.4L from a Cayman S with a PDK tranny in it, but that feels like sacrilege in an air-cooled body.

It quickly get silly expensive to do major modifications like that.

Just sell the car and buy a newer model 911. They got faster every year.

The 993 engine doesn't have variable cam timing.

993 does not have variable cam timing,

It does have a multi stage intake manifold various versions of which were used from 964 right up to the current 991

'94 and 95 993 used a 2 stage intake w/ a resonance flap

993 from '96 and '95 993RS use a 3 stage setup w/ a resonance flap and 6 variable length trumpets


http://forums.pelicanparts.com/uploa...1408742330.gif
http://forums.pelicanparts.com/uploa...1408742588.jpg

vario cam was introduced first used by Porsche in the 968 3 liter and then later used in the '99 996 turbo, and subsequently in other models

11.3/1 compression ratio with dual plugs and knock sensors, sequential fuel injection, bigger valves, resonant induction, and many more little things. Very high compression ratio is the easiest horsepower increase you can buy.
In the '70s the Detroit iron lost most of their punch due to the advent of unleaded fuel,
which required much lower C/Rs. They took most motors from 10-11/1 CRs down to
around 8/1CRs, and even most V8s couldn't get out of their own way!

I've had a 3.4, with 964 cams and a Steve Wong chip, for the last 9 years. It is as trouble-free as the 3.2 was, and I have about 260 hp. Twin-plugged with a higher c/r, extrude-honed, and a few other tidbits, and I don't think it would be out of the question to think 300 is within reach.

3.6 Swap - revisited
 

The other alternative to all this - is to go the 3.6 swap route. This is, no doubt, an issue repeatedly debated on this forum and to be honest, I think one that is best decided by the owner and their wallet??

That being said, available lower mileage 3.6 units are fetching $10K + these days and so, it might be worth revisiting this discussion in light of the modern cost to get to around 300HP at the crank?:eek:

One thing to consider, the resale value of your old 3.2 will help defray the cost. Back in '92, I found a low mile 3.6 for 6K, lucky I know. Sold my old 3.2 for $4000. Spent another 2k or so on home made engineering to make the 3.6 work in my '80SC. (there were no nice retrofit pieces, parts, and wiring to make it easy back then)
To build up a 3.2 to high horsepower, with reliability will probably run close to the $10K figure, and you then have a highly stressed 3.2 vs a stock engineered motor with great reliability. One more thing, with a 3.6, oh my the torque boost is spine tingling!
just my $.02

I've thought a lot about this very question.

I think one of the biggest issues with a 3.6 vs. a built 3.2 variant is that if you rebuild and enlarge your 3.2, you have what is essentially a new engine. If you're counting on the cost of a 3.6 and all the assorted conversion bits and such being similar to that rebuilt 3.2, what happens when that unknown big engine turns out to be a dud and needs to be unexpectedly rebuilt? Just ask Jeremy how he feels about that...

The other thing is that many 3.6s are of higher mileage and need a rebuild or will soon. I think that should be factored in, as well.

LN Engineering had a set of 102 mm cylinders (Porsche 911 3.2 102mm Nickies inc. 10.5:1 JE Piston set - Aircooled Nickies - Products LN Engineering) that when mated with the matching JE pistons I believe will make for a 3.7 engine. I haven't heard of anyone using these, so can't comment at all other than to say they exist.

Later 3.6s from the 993 have all sorts of technology that would allow for more/easier power, and owner convenience. Knock sensors that allow higher compression is one performance bonus, and having hydraulic valve adjusters is a pretty nice feature.

A rebuilt, twin plugged 3.5 should be able to run 285ish horsepower without much trouble or stress. I think one should be able to get to 300 or more on a later 3.6 with some minor freshening and some fuel system software.

It goes without saying that there are less and less good low mileage 3.6s available, all the more reason you MUST use due diligence to estimate the condition of a prospective motor. (leak down, history, reputation of the seller etc.) Yes it is easy to get burned, but if you find a good one, it's a pretty cheap price/performance upgrade.

Worst case is probably a top end redo and no case split, as these Mezger motors are
pretty bomb proof on the bottom end. The thing I like about the 3.6 motor is Porsche
fixed a whole lot of nagging negatives from the early motors. i.e. complete new chain tensioner design, added ceramic lined exhaust ports which reduced head temp 40deg C, fixed leaking valve covers, better rib design on heads for better airflow, twin plugs, sequential fuel injection.
And RELIABILITY!

Another point in favor of enlarging your current engine is that essentially whatever you do is bolt-on. Not sure how much originality means to you, but I like the idea that I have my original Ps & Cs, cams, etc. and could offer them to a future owner (haha, no, seriously...) if necessary.

But the fact that you would be running an essentially new engine vs.an unknown 3.6 is probably a better reason.

And it's more unique. If you hit 280 or 290 on a one of a kind built up 3.4 or 3.5, I'd think the cool factor makes up for the missing 10 hp. Unless you're that serious at the track, in which case buy the 3.6 and have someone build THAT up.

Yea, back in the early '70s(yes I am an old fart), I felt like you about the cool factor,
and built up a couple of 2.0s into 2.5 hot rod motors, with Vertex magneto ignition, 10.5/1 C/R
big Webers, cams, etc,etc. Had a lot of fun, and my share of headaches. That said, my 3.6 has been flawlessly trouble free low these 22yrs since '92 and is just a weekend ride. No more track/autocross for me! I think it comes with age, LOL.

Maybe rlane will chime in. http://forums.pelicanparts.com/porsche-911-technical-forum/826596-3-2-mfi.html

I do love the idea of reliability & I will not be unhappy if I don't get exactly 300hp.
285 will work & so would 315.
But I'm hoping for more than 250 and I don't think I need 350..
I have enough of a lead foot already. (Blaming my motor racing father for that genetic defect)

Yes, the unknown of buying a used 3.6 does creep over the line from risk to gambling..... :(

Allan, I have two 3.6 engines that have both required some work. The biggest expense however, came with the required parts to make them work in an earlier chassis with a 915. Right now, I am building a 3.0 twin plug, 10.5 to 1, PMO carb engine that will go in my 904. All in, that car will weight less than 2000 lbs. with a full tank of gas and my ample self. The engine will end up in the 250 to 270 HP range (this via Bob Jones at Jones Autowerks).

For you, cams, twin plug heads, a proper exhaust, and intake replacement or tuning along with a weight reduction regime for your car will yield big results at a significantly lower price tag than a 3.6 conversion. All depending on how much you do yourself.

If more power is your objective, sell me that car and go buy a 993. :)

It looks like you want a mostly street car, if so torque, tractability and reliability are what you really want, in other words a street motor.

Sure you can get 300 +/- hp from a built 3.2-3.4 but to do so you need cams and intake and exhaust and p/c and rods and oiling etc. that all work at higher rpm than you can now use, the engine will be way less tractable, ie the torque comes in higher in the rev range, the idle will be less stable all in all the car will be less derivable on the street at lower revs.

What you want is torque at a usefully low rev range

3 ways to get it, turbo(out because you want n/a), gearing(this is possible) displacement(3.6 -4.0)

You can build the 3.2 to 3.4 reliably but to use much happier cams you need pistons w/ valve reliefs and engine management that is less sensitive to intake manifold vacuum fluctuation than Motronic, if you raise the revs enough you will also need to address the crank, rods and oiing, to raise the cr you will want twin ignition. It goes on and on and is expensive.

Buy a 3.6( rebuild it if necessary) a stock 3.6 has 228-250 ft-lbs of torque at the flywheel stock(964 at the low end 993vram at the top) build a 3.8 at it gets better.

The engines come stock in a very reliable, hi c/r package, very tractable and mesh well w/ earlier chassis and transmissions you won't be sorry w/ the right engine installed correctly.

just for comparison;
'74 3.0 RSR 231lb-ft@6500
stock US 3.2 192-195 ft-lbs@4000
SC/RS 3.0 188 ft-lb@6500
964 3.6 228lb-ft@4800
964RS 3.6 239lb-ft@4800
993nvram 3.6 242lb-ft@5000
993vram 3.6 250lb-ft@5250
993RS 3.8 261lb-ft@5400
993Cup 3.8 279lb-ft@5500
993RSR 3.8 279lb-ft@5500

Go fast.......
 

+1 on this route. I pulled about 300 lbs off my 1980 SC Coupe and rebuilt the engine into a 3.3SS. Carrera heads, 100mm Mahle 10.1:1 pistons, LN Engineering cylinders, 964 cams, Electromotive XDi twin plug ignition and an early large port CIS system. Exhaust is by SSIs and a 2 in/1 out muffler. Haven't had a chance to put it on a dyno yet, but "seat of the pants" power seems to be quite good and the reduced weight makes for a better handling chassis. Cost to build this engine was around $12k with all the labor provided by myself. The only thing I farmed out was to have a valve job done on the heads by Xtreme Cylinder Heads in Florida. This engine is very comfortable on premium (91 octane) pump gas as it only requires 24-25 degrees advance with the twin plug ignition. It might even run ok on 89 octane but I haven't tried that yet. The ignition cutout is set at 7500 rpms. I haven't bumped up against the cutout yet, but I have buzzed it up to 7K a time or two where it was still pulling strong.

Change out those SSI's for headers with 1-5/8" primaries and you'll see an even bigger improvement - SSI's are fairly restrictive for a 3.3L engine (better suited for <3.0L), especially with 964 cams. Add a wong chip and you're set!

What he said
 

I thought about the headers, but I needed to keep the heat functional. The SCs don't use a "chip" all of that came along in 1984! If I can find a set of appropriately sized headers w/heat I might go that route. Also, at some point I will most likely replace the CIS with a set of 46mm PMOs, but for now I want to keep the fuel efficiency of the injection. After I get it on the dyno I will make decisions about more work on this engine.

Bill,
I think you hit the nail right on the head! I was thinking most of the things you said,
but could not express it as well as you. After 22yrs with a 3.6 addition to my '80SC,
I am still pleased with it every time I turn the key! Great street car, and trouble free.
Only addition I covet would be a G50, but that's too much surgery and dollars.
Grant

So, a recent investigation of gently used 993 engines shows asking prices around 10K.
Assuming I can find one with an accurate representation and genuinely doesnt need any additional love, other than an oil change - what is the additional cost to mate it to a 915 tranny and install?

Allan, building a big engine is big fun and costs big money as well. My 3.7+ engine cost more than 40K with tuning. It's not for the faint of heart or pocket book. I say a 3.6 is the way to go, but your still looking at over 15K.

http://forums.pelicanparts.com/porsche-911-technical-forum/409427-my-new-track-engine-debut.html

Good Luck, and beware the "Slippery Slope".

I would love to flat top piston your engine and throw a monster turbo or twins on it.

Did it make 400hp? Couldn't find.

Instant-G
has a cost estimator

easiest and cheapest as any of the OBD1 3.6 engines, these come from any n/a 964, '95 US 993, any n/a RoW 993, more complicated and expensive is the US '96 -98 993.

to further complicate the issue any of the OBD 1 DME's have used replaceable push in chips, '96 US 993 DME was a one year design 2 chip design that can't be reflashed, '97-98 DME has a soldered in chip set that needs to be removed and re-installed to reflash, this is not something most owners will wish to attempt.

so best advice look for a 964, US 95 993 or RoW 993, the best fit is the US '95 non vram 993, both of the others fit but the tall intake on the 964 causes issues as does the bigger vram manifold both work

The one I like the best in this chassis is the US '95 993

my '76 C3 w/ 964
http://forums.pelicanparts.com/uploa...1408916604.jpg

my '76 C3 w/ 3.8RS
http://forums.pelicanparts.com/uploa...1408916727.jpg

my '76 C3 w/ '95 US 3.6
http://forums.pelicanparts.com/uploa...1408916769.jpg

Here's the pieces/part to "git er dun". just one of couple of folks who offer this.
You don't need to buy all the stuff, if you're mechanically inclined, and can read a wiring diagram, you can fabricate some of the stuff on your own. The pricey engine tin package can be easily done by you. One caution, if you want to keep AC, '96 motor Vram intake assy will not allow room for an AC condenser. I would look for a good 964, or a 993 earlier than '96.
If you do a google search on this forum, you will find tons of info on this swap that have been done by some very resourceful Pelicans.

993 (3.6L DME) Engine Conversion to Porsche 911 / 915 By Patrick Motorsports Porsche & Mid Engine Performance Specialists

The 95 993 3.6 is the way to go. The 964 has an externally balanced crank and solid lifters that require adjustment.

Mike,
I watched your build with great enthusiasm and am SO grateful that you were willing to share your build journey, it was an great learning opportunity for me to watch!

Thank you.

Wondering how you came up with the 300hp target. Are you feeling like your car needs a transformational kick in the pants to be exciting? Or do you want to keep it somewhat original but still have a lot more than you did before?

Can't help but be impressed with a lot of the dyno charts on Steve Wong's website. Pick your recipe... but I'm seeing a lot of ways to spend $10,000 (price of 3.6 you quoted) and end up with one hell of an enjoyable, revvy, original, rebuilt 3.2. Slight overbore, high comp, twin plug if you need it, 93 octane chip, exhaust, arp headstuds for some more revs, street cams that keep power down low...

I might be in the minority but my feeling is that as long as a car is not embarrassingly slow, I'd rather be able to wring its neck every day in every gear than to have too much motor or to stretch my budget and not be able to pay as much attention to longevity as I do bling in my build.

Of course there is no way on earth you'd be unhappy with a 3.6, I'm just thinking there are plenty of tried and true ways to hop up the motor your car came with.


A few snippets from 911chips.com

Here is Jeremy Dixon's '87 Carrera which was rebuilt from 3.2 liters to 3.4 liters with a Malhe 3.4l 9.8:1 piston and cylinder conversion set. The engine is modifed with the following: 1 3/4" B&B headers, ExtrudeHoned intake manifolds, FFenSport bored throttle body, 993SS cams, ARP rod bolts, Competition springs and retainers, and a Magnaflow muffler. Along with our custom chip for a 3.4 conversion programmed for 93 octane fuel, the engine produces a peak of 244 hp at the rear wheels.Factoring a 15% drivetrain loss, the engine produces 288 hp at the crank.

The following run is from an '87 3.2 Carrera built by Autometrics Motorsports in Charleston, South Carolina on a Dynojet 248c. The engine modifications include the following: 10.3:1 cr pistons/cylinders, 964 cams, and headers with racing mufflers. The chip is a custom 911Chips program for the engine combination and 93 octane fuel. The engine produces a peak of 234 rwhp with our performance chip. At 6200 rpm, factoring a 15% drivetrain loss, this engine produces 275 crank hp.

The following runs are from an '84 3.2 Carrera on a Dynojet 248c. The engine is modified with the following: Euro compression pistons, racing headers, megaphones, ARP rodbolts, 9K valve springs, a racing valve job with polished ports, and Webcam 20/21 cams. The chip is a custom 911Chips program for the engine combination and 93 octane fuel. The engine produces a peak of 238.8 rwhp with our performance chip. At 6200 rpm, factoring a 15% drivetrain loss, this engine produces 281 crank hp.

r-mm
Those are some very encouraging numbers and feel very attainable!
I dont intend to race the car, maybe a track day or 2 each year.
Otherwise, Im just a spirited driver with an enthusiasm for engine modification and a goal to improve the horsepower to get closer to 300hp at the crank. I chose that number because I have driven other - similar weighted vehicles - which ran a little under 300hp and it felt like a wonderful balance between power & weight.

Finally, for me, the payoff is also in the sound of a modified flat six in the upper rev range..... so delicious!

That jeremy dixon engine build looks spot on Im in the same boat as you allan engine choice wise and I reckon that looks like the best all round compromise. No aftermarket ecu required either no twin plugging cos our fuel on this side of the world is good high octane as well.