How big can a 3.2 engine safely get?

[Allan Kelsey]

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.

[GH85Carrera]

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.

[OldSpool87]

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

[Rodsrsr]

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.

[Allan Kelsey]

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!

[msterling]

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.

[Dueller]

Originally Posted by Rodsrsr

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.

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?

[Bill Verburg]

Originally Posted by Allan Kelsey

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.

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

[GH85Carrera]

Originally Posted by Dueller

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?

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

[Allan Kelsey]

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.

[GH85Carrera]

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.

[mysocal911]

Originally Posted by GH85Carrera

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

The 993 engine doesn't have variable cam timing.

[Bill Verburg]

Originally Posted by GH85Carrera

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

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





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

[uwanna]

Originally Posted by Dueller

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?

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!

[Jgordon]

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.

[Allan Kelsey]

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?

[uwanna]

Originally Posted by Allan Kelsey

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?

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

[Canada Kev]

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.

[uwanna]

Originally Posted by Canada Kev

I've thought a lot about this very question.

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.

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!

[Jgordon]

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.