Just another 3.2 Short Stroke
 

About 6 months ago we started an engine for a back dated wide bodied 911.
The engine is as follows.

3.2 Carrera case tumbled and treated with caustic soda to replicate early mag case.
The case has feed mods for extra crank oiling
Shuffle pins
GT3 main and rod bearing with dry film lubricant
Turbo pump
Cross drilled crank
Pauter rods
Racing Iwis chains on a properly fitted intermediate shaft.
Supertec head studs
Mahle factory 98 mm cylinders reconditioned by Millennium and machined for cooper sealing ring by Supertec
10.5:1 JE pistons with tool steel wrist pins, ceramic coating and dry film skirts
3.2 Carrera heads with new valves (51mm X 42.5mm) and guides
Eibach racing springs and Aasco titanium retainers
Intake ports modified for MFI
DC 80 cams with 102 LC , cam are gun drilled for center lube with is fed through the two center cam journals.
Carrera tensioners and Supertec tensioner arms
Supertec reconditioned rockers (DU bushings, reformed threads, surfaced & dry film pads then Cryo treated)

More about the injection later.




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Like the case finish. What brand of valves are you using? Can you give us more info on the case mods for crank oiling?

The case is tumbled with medium steel peaces giving it a dark, rough surface (sort of like sand casting) then it is washed in a steam cabinet with mild caustic soda (sort of like Easy Off). If you try Easy Off oven cleaner be careful to apply it evenly and be ready to wash it off when it reaches the color you desire.

The valves are Swiss made InterValve prepped by polishing the stems.

Oil mod simply involves drilling the main bearing feed hole ( 7/32" or 5.5mm) from saddle to the main oil galley to promote increased flow to the #4 main bearing. The grooved and drilled (7/32) # 4 main bearing then transfers the increased oil flow to the #2 and #5 rods bearings through an additional hole in the crank.

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Henry,

You went with a basic 3.0L 70.4mm crank for this short stroke project?

Rods are basic Pauter 3.0L or did you choose the lightweight option with the 2 in. journals.

Did you choose to offset bore the small end of the rods to use Carrera style pistons or just use the typical compression height for SC style 98mm JE pistons with the SC crank?

Yes, It's my engine so cost was a concern.

Stock Pauter 3.0 rods. I just happens to have them in stock.

The same response here. We used stock Pauter 3.0 rods because I had them on the self.

Correction: They were actually 2.7 rods. I sent them back to Pauter to have them narrowed for use on the SC crank.

Henry,

Sorry my short questions may have come across the wrong way. Reason I asked about the crank choice wasn't to jab you for using a basic 3.0L crank. I just happened to notice that your list of components didn't state what crank you were using for this application. Didn't mean to imply, "hey what the hey, why aren't you using a Supercrank?"

Reason I asked about the 3.0L lightweight Pauter rods was also to see if you went that route, since I thought you might be building another screamer like the recent 3.1SS thread The shuffle pinning and center lube cams had me thinking you are going for high RPM capability.

Also asked about the rod lengthening via the offset pin bore to see if you wanted to get that better rod length-stroke ratio you've mentioned before, to take advantage of the lighter Carrera JE pistons and again serve the purpose of being easier to achieve high rpms. Was considering doing that for my motor.

Reason I ask the above isn't to critique your build choices. I'm still on the fence with my re-rebuild of the racecar engine to either 3.0 or 3.2SS. Time to _____ or get of the pot and select my rods & pistons since i'm sticking with a 9 bolt 70.4 crank. The previous 3.2SS was a baffling choice of:

std 3.0L crank (no complaint)
typ 3.0L Pauter SC rods but w/bored pin end for 23mm pins (nice rods!)
98mm Mahle Motorsport 9.8:1 carb/MFI Carrera comp height pistons (nice pistons, wrong pin height)
Bored & replated SC cyls (typically not a good idea)
Loooooong deck height of ~2.4mm (why?)
Single plug (odd, considering it uses Electromotive crankfire already- just add another board & plug holes)
Leaded race gas w/46mm Webers

Have no idea why that configuration was built. So, last go-around I made a traditional 3.2SS with "correct" rods (reconditioned Pauters w/new 22mm pin bushes) and new 10.5:1 98mm JE w/SC pin height, added some extra spark plugs. Then I somehow wasted all the bearings (except intermediate shaft- weird) & that took out 1 rod, scoring all of the crank, oil pump, pistons, cylinders, cams, cam housings. Big mess.

Sorry for the interrupt/comparison. Just bouncing around some ideas in my head about where to go with mine & of course you've got some lengthy experience with skinning the 3.2SS cat in various ways.

No worries Kevin. No offense taken.
I like the idea of using the GT3 rod configuration on the 3.0 crank.
The extra rod length (130 vs. 127.8 mm)adds to piston dwell and reduces rod angularity (side loading) all of which makes for a spirited engine.

If I had a clean sheet of paper (read mega bucks) the build would generally take a different form but like most everyone else, I have a budget.

A generous budget made the 3.1SS possible and I enjoyed every aspect of that build.
This on the other hand is "Just Another 3.2 Short Stroke"


Cheers

Henry,
I am curious what is meant by "a properly fitted intermediate shaft."
Regarding the Intervalves. I used them on my '86 3.2 engine. What led to the decision to polish the stems?

The gear on the intermediate shaft should be fitted to the drive gear on the crank.
By fitting I mean: achieving the appropriate backlash. Matching the numbers is close but not always close enough.

The InterValves seem like a very nice product with the exception of the shaft/ stem finish. They seem a little rough so we just polish them with the same tool we use to polish cranks.

ho hum ;)

why did you increase the valve size, particularly the exhaust? not being critical at all , I am genuinely ignorant of why and curious to know.

cheers

Increased flow at all RPM levels. The Carrera head has huge ports. I was trying to bring the ratio of port size to valve diameter in line with what I understand to be optimum about 80%.
I've tried reducing port size with our Venti-port system (with reasonable success) and now we're trying bigger valves.

Another beautiful engine... The cleanliness and attention to detail are breathtaking!

I was at the "Alméras Frères" garage yesterday in Montpellier and though they have a great history in Porsche racing, none of their engines look as nice as yours.

Looking forward to seeing the fuel injection setup, as well as the exhaust.

As always, thank you for sharing,
Ben.

Well, thank you for the kind words.

Here's a hint on the injection.

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Hi Henry - this may be a stupid question, but what are the key benefits or characteristics of short stroke vs. non-short stoke? Does it rev faster, feel any different?

Thanks

Covering this topic in general will require a semester of classes so I'll just cover the different between 3.2 Carrera and the Short stroke 3.2. The main difference is the relationship between the crank and rods.
In the 911 engine, Porsche found themselves stuck with a dilemma. Because they were a tiny car company, each engine development was an attempt to improve the previous engine changing as little as possible.
That meant every time they made the engine bigger, they compromised something.
In trying to keep the engine's external dimension consistent (to eliminate chassis changes) they were forced to keep the distance from the head to the crank consistent.
That meant every time they increased the stroke they had to shorten the rod (compromise the rod to stroke ration).
Starting with a 2.0, Porsche rod length to stroke ratio was close to 1.97:1 (2:1 being theoretically desirable) . As the engine grew that ration decreased. Finally in the 3.6 it was 1.67:1
The short stroke engine provides longer piston dwell time at & near TDC, which maintains a longer state of compression by keeping the chamber volume small. This has obvious benefits: better combustion, higher cylinder pressure after the first few degrees of rotation past TDC, and higher temperatures within the combustion chamber. This type of engine will produce very good mid to upper RPM torque.
The longer rod will reduce friction within the engine, due to the reduced angle (see illustration) which will place less stress at the thrust surface of the piston during combustion. These specifications work well with numerically high gear ratios and lighter vehicles.
There is also the issue of journal size. The 3.0 journal is smaller 53mm vs 55mm, making the crank lighter and allowing for a larger rod bolt that will still clear the oil pump.
This larger rod bolt increases the reliability of the engine at higher RPMs.
After the 2.0 (906 type), few if any, Porsche factory race engines were ever built using the 55mm, 3.2 Carrera rod journal configuration.
Some version of the 53mm journal was used in the 917, 935, 962, 956, 936 and on.
Even the recent versions of the GT3 uses the longer version of the 3.0 rod .
This rod length to stroke ratio was a major player in the design of the Supertec SuperCrank.

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A change in direction on my car has me leaning towards a non-ntercooled 3.6 turbo so this engine may be for sale. The custom inject has been sold but I can complete the engine with MFI or PMOs and exhaust or just sell it as a long block.
Let's talk

That is my dream engine. Awesome!!

What would the expected numbers be on such an engine? (HP,Torque)
Thanks, Rich

Here's what it could look like finished with MFI installed, modified stock air filter and heat.

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This 3.2 SS had milder cams (mod S), lower compress 9.5:1 and SSI exhaust and made 285 on Fat Performance dyno.

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Nice!

Wow. That is beautiful. Haven't seen rocker shaft screws plated. Cool. Probably all should be.
Mine have some slight surface rust. Now, if I could just win the lottery.

What the engine might look like with PMO carbs.

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Beautiful, lovely work, thanks for sharing

That thing looks amazing.. if I had a few bucks I would buy the long block. In the meantime I am working on my own 3.0 rebuild and I am stripping off every fastener etc to take them for yellow zinc plating. I am inspired to throw the rocker hardware into the pile as I see it was done here. I notice that the perimeter studs on this engine case were not touched.. Should I be wary of removing all my perimeter studs? Some of them are a little funky on the ends, and I am tempted to pull them to have them re-plated. But I won't do it if I am asking for trouble later on when trying to mate the halves etc.

If I could only find a car to put it in!
Rich

No worries about pulling the perimeter studs. They're basic M8 studs, nothing special about them. They get removed all the time when work is being done on the case halves. No different than removing head studs. Just be sure to threadlock them in place upon reinstallation. Blue/medium strength is fine. No reason to use red.

Just casually looking at this again for inspiration.. The picture posted of the carrera heads shows no chamfer of the lip for the 98mm pistons. Was it performed as part of the build or was it not needed? I have been reading up on this and it seems like there is no standard for this and its best done by matching the diameter and angle of the chamfer to the pistons you have for optimal deck and squish. However I would be curious to hear Henry's point of view on this .

A quick look at the pistons shows that we had the pistons made to fit the chamber rather than cutting the head.
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Henry ... Love the caustic treatment of the case. Can you share the cost of having this done? Would like to do this to my rsr engine based on a 993 case. Did you do this in house? Thanks.

A ha! The kind of thing I would never, ever notice.. so thank you for pointing it out. Any particular reason for altering the piston and not the head? The only thing I can think of is that it preserves the head to be used again someday in another configuration of piston size or shape.. or that it preserves your cylinder head volume... very interesting nonetheless. I assume shelf JE's have not as much of a lip around the edge before the dome starts.. I will have to wait and see what mine look like when they arrive and proceed accordingly.

After thinking about it a bit, certainly makes sense for the piston to be shaped to respect the existing shape of the head/combustion chamber. Since achieving desired comp ratio is sometimes a challenge, it doesn't make good sense to cut the head since that only serves to further reduce your comp ratio.

The std "off the shelf" JE 98mm 10.5 C/R pistons come built with the flat lip around the periphery of the dome. Here's a picture of a retired 98mm 10.5 I replaced this year.

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All done and ready for installation. It will be going in a 67 Vintage race car being put back on the street.

The beautiful distributor highlighted in picture 3 is made by Aaron Burnham @ Burnham Performance.

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Henry...

Could you comment on need/benefit of adding properly sized copper sealing rings to top of 98mm cylinders for this engine build? Are the copper rings used here a stock Porsche item or custom, and do you recommend this retrofit for all hi-performance 3.2SS builds?

I'm interested because....

While gathering researching for future re-build of SC engine as a 3.2SS I learned my 3.0 cylinders are not recommended for boring to 98mm because inadequate material thickness would exist at ID of original sealing ring, post-bore (I realize yours are original 98mm, not 3.0). One option suggested is to use a set of 3.2L cylinders and once bored/replated to 98mm they are compatible with SC heads and no sealing ring needed (not intuitive to me, but apparently same as original 3.2 Carrera).

Recognizing your build decisions are based on extensive knowledge and personal experience, any help correlating different opinions on this topic would be very helpful.

I just saw this at Supertec. She found a new home and is up and running.

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1 word Jim...SWEEEEEEEEEEEEEEEEEEET... WHAT AN ENGINE...!!!BEAUTIFUL...
CARE TO SHARE THE ENGINE SPECS & THE OIL SET UP YOU ARE RUNNING & ITS PLUMBING...?
THX FOR SHARING THE PICS & UPDATE...AS I AM SURE YOU KNOW, HENRY WILL TAKE CARE OF YOU...HE IS ONE OF THE STRAIGHT SHOOTER TYPE OF GUYS...! :-)

Hi Tweeks
I didn't mean to suggest that this beautiful project was mine. Henry asked me to take some pictures of a project he had finished and the pictures were still in my camera.
I think you can find all the specifications about this build at the a beginning of the thread.

Sorry for missing your question:
The copper ring was what I would label a creative attempt to reuse old racing parts. This engine was built for my own car which meant I wanted to be as frugal as possible and still build something special. I know, some of my choices don't look very frugal.
So, the cylinders I used were a set of low mileage but out of spec, flame ringed 98 mm Mahles.
Because I'm not a fan of flame rings on NA engines, I needed to deal with the groove. I searched the catalogs for a generic sealing ring with no success. Finally I decided to enlarge the groove and make a copper sealing ring to fit. The ring sits about .002" proud of the cylinder allowing for some crush.
As you might imagine, having the cylinders replated at Millennium, machining the grooves and fabricating the gaskets, we are now well over the cost of new cylinders. I believe our solution is a sealing enhancement but at the same time not a requirement. I may use thing process on future high performance turbo engines but who knows?


BTW: Thanks Jim for posting the pictures. I had plans to do it when I found some time.

Wow , thanks for the vote of confidence. What's that old saying? "you can fool some of the people some of the time"

The engine specs are indeed posted in the early part of the thread.

As for the coolers:
On early cars I hate seeing the cooler lines on the outside so we run flexible -12 line through the passenger side rocker, across the corner of the floor and out through the dope box.
On this car, because of the horse power being generated, the customer elected (wisely I might add) to employ a dual cooler system. We placed a 19 row Mocal cooler in the front of each wheel well. After that it is simply a matter of plumbing a thermostat and connecting the coolers. We plumbed the coolers to fill from the top to allow the oil to cascade down through the radiator cores (as opposed to filling from the bottom) but I'm not certain that natters.
The line is Aeroquip "Startlite" and the hose ends were chosen for their vintage aesthetics.
All the plumbing parts are available through BAT - MOCAL Oil Control Systems

thx guys for where the info is...
I say em as I see em... :-)
carry on all & sorry Jim that motor is not yours... :-)