Quick FAQ 3.0/3.2 upgrades to 3.2/3.4

[Wayne 962]

Quick FAQ 3.0/3.2 upgrades to 3.2/3.4

Hi folks. There has been lots of confusion on this topic as of late. Although this information is included and well documented in my Engine Book (http://www.101projects.com), it's not always easy to find in there, or it's hidden away with some other information. Here are some facts on the late model (1976-89) 3.0/3.2/3.3 engines:

You cannot use stock Porsche 3.2 Pistons on a stock 3.0 engine.
This is the most common misconception around. The stroke of the 3.2 engine is longer than the stroke of the 3.0 engine. To maintain the same deck height across the two engines (and all Porsche engines), the hole for the piston pin is in a different location on the 3.2 than on the 3.0. So, if you find a stock 3.2 Piston and Cylinder kit for cheap, you cannot use the pistons on your 3.0 to increase the displacement. Technically, you can make this combination work, but because the piston pin is offset farther into the piston, the deck height will be way off, you won't increase your displacement, and you will have very low compression, and a very doggy engine. In addition, the wrist pins on the 3.2 and 3.3 are 1mm larger than the 3.0 (22mm vs. 23mm), so technically, you couldn't mate the 3.2 pistons to the 3.0 rods even if you wanted to. I have heard of people enlarging piston pin bushings, but again, this would cause unnecessary complexity.

You CAN use and interchange 3.0 and 3.2 cylinders
The stock 3.0 and stock 3.2 piston and cylinder kits all use the same 95mm cylinders. Assuming that you keep Nikasil and Alusil pistons and cylinders together, you can swap cylinders from the 3.0 and the 3.2. Remember not to mix Alusil pistons with Nikasil cylinders, and/or Alusil cylinders with Nikasil pistons. See the engine book for more details on this. Bottomline - the 3.0 and 3.2 cylinders are the same diameter, and height and are interchangeable. On caveat - the 3.0 cylinders use a CE-type head gasket between the cylinder and the head - the 3.2 cylinders do not have this gasket. There are workarounds for this, but it adds another element of complexity if you're mixing and matching cylinders.

To upgrade a stock 3.0 Engine to a 3.2, you need a special "Big Bore" kit.
This kit turns your 3.0 into what is known as a short-stroke 3.2. The stroke remains the same at 70.4mm because you're not swapping out the crankshaft. Instead, you are installing what are known as "Big Bore" pistons and cylinders which are 98mm wide (as opposed to the normal 95mm for the 3.0). These are special pistons and cylinders that were never a factory kit available from Porsche (as far as I know). There is no Porsche part number for these - they are an aftermarket kit available from Mahle. These are also sometimes known as the Max-Moritz kit. They are available in various compression ratios - I have a set that is 10.5 and resembles the original RSR setup in design. These sets are "plug-n-play" and do not require modifications to your case or heads. The piston pin offset in these kits is specifically made to work with the 3.0 crankshaft, and these will not work with the 3.2.

To upgrade a stock 3.2 Engine to a 3.4, you need a special "Big Bore" kit.
Basically the same as above, except that the kit is a 3.4 "big bore" kit specially made for the 3.2 engines. Like the kits mentioned above, these are also 98mm (they use the same cylinders), but the pistons have their piston pin location drilled specifically to accomodate the longer crankshaft (74.4mm). I don't think that this was ever a factory kit either, and as such, I have never seen a Porsche part number associated with these kits.

European Carrera 3.0 Upgrades
The Euro Carrera can be looked at as being the same as the 911SC 3.0L engine for the purpose of upgrading. In reality, the Euro Carrera actually uses the 70.4mm crankshaft from the 2.4/2.7 engines, enabling a wide variety of engine designs. You can run an early 66mm crankshaft with a big bore kit (3.0 or 3.2) and make a very high-revving, short-stroke engine (this is a popular 2.5 combination). The Euro Carrera and the 1976-77 911 Turbo share the same engine case.

911 Turbo Upgrades
If you are running a turbo on your Turbo engine, then you must stick with the standard big bore kits that are specifically made for the Turbo. These are low-compression pistons and cylinders that are specifically engineered to handle the high boost compressions at higher throttle. If you are using a Turbo long block, and turning it into a normally aspirated engine (NA), then the same rules that apply to the 3.0/3.2 apply to the Turbo longblock (3.0/3.3). The 3.0 Turbo longblock is nearly identical to the Euro Carrera & 911SC, and the Turbo 3.3 longblock is nearly identical to the Carrera 3.2 engine.

We are going to be redesigning the Engine Rebuild Wizard (http://www.pelicanparts.com/cgi-bin/wizards/parts_wizard.cgi?wizard_root=911_engine_rebuild) in the very near future to incorporate some new features. With the manufactured of L&N Engineering's Nickies and JE pistons, you will be able to mix and match any piston / cylinder combination you choose, and actually dial in your compression ratio exactly where you want it. We will be offering some combinations that are custom designed by us (available only through Pelican), and will be *guaranteed* to work (no guesswork or head scratching). Coming very soon will be a multitude of kits that will allow you to upgrade your 3.0 to 3.2 or greater or your 3.2 to 3.4 or greater, with your chosen compression ratio. This will allow you to tailor your engine for your climate, gas octane availability, and driving habits.

-Wayne

[Wayne 962]

P.S. Dave at TRE reminded me of two important facts too that I left out of the above paragraphs. Thanks Dave!

-Wayne

[rdane]

Great post Wayne. I think it was needed for some time. Thank you.

I think Ed is right. When it comes time to think about a 3.2 built on a 3.0 you need to know the options of what it takes to make the 3.4 on the 3.0. Crank and rods are not that expensive in the grand scheme of a rebuild. The rest of the conversion is minor. (I hope

Have you done your's Ed?

[Wayne 962]

Six or 1/2 dozen - it doesn't matter. The 3.0 and 3.2 cases are almost identical, so changing out the crank and rods - you're basically swaping the guts of a 3.2 into a 3.0.

I disagree though on the availability of the 3.2 crank and rods - I have found these difficult to find...

-Wayne

[smdubovsky]

If you use the 101/2mm cyls you can make a 3.4(+) w/ the SC crank. Since people are getting good at nikasil plating now, you could bore the 100mm cyls to 101.1 & get some J&E's for a short stroke 3.4? No? I think I've even seen 101.1s for sale somewhere but can't find them right now (might have been from American Air Cooled cylinders?)

Also, the distance from the wrist pin to the flat part of the piston (the edge for most 911s) is called "compression height". It is shorter on the 3.2 and 3.6 pistons which is why they can't be interchanged w/ the earlier ones.

I was told by several reputable builders that when rebushing the small end of SC rods, there is more than enough meat to bore up to the larger wrist pin if needed. It was also mentioned that you can easily bore the hole off center to make the rod slightly longer/shorter to adjust compression & deck height on an existing P&C set.

SMD
Who is running 100mm P&Cs in his SC (3.32L)

[rdane]

SMD have you dynoed your car? Mind sharing the specs of the rebuild?

[MotoSook]

SMD, was your case machined to open it up for that application?

[dd74]

I saw a 3.2 crank recently for $1.5K. So what Ed says does have validation. But its condition is one thing I'd worry about. Is there such a thing as a "bad crank." How can one tell?

As far as 100mm p/cs, I think you're going to get into some fairly heavy machining, grinding down the spigots in general, to fit those in a 3.0. I might be wrong, but that's what I recall.

[smdubovsky]

Yes, the 100mm+ cyls need the case spigots machined. Easy w/ a mill, but you need to take the case studs out.

I don't want to hijack the thread but quickly:
I haven't dynoed yet (too cold and just got the motor rebuilt (tnx to Waynes excellent book!)) 83 SC case, 100mm P&C (=3.32L), 10.7:1 J&Es w/ total seal rings, boat tailed case, 993 case studs, ARP rod bolts, twin plug 3.2 heads (heavily ported to ~40 to 42mm), EBS springs and Ti retainers, 1-3/4" bursch headers, 44mm TWM throttles, Haltech E11 ecu, 993 engine filter adapter, 964 "cup" flywheel (for 60-2 ecu trigger), Al pressure plate, and 964 cams. Its heavily undercammed but I need to pass emissions for the next ~2yrs (which it did). Its a hoot driving around the block I got the cyls, heads, and TWMs really cheap so they aren't all "ideal" fits. HP goal was 270-ish at the crank.

SMD
83 911SC platinum --> 74 blue 3.0RSR/IROC clone

[Jeremy Cottrell]

Wayne, what are the facts that Dave mentioned??

[rdane]

I disagree though on the availability of the 3.2 crank and rods - I have found these difficult to find...

-Wayne

Just to add some info to the thread. After calling Pelican, I found my new Pauter rods and 3.2 crank in mid Nov. '03 with a few minutes on the phone. Crank was magnafluxed and like new.

Because of Wayne's comment I was considering myself lucky. But I don't think that is the case. I just made a similar phone call (2/13/04) and found another 3.2/3.3 crank is perfect condition that has been magnafluxed.

Costs vary from 1300 to 1700 for a used crank at retail.

[Wayne 962]

Originally posted by Wayne at Pelican Parts
I disagree though on the availability of the 3.2 crank and rods - I have found these difficult to find...

-Wayne

At reasonable prices. A crank and rods for $2300 is a bit expensive, in my opinion.

-Wayne

[rdane]

Originally posted by Wayne at Pelican Parts
Instead, you are installing what are known as "Big Bore" pistons and cylinders which are 98mm wide (as opposed to the normal 95mm for the 3.0). These are special pistons and cylinders that were never a factory kit available from Porsche (as far as I know). There is no Porsche part number for these - they are an aftermarket kit available from Mahle. These are also sometimes known as the Max-Moritz kit. They are available in various compression ratios - I have a set that is 10.5 and resembles the original RSR setup in design. These sets are "plug-n-play" and do not require modifications to your case or heads. The piston pin offset in these kits is specifically made to work with the 3.0 crankshaft, and these will not work with the 3.2.

Couple of questions and comments. If anyone can varify or rebut the information I have picked up and posting I would be grateful. Might make it easier to sort all this out if anyone cares to add more info.

My understanding is there are at least 10 different 98mm piston and cylinder sets for the 911 from Mahle. The only set that was considered a Max Moritz set was a 3.2 upgrade (3186cc) for the CIS 3.0 with a 70.4 crank. The piston crown profile was wedged shaped and offered a better combustion chamber and burn front specifically for the CIS system. The piston design was intended to be a "plug and play" big bore with single plugs and a stated compression of 9.3:1.

The other P&C set that often gets credit (correctly I believe) as a Max Moritz design is a 3.4 conversion on the 3.2. (actually a 3367cc which would be better called a 3.35 Liter instead of a 3.4 The wrist pins were changed to 23mm (from 22mm) for use with the 74.4 crank but have the same 98mm bore size and more importantly, the CIS/Motronic compatible, wedge shaped dome. The compression ratio was changed to 9.8:1. That ratio split the difference between the ROW 3.2 Carrera @ 10.3:1 and the USA compression @ 9.5:1. More importantly, again, the set was designed for CIS or Motronic, the mild cam they require, single plugs and 93 octane premium gas.

These are all important issues when pricing a rebuild.

You are looking at a straight 6.4% or 12% power gain in a 98mm P&C set alone, depending on application and crank.

I have been told that either the SC or the later 3.2 Carrera could be ordered from Porsche Germany with this upgrade. Or after purchase in Germany the car could be taken directly to Werk1, as Bruce Anderson mentioned in "Porsche 911 Performance Handbook" and have the P&Cs change. Richen up the mixture a bit and you are good to go. I have also read but can't find the comments about some of the Porsche management driving either a Max Moritz 3.0 to 3.2 or a 3.2 to 3.4 conversion/upgrade on their personal car. I'll have to find that one again.

Just to confuse the issue RUF offered a set of 98mm P&Cs for the 3.2 Carrera through Mahle also. But I don't know the piston design or the compression ratio. I wonder if they are still availabe from Mahle or RUF?

Porsche made a racing pistons for the SC which were 95mm and Carrera 98mm which were very close in design to the original Max Moritz 98mm pistons. The big difference from what I have gathered is they are 10.3:1 compression and designed for a twin plug car and wild cams. Easy enough to tell the difference by the deeper valve relief cuts in the Porsche racing pistons.

I have a set that is 10.5 and resembles the original RSR setup in design

Wayne, is this a a 98 mm set @ 10.5? I know Mahle makes a 95 mm set @ 10.3:1 for the RSR and a 70.4 mm crank. The similar 98mm set has 23mm wrist pins. Any chance of seeing a picture of your pistons. I'll get a shot of mine for the 3.2 to 3.4 Motoronic and post is asap.

Most of my machine work is done and the bottom should start going back together next week. I'll post more as I go on my 3.0 going to a 3.35

Additional comments anyone?

[Wayne 962]

Originally posted by rdane
Wayne, is this a a 98 mm set @ 10.5? I know Mahle makes a 98 mm set @ 10.3:1 for the RSR. Any chance of seeing a picture of your pistons. I'll get a shot of mine for the 3.2 to 3.4 Motoronic and post is asap.

It's probably the 10.3 one, 10.5 is the number I remember in my head (not written down). It very well might be the 10.3 ones...

-Wayne

[emcon5]

Any chance of seeing a picture of your pistons. I'll get a shot of mine for the 3.2 to 3.4 Motoronic and post is asap.

You can see a picture of mine here:
Actual compression with 3.4 max moritz?

I remember 10.5:1 as well, but I could be mistaken. I looked on the box, and it didn't say. They have 22mm wrist pins.

Tom

[rdane]

Borrowed your photo Tom, hope that is OK.

My Mahle list says the only 98mm set with 22mm wrist pins for a 70.4mm crank is a 10.3:1 for the RSR. Similar list on page 170 of Anderson's book.

The Max Moritz pistons shown on page of 147 in Anderson's book are 3.2 98s and the relief cuts are not as deep as the what is shown in this picture. Certainly could be the difference between 9.8 and 10.3 in compression.

My point was there are indeed Porsche factory racing pistons with the wedge shaped dome and require twin plugs. (page 148, Anderson again from Porsche AG, SC racing pistons) The "Max Moritz" converstions were originally designed to be "plug and play", single plug, conversion.

Not that Max Moritz couldn't have designed more pistons. His was/is a race shop afterall.

When I bought my 98 mm Mahle set last month I had the option of 10.3:1, 9.8:1 or 9.3:1 depending on wrist pins and piston shape. There are specific Mahle 98 pistons for each of the following; Motronic/CIS, mechnical injection, RUF's spec and "racing" which I would assume has pistons cuts for a fairly wild cam. I'll get a comparison picture of my 9.8:1, 98s when I get a chance to drop by the shop this week.

[emcon5]

Originally posted by rdane
The Max Moritz pistons shown on page of 147 in Anderson's book are 3.2 98s and the relief cuts are not as deep as the what is shown in this picture.

The valve pockets in that set of pistons have been machined deeper to work with a hot cam. I should have made that more clear in the other post. I believe the pictured piston started life as 9.3:1, but are lower with the deep pockets.

I also mentioned in the other thread that the 10.3 Mahle set is with RSR heads, which have a smaller combutsion chamber. In a SC 90cc head, they are ~9.8:1.

The more I think about it, I think you are right, and they are 10.3:1, not 10.5.

Tom

[Wayne 962]

Mine look just like everyone else's:



-Wayne

[rdane]

Mine look just like everyone else's

If that is what they look like then I supect we are looking at the Porsche AG 98.mm RSR racing pistons for a hot cam and twin plugs. Not a Max Moritz, big bore conversion for CIS or Motronic.

The Mahle Max Moritz pistons are only a wedge shape design and specifically for the CIS and Motronic injection at 9.8:1 or 10.3. (twin plugs would then be dependent on octane available to you)

Here is the current Mahle list afaik

3.0L
98mm Street 1978-1983 3.2L 9.8:1 (Max Moritz wedge design)
98mm Race 3.2 10.5:1 from 3.0L RSR (traditional dome)

3.2 L
Carrera 74.4 1984-1989
98mm Street 3.4L 9.8:1
mechanical inj / carb

98mm Race 3.4L 10.5:1 (Mahle/Porsche AG pistons shown I *think*)



98mm Street (both Max Moritz wedge designs)
3.4L 9.8:1 motronic
3.4L 10.3:1 motronic

My only concern here is that there is a weath of misinformation out on the 3.2 and 3.4 conversions done with the Mahle Max Moritz pistons. They are designed specifically for CIS and Motronic and single plug applications. High octane gas (93 and better in most locations) or twin plugs would be suggested for the Max Moritz 10.3:1 set.

The valve pockets in that set of pistons (9.8:1, 98mm Max Moritz) have been machined deeper to work with a hot cam.

Tom you had me digging for more references on those pistons Thanks for clearing that up!

I also found the referenec to the big bore cars used by the factory. It was Helmet Bott that used a big bore conversion in his personal car for many years. But not the 98s as I had remembered. They were 100mm for a 3.5! Interesting details in Frere's book page 80/81.

[MotoSook]

rdane: Why couldn't you use the MM 9.8:1 CR pistons with dual plugs? I realize Max Moritz and other big bore conversion companies initially did it on Motronic or CIS cars with single plug, but what would be the draw back to a 9.8:1 CR 98mm dual plug engine?