Thoughts on some different engine configurations
 

Wayne’s book gives good rundown of some engine configurations that are known to work pretty well. I know it’s impossible to cover every unique configuration, but there are a few I’m interested in knowing about that are not documented in either Wayne or Andersons books. I wanted to list them here to see if I understand how/if they can be put together and to see if anyone has any thoughts about any of them.

Short stroke 2.5 – 90mm bore x 66mm stroke. Early aluminum case 2.0 with spigots bored out to accept 90mm P&Cs. Including all of the case upgrades it seems like a lot of machine work, but still a very neat engine.

Grady Clay's 2.8 – 92mm bore x 70.4mm stroke. 2.4E MFI motor with 92mm P&C upgrade.

Short stroke 2.8 – 95mm bore x 66mm stroke. Type 930/02 early turbo or euro carrera case and a early 66mm crank with 95mm P&Cs

Short stroke 3.0 – 98mm x 66mm stroke Type 930/02 early turbo or euro Carrera case and an early 66mm crank with 98mm P&Cs. I’ve never heard this mentioned here and I don’t even know if it’s even possible. Seems like it should work the same way a short stroke 2.8 would. Any thoughts or opinions on this one?

Short stroke 3.2 – 98mm bore x 70.4mm stroke. SC motor with ‘bolt on’ 98mm P&C upgrade. This one is in both Wayne and Bruce Andersons books and is known to be a great setup. (Could also be built on a 930/02 case if you need to use an older 2.7 crank with a 6 bolt flywheel)

Short stroke 3.3 – 100mm bore x 70.4mm stroke. SC motor with 100mm P&Cs. Some machine work needed, but sounds like a great engine. (Could also be built on a 930/02 case if you need to use an older 2.7 crank with a 6 bolt flywheel). Any thoughts or opinions?

rdanes 3.4 – 98mm bore x 74mm stroke. SC motor with a 3.2 Carrera crank and 98mm P&Cs. 98mm Mahles used are the 23mm wrist pin version for the Carrera.

3.4 Carrera – 98mm bore x 74mm stroke. 3.2 Carrera with ‘bolt on’ 98mm P&C upgrade.

3.5 – 100mm bore x 74mm stroke. 3.2 Carrera with the 100mm P&C upgrade. Some machine work needed.

Please add any other interesting engine configurations that you been able to make work, or correct me if any of these cannot or should not be attempted.

TIA

2.6 92mm bore X 66 mm stroke. good use for 2.8 RSR pistons. With the reduced stroke the compression ratio ( usually too high for 2.7 heads) is very usable.

3.1 100 mm bore 66mm stroke. This engine is built on a 3.0 turbo case with 100 cylinders. Revs high, huge power.

3.16 97 bore X 70.4 stroke. Quick revving engine config. for turbo aplication. Requires off set wrist pin in 3.0 rod or custom rods.

Thanks Henry! Thats exactly the type of stuff I was looking for.

Re: Thoughts on some different engine configurations
 

Short stroke 2.5 – 90mm bore x 66mm stroke. Early aluminum case 2.0 with spigots bored out to accept 90mm P&Cs. Including all of the case upgrades it seems like a lot of machine work, but still a very neat engine.

Basically a 2.7 engine with the smaller crank. You could make this engine by using the 66mm crank and rods with the rest of the engine being a 2.7. This would give you a higher-revving engine.

Grady Clay's 2.8 – 92mm bore x 70.4mm stroke. 2.4E MFI motor with 92mm P&C upgrade.

As Henry pointed out, these are the RSR-sized cylinders from 1972. These cylinders are hard to find and I don't know if anyone is making aftermarket ones.

Short stroke 2.8 – 95mm bore x 66mm stroke. Type 930/02 early turbo or euro carrera case and a early 66mm crank with 95mm P&Cs

A better solution than the first one (2.5) because the case has all of the upgrades already, and you can use standard components.

Short stroke 3.0 – 98mm x 66mm stroke Type 930/02 early turbo or euro Carrera case and an early 66mm crank with 98mm P&Cs. I’ve never heard this mentioned here and I don’t even know if it’s even possible. Seems like it should work the same way a short stroke 2.8 would. Any thoughts or opinions on this one?

Yes, it should work fine, providing you have the proper pistons - I'm sure JE could make you a set. This engine would have big barrels and a very small stroke. I don't know of anyone running this engine, but I would guess with a high-lift cam, it would be very difficult to drive on the street.

Short stroke 3.2 – 98mm bore x 70.4mm stroke. SC motor with ‘bolt on’ 98mm P&C upgrade. This one is in both Wayne and Bruce Andersons books and is known to be a great setup. (Could also be built on a 930/02 case if you need to use an older 2.7 crank with a 6 bolt flywheel)

My personal favorite. Higher-revving, higher-performance engine, but only if you use carbs or EFI and a high-lift, high profile cam. I wouldn't really bother if you're going to stick with CIS and the mild CIS cams.

Short stroke 3.3 – 100mm bore x 70.4mm stroke. SC motor with 100mm P&Cs. Some machine work needed, but sounds like a great engine. (Could also be built on a 930/02 case if you need to use an older 2.7 crank with a 6 bolt flywheel). Any thoughts or opinions?

Steve Weiner doesn't like 100mm - too thin. Not too many people run these sizes

rdanes 3.4 – 98mm bore x 74mm stroke. SC motor with a 3.2 Carrera crank and 98mm P&Cs. 98mm Mahles used are the 23mm wrist pin version for the Carrera.

This is essentially a 3.2 engine with a big bore kit bolted on. I would make sure that you run a good cam with this setup to extract the most out of it (also programmable EFI is really the only true way to go here.)

3.4 Carrera – 98mm bore x 74mm stroke. 3.2 Carrera with ‘bolt on’ 98mm P&C upgrade.

Exact same engine as above

3.5 – 100mm bore x 74mm stroke. 3.2 Carrera with the 100mm P&C upgrade. Some machine work needed.

Again, 100mm may be a bit too thin for reliable street use

Please add any other interesting engine configurations that you been able to make work, or correct me if any of these cannot or should not be attempted.

TIA

Important: Pistons, cylinders, cranks and rods, are only one part of the system here. A big bore engine with CIS and a mild cam seems to me like the equivalent of a 42" plasma screen with rabbit ears attached. You need to design the whole package as a unit in order to extract the most out of your engine dollars.

-Wayne

Some of the things to consider...
* Aside from the cylinder wall concerns with really Big Bore configuration, keep in mind that as the cylinder walls move away from the spark plug, it takes longer for the flame front to reach into the corners. This can cause all sorts of combustion and drivability issues.

* Mixing short strokes with really big bores can make it hard to achieve a high enough CR without making the piston crowns taller. If they get too tall, you wind up with the issues that the 2.0S and 906 pistons had.

The solution to both of these issues is to twin plug, but that means more money. You could get an engine with the same performance without twin plugging in many cases by making the stroke longer and the bore narrower as long as your piston speeds don't go over the top.

According to Frere and others, Porsche's engine design engineers were always concerned with the thermal efficiency of the motor. Having a larger bore then you need to keep the bottom end together increases the surface area of the combustion chamber which is apparently not a good thing because more heat is lost to the head and cylinder walls. I'm guessing that the results might include insufficient combustion, poor low speed running, insufficient cylinder filling, a low mpg number, and things like that. These things are especially challenges for hemi engines. The designers were also very concerned about the robustness of the design - which has always been a Porsche hallmark. For example they would routinely run dyno tests for extended periods of time to measure the drop-off in performance of an engine after breakin.

If you were talking about a modern 4 valve head with narrow valve angle, a compact combustion chamber, squash areas and flat topped pistons (as defined by the Cosworth DFV and copied by all of the modern multi-valve street engines), these same issues wouldn't exist.

Since all of the configurations that you described are based on the 911 engine, I doubt that any of them would be complete dogs, but I'm sure that with use over time, some of the more extreme variants will develop more issues compared a factory configuration. Using the 100 mm cylinders for example, they may work great to start, but as they wear and distort you will most likely find that the engine develops ring sealing problems which lead to excessive oil consumption, fouled plugs and a significant HP drop over the life of the engine.

Well said. In summary, the engine configurations that are most popular and most widely used, are often used for a reason - they are the best proven ones out there.

-Wayne

Great info, thanks guys.

I failed to mention that I was assuming twin plug on all of the engines I listed since they would all be relatively high compression. I will only be allowed to buy the reformulated gas that everyone loves so much here within the next month, so twinplug will most likely be a reality for me no matter what I end up putting in my car. I didnt want to think too hard about induction or cams until I was sure the longblock would bolt together.

I accept idea that the configurations that are documented are probably documented because they work well. The people that designed and built these cars were definitely on their toes. The factory setups are surprisingly hard to improve on.

Sleepless in Spec land
 

What is more likely true is that people build the safe, easy engine, not necessarily the best engine. A 911 engine is, for most, a huge undertaking and gambling on the unknown can cause many sleepless nights.
The engine I mentioned 97 x 70.4 is built for more than people tend to believe and yet you rarely hear about this configuration. I was skeptical, but visiting mechanic to my shop built one and the end result was amazing.
Also when built properly, the 100 mm engine will also offer tremendous results. We just built a 3.5 MFI single plug engine that amazed us on the Dyno. 369 RWHP @ 7660 rpm. http://forums.pelicanparts.com/uploa...1085491719.jpg

Henry, assuming 15% drivetrain loss that is 424hp from a 3.5.

Which is 121 hp per liter? Seems high for a normally aspirated engine. Many a 3.4 I have seen coming from Dawes Motorsports and other "tuners" that are twin plugged, ceramic coated high compression JEs, titanium valvtrain, etc ... only get 360hp +/- at the crank.

Dawe Motorsports 3.4L twin plugged.
http://www.dorkiphus.com/porsche/mod...win_plug_2.jpg

How'd you get there?

Jason

Hi Jason
I can't explain it. Our goal was 320 and we built the engine with that result in mind, so we were surprised with the result. At first we thought it was the dyno so we used a control vehicle, a 1972 CSL BMW that had plenty of dyno time on other dynos and the dyno actually seemed a little pessimistic on that car.
We don't usually quote HP because who wants that conflict. What I was saying in the post was that you can find hp in unusual places.

I agree with that entirely. I was just curious. To be honest, we rarely dyno our engines besides getting them set-up.

Lap times at the track and whether it is to be P1, P2, P3, .... are what matters to the driver :D

Cheers,

Jason

http://www.andial.com/

Andial has done more CIS/Motronic, big bore motors than anyone in the country I suspect. Lot of speculation on what will and won't work has been posted on the Max Moritz conversions on Pelican. Much of it has been incorrect. (appropraite wrist pin sizes, compression ratios and pistons styles come to mind)

I have to agree there are any number of great engine set ups available that don't typically get built. From my experience it is because either the owner or the builder is unaware of them or afraid of them.

The Andial Motronic 3.7 is a good example, as is my CIS 3.4. Mine will eat a new Boxster S (a good 3.2 Carerra isn't even in the game anymore) if last weekend is any example. Until you have built and driven some of the more esoteric combinations I would be very careful judging their worth.

Having been in two 3.6 conversions (varioram and the older 3.6) I can easily say I am happy with my end results on the CIS 3.4.

I am impressed with my 3.4 enough that the next project I am starting is a 3.8, Motronic, again with a mild cam like the 20/21 or something very similar. The big bores fit the way a majority of us drive on the street and give you plenty of thrills and power. Almost scary :)

Henry,
What else was done to the 3.5 to extract that much HP? Also interested in the torque#'s.
Thanks,
Mark

3.2 case, Carrera II oil pump
Mahle 100 mm Ps & Cs 10.8 to 1
3.3 turbo crank with 962 journals / 3.0 rods, titanium 935 rod bolts.
3.3 turbo heads ported & flowed by Supertec 41 mm in 38 mm ex. Aasco springs, ty retainers
1 and 7/8 header
Elgin cams 320 / 304 set @ 6.2
Recurved Dist by Supertec 36 degrees total advance 100 octane unleaded
Taylor wires, MSD ign box 7800 rev limit
Custom MFI 41 butterflies, stacks, custom MFI pump, Fuel lines and enrichment by Supertec
Dyno was a Dyno Jet @ Pecora Dyno Service, Costa Mesa
369 @ 7660
326@ 5300

It would most certainly be quite a bit better without the CIS, as that would allow you to run a more aggressive cam. CIS is just not a performance injection system. It's better suited for things like VW Jettas.

-Wayne

You certainly have a sense of humor Wayne. Bring your Ferrari or a Jetta along for a drive with us. My point is a more agressive cam is fine many places...like a track for example. On a street car, aggressive cams aren't all that practical. Fun, yes but practical..no.

CIS continues to get a bum rap no matter the evidence to the contrary. Perfect? No. Decent? You bet for a street car. We can continue to disagree but then I have both a 911 and a 3.4 Wayne, and you don't ;)

Any flat six 911 that gets 275 to 300 hp is pretty fun no matter what induction you have. You can do that with CIS or Motronic.

Thanks Henry. Congrats on that beast!

3.5......MFI.....drool

Henry, that is spectacular. There was obviously a lot of thought that went into designing and building that engine. I have to ask why you guys didnt twin plug it or run engine management instead of the MFI? I thought the twin plugs were bascially required on anything that size.

3.4.....MFI....twin plugs...drooling again

Jason, any more details on that monster?

and here is a couple of pretty quick ways to get a few extra HP ;)

for :369@ 7660 and 326@ 5300

Awesome engine! I want one ;)

I also. Hmmmm, a 400HP Duck.......

Yet another reminder that the need for twin plug conversions is highly overrated.

First of all, I have a 914-6 with a 3.2, and have written two books on Porsche 911s, so I would guess that I know what I'm talking about. Secondly, I'm building a short-stroke 3.2 with mod-S cams that I would never dream of putting CIS on. Third, there's plenty of "proof" that CIS is not a high performance system - heck it was never designed to be one.

Since you referenced the Ferrari, when they went to CIS, the HP dropped by about 20% due to the lack of performance of the CIS cams and system. That is why I specifically bought a carbureted version with independent throttle boddies. Likewise, the 911SC engine produces 180 HP, compared to the 210 of the MFI RS motor that proceeded it. This is even despite the low compression of the stock RS engine, and the increased displacement of the 3.0L.

Yes, you can increase displacement to overcome and overcompensate for any handicap with the CIS system. CIS is old technology (1970s), it doesn't perform pulsed metering, requires intake plenums and sensor plates that are affected by fuel reversion, and thus, you can only use relatively mild camshafts with them. Heck, the early CIS systems weren't even closed loop (exhaust gas sensor) systems.

As for an agressive cam in a 3.4 motor - it would be very driveable on the street, with gobs of low end torque. As I discuss in Chapter Four of my book, the increase in displacement eases the low-end torque problem that is common in motors like the early 'S' 2.0.

CIS is a good, reliable system that produces less emissions, and enables cars to pass smog tests. If building a big bore, high performance engine, it would not be at the top of my list. A fuel system that would supply individual throttle boddies would be first (TWM EFI, MFI, carbs). Then would come the closed-loop Motronic system with the common plenum. Then would be CIS.

Sorry to have offended you...

-Wayne

"First of all, I have a 914-6 with a 3.2, and have written two books on Porsche 911s, so I would guess that I know what I'm talking about"

You're kidding me right?

Ok, but I wasn't offended. Guess you missed the smiley face.

I never claimed that CIS was a performance induction, just a reliable one, made for passing emissions and cheap for those of us with CIS cars.

I could have used any induction I wanted. For now I wanted CIS for no other reason than to put CIS into perspective. I'll let the guys who drive my car make up their own minds.

There were so many changes beside the MFI (still one of the best induction sysetms available for HP) between '74 and '78 that your 210/180 comparison is moot.

More so when you do a little work on CIS (exhaust and cam which still make emissions) and get 215.

Dane

CIS CIS CIS, its great dont get me wrong, fires up in the morning without complaints, runs nicely throughout the day, emissions well those are decent i suspect. I have a 78 3.0 SC with the CIS and SSI's and also 20/21 cams. The engine makes very good power but I just cant wait to go wilder on the cams change to MFI and move up a little in displacement.

Hey wayne, I drive a jetta only because dad made the porsche his daily driver, I love hucking that thing around all the ricers here in pasadena, I just love the look on their faces.

quick question here. this summer my dad and i are rebuilding the engine with the max moritz kit but have decided on higher comp. pistons. as long as the engine is apart is it worth the extra money to throw in a 3.2 crank and rods to make it a 3.4??

I wouldn't get in a big hurry to up the compression past 9.8:1 as the Max Moritz pistons come. Eliminates the need for twin plug (if you are twin plugging I would go even larger MM style P&Cs) and there is more power than you might expect because of the improved piston design and combustion chamber @9:8:1.

Yes, the crank and rods are worth every penny and then some IMO. I'll have a dyno posted in the next few weeks to give you an idea of what is possible from CIS and a 3.4. The driving experience in unbelievable to this point.

Helmet Bott ran a 3.5 for many years in his personal car.

My response when asked is, "almost, scary fast" for my 3.4 CIS.
My mileage has gone up BTW and not down, even the harsh way I have been driving it on breakin.

Same set up I built to specifially. I wanted to pay for my engine in installements so the cams and SSIs came first. You can build a very inexpensive and extremely strong engine by adding a set of 98 P&Cs and the 3.2 crank to just what you have now while doing a valve job.

Hook up with Andial and beg a ride in one of their CIS big bore cars. That will answer a lot for you I suspect.

Hmm, I guess I did. Chalk it up to multiple nights of 5-hrs sleep.

Hmm, this I will respectfully disagree with. The 1975 Euro Carrera had the 2.7 engine, the 1976 Euro Carrera had the SC engine - each one year apart. The CIS motor replaced the RS motor in Europe.

- The two motors basically share the same crankshaft.
- The two cases are very similar, except that one is aluminum and one is magnesium (doesn't affect power).
- The pistons on the RS are shaped with higher domes to work with the 'S' camshaft. The 3.0 pistons are specifically shaped to work with the mild-profile CIS camshaft. Both engines had 8.5: compression
- The Euro Carrera was a 3.0L displacement, the RS engine was a 2.7 displacement
- The Euro Carrera had much bigger ports than the RS engine (39/35 vs. 36/35)
- They had the same sized valves

Looking at the specs for the Carrera 3.0, you'd think that the larger ports and larger displacement would generate an engine with significantly more power. Yet power per liter was down significantly from the previous year's system due to the switch to CIS and the mild CIS cam.

As I mentioned previously, the same thing happened to the Ferraris when they made a similar move to CIS - power was significantly down.

For an idea of what the 911SC could have been had it been sold with MFI, you have to look at the 911SCRS with 255 HP (although arguably, in a street car it would be lower, as you would want to drop the compression from 10.3:1 to about 9.8:1). A good individual throttle-body EFI system should be able to achieve at least that, if not more, using closed-loop monitoring of the mixture.

CIS is a very reliable, simple system that is good for emissions and everyday driving. I'm not knocking it - I'm simply saying that the other systems deliver better performance. I can't say for sure, but I would guess that the reason why Andial builds so many CIS big bore engines is so that they will pass smog. A friend of mine bought their experimental 3.7 CIS engine a few years ago (Steve Lee). I believe that car was left with the CIS system on it soley to avoid smog problems.

I suppose if I were going to spend a lot of money on a big bore upgrade, I would probably want to go with an EFI system to extract the maximum HP per dollar. However, if you're trying to keep the car smog legal, I can certainly see a very good argument for keeping and tweaking the existing CIS system.

-Wayne

Fair enough, how about this?

'74 2.7 MFI @ 210hp @ 6300k and 255@4500
'83 3.0 CIS @ 204hp @ 5900k and 267@4300

The 3.0 CIS SC ran at lower revs, with more torque, had a longer engine life by far, certainly was/is more reliable and passed some pretty strict emmissions.

Now add to that data a '78 or '79 with a good CIS cam and a set of SSIs makes 215hp no problem (with the same lower 8.5:1 compression), as many Pelicanites can atest. This while getting some of the best mileage seen in a 911 to date in '83. All things I really value in a street car.

I would hope any modern EFI system would better all of that. But at what cost? You have discouraged a 3.2 crank @ $1500 as too expensive, but figure a EFI @ $1500 plus labor is a good investment? No one is going to argue "there is no replacement for displacement" here, right?

CIS isn't the best performance induction available today or yesterday. We both agree on that. But from my many phone conversations with Pete and Deiter @ Andial, I was under the impression that they used CIS and Motronic for convenience, price and a nod to emissions, in that order. If CIS or Motronic were so limited I doubt they would have built as many performance engines with either induction.

Your points are well taken Wayne, I just don't agree with all your conclusions. But that is what makes a horse race, eh?

This is sortof a silly argument, because on some level, we're both agreeing with each other.

That's my whole point:

"convenience, price and a nod to emissions, in that order. "

Nowhere in that sentence is the word "performance", which was my original statement and point here.

Just to refresh:

I guess we're arguing over exactly what I meant by the word "better." In that sentence, I meant better as being "squeezing more horsepower out of the engine", not necessarily economical.

You did touch on a good point with the cost of an EFI system versus a 3.2 crankshaft. It's personal preference there. I would rather have an EFI system on a 3.2 than a CIS system on a 3.4 with a Carrera crank. In my opinion, the EFI system allows you a lot more freedom and flexibility, and also allows you to grow with the engine as you make changes. I'm a big fan of EFI...

-Wayne

Let me add another thing - my whole argument against CIS (and Motronic too) is that they are throttle-body induction systems. In order to run a more aggressive cam, you need to have individual throttle boddies, like on the MFI system or Weber carbs.

However, I'm not a huge fan of simply bolting carburetors onto a CIS engine. You will get poor gas mileage, an emissions nightmare, and decreased performance, overall. You may get a bit better throttle response, but it's at a high price. The only time I really advocate ditching the CIS system and bolting on carburetors is if you're going to swap out your camshafts.

-Wayne

Henry......For the 100mm cylinders are you boring the spigots on the case.......and if so how are you sealing tha case? "O-ringing" the spigot bores by cutting a groove in the bore perhaps?

Just saw that Henry was online and wanted to bump this to get some more input on his 3.5.

If I get into my 3.whateveritis and find the 100mm Mahles, I may spring for a 74mm crank and try something similar.

Also Henry, does your shop do the custom MFI setups?

Thanks Henry!

Yes, SUPERTEC builds custom MFI systems
 

Services offered by SUPERTEC
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(Restore early cases to original spigot size, or turn 7R case into 2.0 – 2.4 spigot size)

On this engine, the case was bored, in house and a special base gasket was made to seal it properly. On this engine as with all 911 /930 engines we build the cylinder base gasket was sealed with Ciril T.

Henry....

How about a group buy those 3.5 MFI engines! That sounds just incredible.... but im not sure my 901 could deal with it!

Terry:

We were told for YEARS that our 915s couldn't handle the 350+ hp we run through them. It has been 10+ years on multiple versions of twin-plugged 3.0L, 3.2L, 3.4L and 3.5L engines and the 915 box has NEVER been the problem.

Reading between the lines ... something else usually happens (race "rubbin", missed shifts, major and minor shunts, etc...) :D

Currently running 220+ hp through a 901 in a '68 2.0L ... no problems.

Jason

John (Otto) has run 901s with 300 horses through them for ages. I think he reinforces the center plate though...

-Wayne

Anyone have any thoughts on a short stroke 3.8 ? Using a 3.6 case modified to take 102mm pistons and a 3.2 crank which has a shorter stroke than the 3.6. The thinking is a higher reving version of a 3.8. I know special pistons would have to be made, but does anyone think it is worth it or should I just use a 3.6 crank ?

Shorter is better, at least that's what I tell my girlfriend.
 

I like any thinking that leans towards shorter stroke 911s. I think a better way to go would be to destroke and lighten (knife edge) the 3.6 crank. This would require a custom rod but it is my opinion that the 3.2 crank and rod combo sucks, and the 3.6 rod is too short. By destroking the 3.6 you get a smaller ( less friction) rod journal and larger radius at the flyweight for great stability ( more strength). By using the stock 3.6 wrist pin location in the 3.8 piston the rod gets longer and the engine gets happier. Why? Because the rod length to stroke ratio gets better ( less rod angularity = less piston side loading ). It is also my understanding that cylinder filling is improved when a piston spends more time at TDC and this time is lengthened by smaller rod angles.

Re: Shorter is better, at least that's what I tell my girlfriend.
 

First: love your subject line!

Henry, I have a specific question I'd like your opinion on, and that of anyone else interested:

3.0s can be built relatively easily in a couple of different configurations:

1. 70.4x95 (SC, 3.0 Carrera, 3.0RS, 3.0RSR)

2. 66x98 (bigger bore version of short stroke 2.8)

Note that the 3.0RSR made peak power at 8000rpm, with max. engine speed slightly above that. I don't think the factory was using any 98mm cylinders at the time, so #2 might not have been obvious.

Here's my question: If you built a #2 configuration race engine, what power peak RPM (or torque peak, whatever you prefer) would you be shooting for? would you try to use bigger cams to lift the power peak over 8000 rpm, perhaps 8500?

My point is, if the power peak is not any higher than 8000 or so as in the RSR, at least in a 3.0 it would probably make sense to use the #1 configuration, not least because it is much easier to create. I make no statements about the 3.2/3.6 since they have quite a longer stroke.

However, even longer stroke 911 engines are still very oversquare compared to many production engines. As an example, the original honda S2000 engine has an 84mm stroke, and a 9000 redline. No doubt the reciprocating assemblies are lighter (have you seen a honda rod lately), but I'm curious where the balance point is in 911 engines between stroke and comfortable RPM.

TIA