Biblio-Porsche: Engine - 3.0 CIS Rebuild vs. 3.2 Carrera Swap


From: "Volney Spalding" 
Date: Tue, 10 Dec 1996 10:21:07 -0800
To: porschefans-911@ioio.com
Subject: Re: Engine rebuild on '80 911SC

Pfans:

>>Boy do I feel stupid.  There is a really fine 3.2 upgrade for a 3.0, called
>the Max Moritz upgrade.  ALL you do is put different pistons and cylinders
>on, then richen the mixture a bit, and you have a 3.2 sitting under the
>original 3.0 CIS system.  Although I have only done one of them, it really
>is that easy.  Any other route to a 3.2 would have your shop charging you
>for a lot of extra work.
>

To add my .02:

I have a 79 3.0 with the 3.2 upgrade in my 71 coupe.
It has 20k miles since the rebuild so I can't really speak for
durability, but it has no driveability problems and looks
like a stock 3.0.

If I had an SC and I had a good mechanic I would get the 3.2 upgrade
rather than a DME motor since it would look completely stock and there
would be no need (depending on what state you live in) to recertify
the car to the year of the engine.  This alone (at least in CA) is a
big reason and saves all the rewiring necessary to go to DME.

OTOH, a good, used, unrebuilt 3.0 or 3.2 might be a safer bet reliability-
wise than a rebuilt 3.x except that with a rebuild you can get a warranty.
Rebuilt engines fail more often (according to some) than a stock
low-mileage engine swap.  Either way, get a good mechanic to do the
rebuild or buy a used engine with a known history and you should be
fine.  You'd be surprised how many used engines have had their
serial numbers ground off and no one can tell you anything about where
they came from.... :(

As it happens, I just asked Bruce A. what kind of power increase you can
expect from this conversion: (Bruce, hope you don't mind)

> Hi Volney,
>
> Figure that the power increase will be a little less than the percentage
> displacement increase. The SC is 2994 cc and with the 98 mm pistons it will
> be 3186 cc which is a 6.4 % increase. So if you figure that the engine made
> 180 hp you will have 191.5 hp, if you are optimistic and assume that your
> engine had 204 hp you will have 217 hp. With the correct muffler you will get
> a 13 to 15 hp increase from the SSI heat exchangers and a dual outlet sport
> type muffler. So you will have somewhere in between 204.5 hp and 232 hp. But
> the only way you will ever know for sure is run the engine on a dyno.
>
> Bruce Anderson


--
Volney Spalding			     			
Silicon Graphics Computer Systems
vol@espresso.corp.sgi.com
415.933.2879

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Date: Tue, 10 Dec 1996 21:51:29 -0700
From: Dennis Kalma 
To: Volney Spalding 
Subject: Re: Engine rebuild on '80 911SC

What I have been told will confirm the numbers that Bruce gave....Kremer
folks figured that the "stock" 3.2 upgrade (eg no other changes) would
give around 220hp, add SSI's to get to maybe 230 and then they said
maybe another 5 hp or so for the "tuning" they did (mainly a good intake
manifold polish, and I suspect a bit of port matching) as well as some
stuff in the case to reduce windage....
This was working off of the 9.8:1 compression and in fairly rich tune..

I tell people mine is around 230hp on a bad day and 235 on a  good
day....

Dennis

1975 911S with Kremer 3.2



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Date: Wed, 11 Dec 1996 00:35:19 -0500
To: PorscheFans-911@ioio.com
From: Gary Griffiths 
Subject: Re: Engine rebuild on '80 911SC

        With all the discussion on the positives and negatives of 3.0's and
3.2's does anyone completely understand the reduction in rod bolt size for
models following the 3.0. I presume it was done to reduce reciprocating weight.

        I believe the 3.0 had 10mm bolts and the 3.2 & 3.6 dropped to 9mm
rod bolts. I have seen failures on 3 occasions where it appears that the
bolts stretch and the bearing spins. This has happened on cars that were
driven hard in autocross or driving events. I haven't seen it in 3.0L.
engines to date. Is there another explanation such as a lubrication problem
or has this change in bolt size weakened the engine?

        Gary


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Date: Wed, 11 Dec 1996 07:41:27 -0500
From: Randy Hubbard 
To: PorscheFans-911@ioio.com
Subject: Re: Engine rebuild on '80 911SC

Gary Griffiths wrote:
>
>         With all the discussion on the positives and negatives of 3.0's and
> 3.2's does anyone completely understand the reduction in rod bolt size for
> models following the 3.0. I presume it was done to reduce reciprocating weight.
>
>         I believe the 3.0 had 10mm bolts and the 3.2 & 3.6 dropped to 9mm
> rod bolts. I have seen failures on 3 occasions where it appears that the
> bolts stretch and the bearing spins. This has happened on cars that were
> driven hard in autocross or driving events. I haven't seen it in 3.0L.
> engines to date. Is there another explanation such as a lubrication problem
> or has this change in bolt size weakened the engine?
>
>         Gary
>
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Hi Gary,

The 9mm bolt will definitely fatigue and stretch when the engines are
run hard. The 3.2L & 3.6L engines have a higher "jerk moment" at TDC
when the piston changes direction, due to the longer stroke and heavier
piston mass. This places a major increase in load on a bolt that has
been reduced in size. You have seen the results, as have many others...

As a long time Porsche guy, PCA member, and engine designer, I'll risk a
slightly commercial message and advise you take a look at our Website
for useful info. on this subject.

If you have any other questions, I'll be glad to answer them.

Regards,

On the 'Bahn,

Randy, a.k.a. BoltMeister

NEW** VW/Porsche/BMW Interest At: http://www.wwnet.com/~raceware **NEW

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Date: Wed, 11 Dec 1996 20:56:00 -0700
From: Dennis Kalma 
To: Scott Winders 
Subject: Re: Engine rebuild on '80 911SC

Sorry, base for my engine was the 204 hp european engine...not the 180
hp North American engine. Increases calculate from there.

I also think that the Kremer's were a little pessimistic in their
assessment, the crankcase mods to improve air flow are worth about 10 hp
(according to Bruce A's book), the fuel injection mods, bit of polishing
and port/gasket matching is probably worth a few as well....Kremer's
said to add about 5 in total.....

Dennis

'75 911S with Kremer 3.2



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Date: Wed, 11 Dec 1996 14:38:05 -0500
From: Race911@aol.com
To: PorscheFans-911@ioio.com
Subject: Another way to do 3.2L

To add more on the 3.0 to 3.2 discussion:

I've also done about 10 3.2L CIS engines by just changing out the
crank/rods/p&c set from a motronic engine (74.4 X 95).  Seems to work fine;
I've had 3 different variants in my race car.  The problem these days is
obtaining low mileage Mahle Nicasil p&c sets.  Used to be able to get them
quite freely (and cheaply) from the guys doing 3.4L upgrades.  Now you kind
of have to find them.   Figure that the cost of all the used components is
about half that of the Mahle 98mm set.  And when you're done you have a 3.0
crank for your display case! ( Anyone need good 3.0 cranks.......cheap?)
 Caveat:  most '87 3.2 engines had KS Alusil p&c sets, which probably should
be avoided unless Mahles can't be found.

Of course, it's always better to use large port CIS (i.e. 78-79 US or any
year Euro) and an early exhaust.  A couple of the ones I've done were "smog
engines" just reaping the benefit of the displacement increase; they worked
out fine for their intended use.  3.6L cams also help out.

Ken Shahoian

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Last Update: 28-Mar-1997 11:53 AM