making a 3.0 engine into a 3.2

[Kraftwerk]

What are the pro's and cons? Seems like it would be easier just to swap? There are few 'BUILT' 3.2 's out there made from 3.0 cases. Is that a "while-you-are-in-there" thing, pushed to extreme proportions?

[jsmithcds]

The pro's are a quick reving hot little motor with a good bit of snap above 4k. The con is the $10k(roughly) cost if you don't do it yourself. I did it when my motor had to be rebuilt anyway. Not worth the price if your motor is in good shape currently. If it has to be rebuilt anyway it is a while you are in there upgrade. If you have some extra cash laying around it is a fun motor. Do a search on 3.2l SS you will find several post on it. Your 83 would have to have the heads ported as well. The 78 and 79 are already larger as in my case.

Justin

[longhornchris04]

Not sure all the pros/cons, but I can explain why its common...

Something like 50% of the 3.0Ls used Alusil cylinders which can't reliably be re-ringed... so if you're rebuilding one then odds are you have to replace the cylinders... which necessitates replacing the pistons as well.

The catch is that the 98mm P&Cs are only marginally more expensive (sometimes cheaper) than the 95mm P&Cs... so if you are rebuilding then engine and have to replace the cylinders, going to a 3.2 short stroke is basically free.

From an engine geometry perspective, this is a short stroke engine, with a larger bore than 'normal' as compared to the stock 3.2, which uses a different crank shaft and the 95mm P&Cs. If you do the same P&C swap on a 3.2L, you get a 3.4SS.

The catch here is that you aren't changing the other components (induction, heads, exhaust) so you don't get the same engine as the stock 3.2 which uses Mototronic, has different heads (port size), etc.

Now, the other major benefit to this as compared to just an engine swap is that adding 2mm to the piston bores doesn't change the external dimensions of the engine in the slightest, nor does it change any of its interfaces. Thus, it should go right back into place... and if you are in a pollution control state (like California) its completely invisible to CARB, provided the rest of the emissions equipment is working.

[Kraftwerk]

Thanks for the good information.

[SP2]

Bruce Anderson's book says owners in Germany would pick up their brand new SC's, then take them right over to Werk I to have the 3.2 p/c's put in.

[kenikh]

If you need new P/Cs, 98mm is the way to go. Bore the 95s cyls, recoat w/ Nikasil (works fine on alusil) buy some used Mahle or JE pistons and off you go. With JEs, you get a nice option of bying just pistons and easily bump compression to Euro spec, too. New Mahles require buying cyls.

Swapping in a 3.2 crank is not the way to go...bad rods, bad rod ratio.

[Scott R]

98M's and JE pistons were the same cost as 95's when I did mine. These were Nikies from our host here. I really enjoy the extra displacement on my SC.

[kenikh]

There really is no better cylinder than a Nickie. Not cheap, but JEs and Nickies are very compelling given the cost of Mahles.

[D911SC]

Originally Posted by kenikh

If you need new P/Cs, 98mm is the way to go. Bore the 95s cyls, recoat w/ Nikasil (works fine on alusil) buy some used Mahle or JE pistons and off you go. With JEs, you get a nice option of bying just pistons and easily bump compression to Euro spec, too. New Mahles require buying cyls.

Swapping in a 3.2 crank is not the way to go...bad rods, bad rod ratio.

I didn't realise you could bore the 95's out to 98. Can you confirm this?

What does it cost to bore and recoat in comparison to buying 98mm Nickies?

[D911SC]

Originally Posted by Kraftwerk

What are the pro's and cons? Seems like it would be easier just to swap? There are few 'BUILT' 3.2 's out there made from 3.0 cases. Is that a "while-you-are-in-there" thing, pushed to extreme proportions?

Lots of threads here and a mountain of info to help you make your decision.

Have a look at these ones, although there is discussion of lots more mods than just P&C's.

Wayne's book is also an excellent source of info.

3.0 SC HP Expectation - post modification

Shanes 3.2 SS - Recommendations and Advice

[haycait911]

Originally Posted by kenikh

Swapping in a 3.2 crank is not the way to go...bad rods, bad rod ratio.

why? what do you mean?

[pete917]

what sort of power does this make out of interest

[kenikh]

Originally Posted by haycait911

why? what do you mean?

Longer stroke & shorter rods = more side loading of pistons.

The bigget issue is the rods themselves. They are fine stock, but are very weak. Pretty much any 3.2 performance build requires rods as a result.

Thus, pistons are a better solution.

[911st]

Couple of things.

I do not think you can bore the SC cylinder because of the head sealing ring grove. I think you have to find a set of used 3.2 cylinders.

Power from a 3.2 conversion is a double whammy. You great about 6% more power from the extra displacement plus over a 8.5/1 you get about another 3-5% bump from compression.

If one wants to go with a twin plug and bump compression another point there is a about 2-3% more power from the TP's and another 3% from the compression.

Through carb's, headers, and even cams and we are looking at not only a nice bump in power but one sweet running motor.

The stock 3.0 rods are good, the 3.2 Carrera rods have smaller rod bolts and a weakness. Add to that lighter weight J&E pistons and wrist pins and one can build a motor that can probably be run up into the mid 7000's without issue.

But as noted, it would probably be more economic and make for a faster car to just sell off a 3.0 and fit a good used 3.6.

Still, there are some Porsche motor combonations that are fun. A 2.2-2.6 with a 66mm crank, a 2.8 twin plug, and a 3.2ss can be a bit more than the sum of there parts.

[Steve@Rennsport]

Some thoughts on this based on experience,....

1) We've done quite a few of these over the years and its a very nice upgrade, IF its done properly. With a good exhaust, its quite noticable,...

2) SC cylinders should not be bored as there isn't sufficient material between the bore and the sealing ring grooves for reliability. I've seen too many failures so one should use either Mahle P/C's or maybe some Nickie/JE's.

3) Twin ignition is NOT necessary if one uses the Mahle wedge-dome P/C's made expressly for this application. One gets a decent CR that will run nicely on pump gas.

4) Stock rods w/ARP bolts are plenty good when used with stock or 964 cams. For operation at 7K and above, one needs aftermarket rods, bearings, and some oiling mods. Its not an issue with CIS engines,....

We recently did such a 3.2 (based on an early SC) with PMO's and mod-S cams. and it made over 260BHP with SSI's and OEM early muffler. It was 270+ with a better muffler,...

[SP2]

Hi Steve, what is a better muffler?

[Steve@Rennsport]

Originally Posted by SP2

Hi Steve, what is a better muffler?

LOL,..that depends on the engine, its configuration and RPM range, and what kind of noise levels one expects.

As you can see, in many cases, its not a "one-size-fits-all" solution.

[Scott R]

Originally Posted by Steve@Rennsport

Some thoughts on this based on experience,....

1) We've done quite a few of these over the years and its a very nice upgrade, IF its done properly. With a good exhaust, its quite noticable,...

2) SC cylinders should not be bored as there isn't sufficient material between the bore and the sealing ring grooves for reliability. I've seen too many failures so one should use either Mahle P/C's or maybe some Nickie/JE's.

3) Twin ignition is NOT necessary if one uses the Mahle wedge-dome P/C's made expressly for this application. One gets a decent CR that will run nicely on pump gas.

4) Stock rods w/ARP bolts are plenty good when used with stock or 964 cams. For operation at 7K and above, one needs aftermarket rods, bearings, and some oiling mods. Its not an issue with CIS engines,....

We recently did such a 3.2 (based on an early SC) with PMO's and mod-S cams. and it made over 260BHP with SSI's and OEM early muffler. It was 270+ with a better muffler,...

I had the JE's I purchased machined down to a lower CR to keep my single plug ignition. Rather than use the Mahle domes, seems to have worked very so far.

[Steve@Rennsport]

Originally Posted by Scott R

I had the JE's I purchased machined down to a lower CR to keep my single plug ignition. Rather than use the Mahle domes, seems to have worked very so far.

Those work OK, but one cannot use as much advance as the wedge domes that these specific Mahle ones have and that translates into HP & torque.

We see this clearly on the engine dyno when tuning the motors.