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Join Date: Dec 2006
Location: Denver
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3.4 Upgrade??

Since the purchase of my 930 a couple years ago (104,000 mile Euro car)I have always been worried about how long I have until the motor lets go as my car sat for 15-20 very neglected years. I did have a leak down done on the engine not sure what the exact numbers are, but were surprisingly good. On the flip side the engine drips oil at a high rate of speed from all over.

I have been going through the process of refreshing the car and enjoying driving it along the way knowing that the motor will be the next thing I spend some time and money on. I plan on driving it through the fall and having a fun winter project. Seeing this coming like a freight train, I have been buying up a stash of parts gaskets, bearings, and even a set of 964 cams (Ground by Web), K27, & B&B intercooler.

Since the engine leaks so badly I am planning on a complete tear down. And expecting the worse case. The one thing that I have been trying to learn about is the crankshaft and what options I may have. I am hopeful that when that engine comes apart I can send it off to be polished. I am not sure that I am game to have it ground because I am worried that it could damage the crankshaft and cause serious damage to a new motor? The 3.3 or 3.2 crankshaft seem to be non-existent in a standard/standard form these days and the couple I have come across cost more than a GT3 piece.

On down the slope... Again I am hopeful my crankshaft is fine, could use a polish, and be good to go. And at this moment I realize a GT3 crankshaft can be installed to create a 3.4?? From my understanding I go down to my local Porsche dealer put in the order for the GT3 crankshaft, buy a set of Pauter rods, slap it in, and POOF! 3.4 torque monster.

Yeah right, nothing is this easy with these cars ever! Can someone enlighten me? What else am I going to need? are the main bearings the same? I assume I would get a set of GT3 bearings? What GT3 crankshaft do I actually buy? Oh and what about the pistons? Do I need a totally different set of P's & C's.
Old 04-21-2014, 07:19 AM
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I made mine into a 3.6 stroker.... you have email
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Brad...930 gt-1 racecar, increased displacement to 3.6L, JB racing Cylinders, JE 8 to1 pistons, stroked crank, Carrillo rods, extrudehoned 3.2L intake, full bay Bell I/C, GT-2 EVO cams, Rarly8 headers, GTX-35RS turbo, twin plug, P&P heads, Link G4 EFi system, G-50/50 with LTD slip and oil squirters/oil cooler, zork tube, full race coilover system, with carbon fiber body, full cage, E-85 sippin drunk
Old 04-21-2014, 07:36 AM
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i would pull it and do a top end as long as you have good oil pressure and feel the bottom end is good. put in all your new goodies and drive it another 100k and then do the rebuild.
this would also stop th eoil leaks.
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Old 04-21-2014, 07:36 AM
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Stroke

Dear cdill,

When you stroke up an engine you have to take several points into your consideration.

First of all clearances - which in this specific case it not critical at all - the difference from the 3,2 / 3,3 crank to the GT 3 crank is from 74,4 mm to 76,4 mm just two millimeter.

So under the line it goes one millimeter more up and one millimeter more down.

Depending on the conrod configuration you just have to get the cylinders adjusted in length with cylinder to block spacers, this is also uncritical in a certain range.

What you have to focus is the change of static compression ratios if you modify bore and stroke the same time.

The length of the conrod will also influence the adiabatical compression and different to a normally aspirated engine the longer conrod is not automatically the better conrod.

Anyhow - the common lengthes in Porsche engines are between short and too short so not the biggest point in this coherence.

So when your static compression ratio is rising you can react with an appropriate camshaft on the dynamical side.

Just give it a little more lift in TDC and you are fine; making the best out of it.

When stroking up an engine you should use the opportunity to work out a most possible perfect working squish band - this is one of the most important points and very often underestimated if not unconsidered at all.

Detonation and pinging is to be found and resolved there.

If you are in need of any crank just let me know - for example I have the requested 74,4 mm std. available ex stock as well as 76,4 mm / 80,4 mm / 82 mm / 84 mm.

All this together with the Porsche Titanium conrods or our own steel versions.

By the way we also produce and offer pistons for those application made from Mahle 124. Due to this Material combined with a special heat treatment this pistons are very very reliable and good for the hardest possible application.

Remaining with best regards,

Dirk
Old 04-21-2014, 09:13 AM
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+1 "Yeah right, nothing is this easy..."

You can install GT3 conversion rods, but increase the rod angle. Hardly optimal.

Install standard length semi-custom rods, and piston + head machining. Charlie Foxtrot.

Install one of the GT3 rods (yes, I know there's 3 different ones) + new pistons = ideal.
Plus modify the GT3 crank & original pulley.

Last one of those we put together LOVED cams bigger than 964s, had huge torque at 3,000rpm, pulled like crazy to 6,500rpm, and was glass smooth all the way.
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Old 04-21-2014, 06:13 PM
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Cam it up too

Hi again Chris,

so let's find our way out of the " pussy cam trap " !

And hold in mind that the long conrod is supporting the exhaust - which it is leading the way to modern asymmetrical profiles.

So why not going a next step together with good old mother 930 - the best car ever !

Best reg.

Dirk
Old 04-21-2014, 11:43 PM
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Hi cdill. If you have a nice running good oil pressure engine,other than your leaks i would think your existing crank will be fine. A fantastic addition to your full rebuild would be a nice set of fully finned mahle 3.4 pistons and cyls. 1mm deck height and with your cams your car should be a rocket. If you are running the stock cis fuel system then you will need more fuel by way of modded metering head and wur. Dont forget to grab some arp rod bolts and head studs!
Old 04-22-2014, 05:57 AM
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Ha ha, Dirk -- exactly right! Once you get away from the little factory cam profiles, it is shocking that (a) the torque at 3,000rpm is night-and-day better, (b) the engine makes more power and carries to a higher rpms, and (c) the engine still idles just fine with strong manifold vacuum.

cdill --
No matter which direction you choose to take the rebuild, I'd always recommend installing ARP head studs, ARP rod bolts (if not changing the rods), upgraded valve springs, and coated engine bearings.

If you stay 3.3L, the 964 cams are good, but there are better. They frequently require machining the top of the piston for additional valve clearance, but this is quite easy to do.

I also agreed that if oil pressure is good, it's likely your crankshaft is good and reuseable, only basic refurbishing required.

If you stroke the engine, it will be a torque monster. Sure, 98mm cylinders would be sweet, and we've done several with slip-fit 100mm cylinders, but you won't be disappointed with a 97mm bore stroker.
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Old 04-22-2014, 12:45 PM
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the magic of stroke

Yep Chris,

you are so right cam and also stroke wise !

And after all the Porsche Engine likes stroke.

It makes a very elastic and torquey engine - not to forget that the possible smaller bore makes a more compact combustion chamber which is very good for any turbo engine anyhow.

Since the 76,4 mm GT 3 crank is so cheap and a set of high quality 98 mm P+C is not coming for free it makes good sense to think it over.

This GT 3 crank is by the way a nice peace of construction also in its oiling strategy.

Best reg

Dirk
Old 04-22-2014, 03:35 PM
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Thanks to all that have replied.

When the time comes I will most definitely split the case on this one and replace the bearings etc. I would just hate to have the motor out and apart and not freshen up the entire thing. The 3.4 idea seemed like a good one, but after realizing what is involved I am not sure that I will go this direction. I love to modify my cars, but with the values soaring I may want to cash out some day and want the ability to go back to stock.
Old 04-23-2014, 08:12 AM
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