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Old 09-25-2008, 09:20 PM   #1
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Is the 3.4 and 3.6 based of the 3.2?

Hey guys so Im having an argument with my dad about the fact that the 3.4 and 3.6( GT3) are not based of the 3.2. He thinks that they are just the 3.2 made bigger with different components. Can anyone explain this to me or show me links explaining if the 3.4 and 3.6 are or not based of the 3.2.

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Old 09-25-2008, 09:36 PM   #2
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Maybe just some clarification is needed. The Boxster and Carrera share the M96 block which is available in 2.7, 3.2, 3.4, 3.6, and 3.8L. The GT3 and Twin Turbo share a 3.6L based on the old 964 block. Two very different engine designs. No IMS issues on the GT3 motor.
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Old 09-26-2008, 05:44 AM   #3
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Quote:
Originally Posted by Topless
The GT3 and Twin Turbo share a 3.6L based on the old 964 block.
The engine on the TT, GT3, GT2, GT1 race car and 959 are all related and date back to before the 964. They are actually evolutions of a design that started with the 904 and 962 in the mid-60s.

I think that line ends next year though, I believe I say that Porsche announced all the engines in the new 997s will be based on the same block.

All the other 986, 987, 996, and 997 engines from 3.2-3.8 liters share the same block with different cylinder bores. The heads from different displacements and different years vary greatly.

Last edited by blue2000s; 09-26-2008 at 05:48 AM.
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Old 09-26-2008, 08:17 AM   #4
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here's how the M96 variants (non GT2, GT3 or Turbo) are pieced together (if i remember correctly):

the 2.5L and 2.7L engines share castings. the heads are identical and the bores are identical, but the stroke is slightly longer on the 2.7L (different crankshaft).

the 3.2L and 3.4L engines share castings and heads as well. i believe they also share cranks, but that their bores are different.

the 3.6L and 3.8L share castings and heads; the 3.8L has a larger bore.

The GT2, GT3 and Turbo engines are all more or less the same (and totally unrelated to the M96); the valvetrain on the NA is a bit different than the one on the turbo variants i think; the compression ratios are obviously different as well.
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Old 09-26-2008, 06:43 PM   #5
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All I can say for sure is a 2002 996 3.6 bolts right up to a 1998 5 speed tranny in a 1998 Boxster.
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Old 09-26-2008, 07:00 PM   #6
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All I can say for sure is a 2002 996 3.6 bolts right up to a 1998 5 speed tranny in a 1998 Boxster.
correct; all of the M96 variants have the same bell housing pattern. the GT2, 3 and turbo all mate up to the split case trannys.
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Old 09-26-2008, 07:14 PM   #7
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The cylinder heads changed twice on the 3.2, twice on the 996, and once on the 997 and they were all different part numbers.. That's not counting the high power packages. There are many different heads for these engines.
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Old 09-26-2008, 07:45 PM   #8
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If the blocks are all the same, why was is it that the lowly little 2.5L 98/99 Boxsters are the only ones that catastrophically crack their little cylinder walls? If anything I’d think they’d have thickest cylinder walls.

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Old 09-26-2008, 07:55 PM   #9
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Originally Posted by pk2
If the blocks are all the same, why was is it that the lowly little 2.5L 98/99 Boxsters are the only ones that catastrophically crack their little cylinder walls? If anything I’d think they’d have thickest cylinder walls.

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A couple of misconceptions here. The castings for the 2.5 and 2.7 are not the same as the 3.2 and 3.4. So the outer cylinder wall diameter is not the same. Also, cylinder wall cracking is a BIG issue on the 3.4. Cylinder sleeve slipping is the more common issue on the 2.5. It's a different failure mode.
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Old 09-26-2008, 11:48 PM   #10
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Quote:
Originally Posted by blue2000s
A couple of misconceptions here. The castings for the 2.5 and 2.7 are not the same as the 3.2 and 3.4. So the outer cylinder wall diameter is not the same. Also, cylinder wall cracking is a BIG issue on the 3.4. Cylinder sleeve slipping is the more common issue on the 2.5. It's a different failure mode.
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Thanks for the reply.

My mistake, some post here implys that the blocks were all the same.

I read a couple extensive and contradictory descriptions of sequence of events that result in catastrophic failure the 2.5. The net result though seemed to end up with a chunk out of your cylinder wall flopping around.

I wasn’t aware that the 2.7 suffered the same fate as so many 2.5’s. Just plain was not aware of 3.4 problems at all.

You seem to be implying then that a 3.6. is the only worthwhile upgrade. (not much more point or bang for the buck with a 2.7 or 3.2 swap)

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Old 09-27-2008, 06:36 AM   #11
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I think cylinder walls have cracked on every engine, but it seems to be the biggest problem on the 3.4. There's no statistical info on any of this. Is a 3.4 a worthwile upgrade for the risk? It all depends on the individual.
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Old 09-27-2008, 09:05 AM   #12
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Quote:
Originally Posted by blue2000s
I think cylinder walls have cracked on every engine, but it seems to be the biggest problem on the 3.4. There's no statistical info on any of this. Is a 3.4 a worthwile upgrade for the risk? It all depends on the individual.
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Mmm, All I’ve ever heard about here and elsewhere is the 2,5’s. “LN engineering” (Nickes) and” Flat 6..” (our sponsor) dosn’t seem to discriminate though, so I guess your right.

I does seem 98/99 2.5L’s were particularly vulnerable. I had read some where that after some year they had sorted it out though. I’m just doing advance reconnaissance. I have 35k mi. and am pushing it pretty hard.. I’ll be amazed if dosn’t become another ugly statistic before long.

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Last edited by pk2; 09-28-2008 at 07:47 PM.
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Old 09-27-2008, 04:30 PM   #13
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The 3.2, 3.4, and 3.6 share the same block. Hence, the 3.4 and 3.6 have thinner cylinder walls than the 3.2, which is partly the reason you rarely hear about 3.2's D-chunking. I don't know what they did to create the 3.8.

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