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Location: Encinitas (San Diego CA)
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which route would you go: used 993 v-ram OR rebuilt 964 w/ 993 heads

Esteemed members-
I'm at a crossroads and keep thinking of more power. I have two opportunities both of which seem to have their plusses and minuses. I currently have a 3.2L ('86) w/ '86 915 and drivetrain. Engine would go in my lightweight, early RSR clone and be used only for fun driving or track. This is not a commuter car ;-)

What would you do???:

I have the opportunity to buy a 46k mile 993 v-ram (1996) factory engine. I would probably just install it and enjoy it and keep it stock, maybe add factory solid lifter RSR cams and non-hydraulic rockers. Engine has good compression and leakdown #s. This is a euro motor with obd1 harness and chip-able DME. I'd be using Patrick motorsports lightweight flywheel and a SACHS powerclutch kit. Comes from a reliable source.

OR

I could buy a 964 - based rebuilt engine, w/ mahle pistons, 993 heads, RS spec cams, '95 fuel injection and '95 DME. I don't know compression ratio, yet, but assume 11:1 range. This also comes with lightweight flywheel, FG engine tins, centerforce clutch and other conversion hardware. Engine was spun balanced and comes with other lightweight components like crank pulley. This was built by a known technician.

Costs are essentially EQUAL bewtween the two, maybe a slight advantage to the rebuilt motor.

Thanks,

Doug
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1971 RSR - interpretation

Last edited by DW SD; 11-04-2005 at 02:11 PM..
Old 11-04-2005, 02:01 PM
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I would probably go w/ option 2 but it would be real close.

both engines have ~11:1 cr so that's a draw

the RS cams are a plus, were bigger valves used? any port work?

the '95 intake /FI is easier to work on w/ less to go wrong, less to maintain, makes comparable power at the top, vram has better midrange torque, so if you can keep it on the cam there is little or no disadvantage w/ the simpler setup.

vram heads have bigger intake valves than '95
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Bill Verburg
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Old 11-04-2005, 04:08 PM
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Bill,
You are just the man I was hoping that would respond!

Good opinoins.

I'll sniff out info about the heads option two. I thought he said they are v-ram, so the valves would be bigger. I know he used the AASCO keepers and springs, too, which is also a plus. I think AASE brothers did the machine work. My conversation was not highly detailed, yet.

What are the downsides of using a 964 crankcase?

Thanks again,

Doug
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Old 11-04-2005, 04:13 PM
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Some folks prefer the 964 crank and rods, I feel that the 993 is more robust but it's really a toss up. The 964 is reputed to vibrate more w/o the damper, the 993 never had one. W/ solid mounts they will both shake the car at idle.
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Old 11-04-2005, 04:20 PM
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Thanks again!

Is dynamic balance of the rotating assembly the right thing to then for both 993 or 964 motors? Does the factory do it?

Doug
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Old 11-04-2005, 04:30 PM
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The 964 crank & rods are more robust than the 993 parts are.

Porsche never raced anything with the 993 crank due to its narrower rod journals. 993 RSR race cars and GT-2's raced with a special version of the 964 crankshaft.

Both are pretty smooth as long as everything has been properly balanced.
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Old 11-04-2005, 06:00 PM
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Like I said different opinions. The 993 crank is 1kg heavier has thicker flanges(that's why the rod journals are 3mm narrower(less friction, stiffer). The whole recipricating/rotating assembly however is lighter, stiffer and revs more freely.

The 993 crank was further developed in the GT3

From the Technische Information Ersatzteile Katalog
Rennversion Modell '97
the GT2 crank is a 993 variation
993.102.021.02
as are the rods
993.103.020.06>R<

The vibration felt in all 911/964/993 engines is a moment of the secondary component of the second-order vibration( arocking couple). It causes the engine to try to rotate clockwise then cc as seen from above. It is most noticeable at idle w/ solid mounts and has nothing to do w/ rotational or recipricating balance.

For a street or semi street motor I'm sure that there is little difference between the 993/964 except that I would keep the damper on a 964, I resect the factory engineers decision to put it there. The 964RS engines that I have seen w/o the damper are reported to vibrate a bit more than their damped sisters. I suspect that this is the the crank whiping around a bit
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Old 11-04-2005, 09:52 PM
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hallo
Depends on what you want to do with the Car , mostly Street with some Track events , take the Stock engine .
Mostly Track and street use only to get to the Track , go with number 2 , make sure it has Mahle Pistons and original not bored Cylinders . This Engine is clearly set up for Track .
If something goes wrong it is easier to replace Stock Parts , than special ordered Stuff .
To me it is a matter of what you use the Car for .
Harald
Old 11-05-2005, 12:20 AM
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Old 11-05-2005, 12:20 AM
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