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964/993 Crank question!
Just thinking out aloud here, but if one were so iinclined to use a 964/993 crank with 930 97mm P&C's, what would the end displacement and C/R be?
I would guesstimate that using such a setup would yield approx 8.0:1 C/R, correct?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition 
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10-16-2006, 06:17 PM
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Location: Central Fla
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CR
figuring a 91 cc chamber,11cc dome,.040 deck that combo is 7.45 to 1
Mike Bruns |
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10-17-2006, 10:11 AM
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Thanks Mike. Does it affect displacement at all? Would it bump up displacement to, say, 3.4L?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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10-17-2006, 07:34 PM
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Doesn't want/need a 3.6L
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Quote:
 You'll have a long-stroke "3.4L"... 97mm bore x 76.4mm stroke is approx. 3386cc, not quite a true 3.4L but closer than the guys using a 98mm bore x 74.4 stroke (3367cc)... Increasing the bore diameter will always yield a larger displacement increase than lengthening the stroke, but I know what you are trying to accomplish having told you of the "3.5L" long-stroke that Andial builds for both normally aspirated and turbo motors.... Quick cheat sheet so you can ignore the above: 95mm x 74.4mm = 3164cc or 3.2L (stock Carrera) 97mm x 74.4mm = 3299cc or 3.3L (stock 930) 98mm x 74.4mm = 3367 or 3.4L as it is commonly known 100mm x 74.4mm = 3506cc or 3.5L  102mm x 74.4mm = 3647cc or 3.7L 97mm x 76.4mm = 3386cc or long-stroke 3.4L 98mm x 76.4mm = 3458cc or long-stroke 3.5L 100mm x 76.4mm = 3600cc or 3.6L (stock 964/965/993) Ralph |
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10-17-2006, 08:40 PM
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Cool, thanks Ralph.
I'm just thinking out aloud here. If I were to build a pure track car in the future, I think that's the path I'd take (930 P&C's with 964 crank and flame-ringed liners for extra reliability).
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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10-18-2006, 05:02 PM
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Doesn't want/need a 3.6L
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Quote:
I see where you are going with this, using the longer stroke 964 crank for extra low/mid range torque and the stock 97mm piston/cylinders rather than splurging for the expensive 98's which will save you some cash... Ralph |
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10-18-2006, 08:49 PM
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Location: Orange County, California
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Ralph, what's your knowledge of the relative strength of the 964 crank compared to the 3.2/3.3? Merv is a well know boost junkie
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10-18-2006, 09:14 PM
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Quote:
89turbocabmike poses and interesting question regarding relative strength of the 964 cranks. Any answers there?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition
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10-18-2006, 10:59 PM
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Location: north america
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964 cranks are strrrrrrrong but I think the 993 crank is even stronger just because they were built to run without a vibration damper .
The crank is the last thing I would worry about... I worry about those damn rods, to the point where when I rebuil my 95 993 motor I am just going to bite the bullet and get some after market rods so I NEVER have to go back in there for a over rev. At least for a 120k miles
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10-19-2006, 06:30 AM
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Doesn't want/need a 3.6L
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Quote:
My opinion is that both cranks have their shortcomings...some opine that the rod bearing is the real culprit and their lack of durability leads to failures, due to bearing material quality as well as lack of oiling. I've seen some obviously overheated parts at Ollie's in the past, where the heat/friction generated has gotten so hot that the bearing material has flaked off due to excessive heat and too little oil to the area that it can't be properly dissipated. It may also be a factor why many pro engine builders discard the Porsche bearings in favor of apparently better Chevy Bearings for example...some also change the Porsche clearance as well, grinding a thou or so off the rod journals to try and help. Some also prep the crank(s)for more severe use by cross-drilling & grooving the center mains in an effort to get extra oil to #2 & #5. I think for a normal street car (under 6,500 rpm) this all may be overkill work, as there seem to be plenty of cars running around out there without this extra machine work that seem to get along fine. But, you high-horsepower 930/turbo conversion guys that want to rev (don't you already make enough power? ) may want to look deeper into it as it may be more applicable for what you guys are trying to accomplish... You may want to consider using the 993 crank & rods as an alternative, but than again these also seem to have their own issues that not everyone is sold on. One well known shop discards the 993 crank in their 750+ hp 993TT motor in favor of the 964 unit with success, others would never dream of using the 964 crank over the 993 in this type of application. Different strokes for different folks... Ralph |
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10-19-2006, 05:58 PM
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Location: Portland Oregon
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Great subject,....
Some data points to think about: 1) Porsche used the 964 crank in the 993 RSR motor due to its wider rod journals and more bearing area. These used the LWF and RSR rear pulley. Some racers used 2 & 3-plate 5.5" Tilton clutches, too. The 964 crank is a better choice when revs over 7K are anticipated. 2) The # 2 & # 5 rod journals are the last place to receive oil in 911 motors and race engines that will see 7K or more should get the mods that Ralph mentioned; cross-drilling, bearing mods, and case oiling holes opened to match. The helps ensure that these critical bearings get as much oil as the others. This one is a biggie!!!!!!! All this aside, 993 motors that will not see over 6500 RPM do just fine and have no issues. 993 motors that are used for DE events might consider better valve springs & retainers, though as those have not been 100% reliable when operated near redline for long periods of time.
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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10-19-2006, 09:34 PM
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1988 Porsche 911 3.5L Motronic Twin-Plug
