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964 RSR case mods.

A friend bought this for $100 !
Thought it could good to post some pictures for reference.







From the inside:



Unfortunately this explains the $100





Will make a nice table stand thou.

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Magnus
911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI.
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924 -79 Rat Rod EFI/Turbo 375whp@1.85bar.
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Old 06-12-2010, 09:56 AM
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where is the "from the inside" pic located in the case?
Old 06-12-2010, 02:39 PM
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PFM PFM is offline
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Funny they still do all that useless boat tail work ....I wonder why????

I thought some here say that it is useless work with no gains to be had. Was that factory work or a local machine shop?

PFM
Old 06-12-2010, 06:16 PM
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Quote:
Originally Posted by Emery G. View Post
where is the "from the inside" pic located in the case?
Between the cylinders.
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Magnus
911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI.
911T Coupe -69, 3.6, G50, "RSR", track day.
924 -79 Rat Rod EFI/Turbo 375whp@1.85bar.
931 -79 under total restoration.
Old 06-12-2010, 11:21 PM
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Quote:
Originally Posted by PFM View Post
Funny they still do all that useless boat tail work ....I wonder why????

I thought some here say that it is useless work with no gains to be had. Was that factory work or a local machine shop?

PFM
We guess its factory. Thats why he bought the case, to see if they had done anything special to it.
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Magnus
911 Silver Targa -77, 3.2 -84 with custom ITBs and EFI.
911T Coupe -69, 3.6, G50, "RSR", track day.
924 -79 Rat Rod EFI/Turbo 375whp@1.85bar.
931 -79 under total restoration.
Old 06-12-2010, 11:24 PM
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Windage mods do work, it is just that the gains are only noticeable in a racing engine which spins very fast for most of its life and spec (Carrera Cup) racing can make small horsepower differences more noticeable.
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Old 06-12-2010, 11:29 PM
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Quote:
Originally Posted by safe View Post
We guess its factory. Thats why he bought the case, to see if they had done anything special to it.
I have talked with a number of factory guys that have stated they have never seen a factory motor modded this way. The GT3 cups are a great example as there are no mods done to the case at all.

Most,if not all of the mods are done thru the independent shops running the cars.
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Old 06-13-2010, 08:05 AM
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The GT3 Cups do not use the windage mods because they use an excess-flow oil scavenge pump. They draw down the air pressure in the case to negligable levels. Since there is no air in there, there is no point in shaping things aerodynamically.
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Old 06-13-2010, 09:34 AM
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Aaron is correct.

The factory doesn't do those case modifications on cars delivered to customers. That was done by a professional engine builder.

For engines that live above 7K, it does make a measurable difference in power.
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Old 06-13-2010, 09:44 AM
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Do the 964 Cups use crankcase vacuum also?
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Old 06-13-2010, 09:50 AM
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Quote:
Originally Posted by Flieger View Post
Do the 964 Cups use crankcase vacuum also?
No, they were normal.

They were not shuffle pinned either as far as I can tell. The case was simply "houred" out and replaced with a new case. You can see a great deal of fretting on the houred out cases.
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Old 06-13-2010, 01:46 PM
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We tried a GT3 negative pressure valve on the dyno with a GT3 oil pumped engine and found no HP difference. Thinking about it though, maybe we should have held the engine at high RPM for a while to generate crankcase vacuum and then we may have seen a difference. Oh well.

Perhaps the valve system needs the two extra scavenge pumps that the GT3 has on the exhaust cam boxes to make the crankcase vacuum system work?
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Old 06-15-2010, 06:58 AM
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Quote:
Originally Posted by Cupcar View Post
We tried a GT3 negative pressure valve on the dyno with a GT3 oil pumped engine and found no HP difference. Thinking about it though, maybe we should have held the engine at high RPM for a while to generate crankcase vacuum and then we may have seen a difference. Oh well.

Perhaps the valve system needs the two extra scavenge pumps that the GT3 has on the exhaust cam boxes to make the crankcase vacuum system work?
The case is isolated from the cam boxes on the GT3 so the main oil pump just scavanges the case.
Were you able to verify you had case vac?

Did you use the special rear main seal? If not you will pull air thru the seals and not produce the required vac to see the HP increase. FYI you can simply install the stock rear main seal backwards and it should work fine.

The other vac specific parts are low tension rings.
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Old 06-15-2010, 07:49 AM
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You are exactly right on the cam boxes being separated from the crankcase on the GT3, thus camshaft oil never returns to the crankcase and the main scavenge pump is free to pump more air instead.

The engine was built on 2.0 alloy case, so had early, small main seal.

We didn't measure case vacuum.
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Old 06-15-2010, 08:56 AM
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If you atempt it again, please keep me posted. I've been wanting to do it for some time now.
Cheers!
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Old 06-15-2010, 09:03 AM
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How much vacuum is required for windage mods to not be necessary? I'm guessing the. motorsport cars have an electric vacuum pump of some sort? Any details on specs or part numbers?
Old 06-17-2010, 08:59 AM
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There is no electric vacuum pump. Just a huge oil scavenge pump, in the GT3 with two pickupsv just for the case plus the afformentioned cam box pumps. When to use a GT3 vs 930 pump?
Because there is so much extra scavenge flow (fixed displacement pump) the pump sucks some air out, too.

All oil scavenge pumps are actually sucking a mixture of oil and air. This "foam" varies in density due to rpms. That is the reason for the baffles in the oil tank- as an air/oil separator.
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Last edited by Flieger; 06-17-2010 at 10:40 AM..
Old 06-17-2010, 10:34 AM
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all dry sumps run a slight neg pressure in the cc. The GT3 just added a one way valve and larger scavenge section w/ special crankshaft seals to enhance it. In the hot rod world where thay run american push rod V8s w/o dry sump they sometimes add electric(or other pumps) to generate neg cc pressures

Jason Andreas posted these pics of the GT3 cc breather valve & seals




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Old 06-18-2010, 06:12 AM
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Pretty cool info. I didn't know a dry sump system could pull enough vacuum to make aero mods not necessary, at least for street engines.
Old 06-18-2010, 08:07 AM
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Piston rings also seal better without positive crankcase pressure. This probably results in more net power gain than the mods for internal air flow, but for a max-power engine, every thing helps.

MHO,
Sherwood

Old 06-18-2010, 08:51 AM
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