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Registered
Join Date: Jan 2003
Location: Annapolis MD
Posts: 1,020
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Dropping C/R on 993 engine
I just got done talking with Charles @ LN about pistons and reconditioning my mahle barrels.
So my question is .... Is it worth dropping the C/R down from the 993 stock 11ish to say 10.5-1 or just get the 11.5-1 JE pistons he has in stock? Seems that >11 CR isnt going to work with carbs running 93 pump gas. I am still going to run PMO carbs. Im not sure how much timing I can retard to make it work but dont want to loose too much power. Hoping that Henry or Steve chime in. Thanks |
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10-30-2013, 01:33 PM
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Join Date: Sep 2005
Posts: 950
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If it were me and wanted faster replies. I would post the inquiries on Steve's Rennsport forum.
Good luck with your upgrade. |
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10-30-2013, 02:40 PM
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Join Date: Jan 2003
Location: Annapolis MD
Posts: 1,020
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What forum is this .. Ive never heard of it?
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10-30-2013, 02:44 PM
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Registered
Join Date: Sep 2005
Posts: 950
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Surf Steve's website for info.
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10-30-2013, 02:49 PM
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Location: Annapolis MD
Posts: 1,020
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Thanks ... been on the site before but never saw this part.
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10-30-2013, 02:56 PM
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Join Date: Jun 2004
Location: Oxford, Ct.
Posts: 2,294
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If you actually measure your motor you'll find that the C/R is actually around 10.2-10.4
Porsches C/R numbers are always a little optimistic especially on the 964 and 993
__________________
07 GT3 Cup S 4.0, 00 986, 78 911 old school gt car 77 BMW R100S 99 Ducati 996S 04 BMW R1150R DanielJacobsLLC.com |
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11-01-2013, 05:38 AM
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Join Date: Aug 2010
Posts: 197
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What ignition are you running that has more to do with cr than efi or carburetors
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11-01-2013, 06:14 PM
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Join Date: Jan 2003
Location: Annapolis MD
Posts: 1,020
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Seems like 10.1 CR is the best best. 10.5 "might" be to much. Not worth the risk after a complete rebuild. From what Ive been told so far that JE pistons dont have the squish that the OE mahles have so they tend to work better for the higher compression but dont have the relief cuts to run a wilder carb happy cam like the DC43 - 108 suggested by John D. Im not sure how much this cam will affect the static C/R in the cylinder. Any pros have some background on this?
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11-02-2013, 05:54 PM
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