 911 CIS Motors, Has anyone run high compression pistons? |
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| Justinp71 |
 Feb 8 2007, 12:04 PM
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Senior Member  Group: Members Posts: 1,583 Joined: 11-October 04 From: Sacramento, CA Member No.: 2,922 Region Association: None 
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In Wayne, "how to rebuild and modify porsche engines" book one of his "top engine picks" on pg 113 he shows a high compression 2.7l with 964 cams.
When I called Rennshift about piston prices they recommended not to run High compression pistons in a CIS motor b/c your cylinder head temp will run high from not getting enough fuel. Anyone have any experience with this? |
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| Eric_Shea |
Feb 8 2007, 12:16 PM
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains  |
No "real world" experience but, I have a 930/07 engine and when contemplating what to do with it, everything power wise related to HC and lumpy cams. None of which work with CIS.
CIS systems use mild cams (hence the stock 964 cams). CIS does not like intake pulses. Because of the weird piston in the CIS motor... there's not much in the way of a cam you can do so you would "have" to get some different pistons. I'm not familiar with Wayne's book or the HC 2.7 CIS motor but those things don't sound quite "right". Meaning, I can't really comment on it because I've yet to see it, build it or even drive it but a HC CIS combination seems to go against standard theory. The folks at Rennshift sound a little more on target. |
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| Eric_Shea |
Feb 8 2007, 12:17 PM
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
P.S. I'm building mine (930/07) with 9.5:1 JE's, S-Cams and MFI.
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| TravisNeff |
Feb 8 2007, 12:23 PM
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#4
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914 Guru Group: Members Posts: 5,082 Joined: 20-March 03 From: Mesa, AZ Member No.: 447 Region Association: Southwest Region
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Take a peek over at the 911 pelicanparts BBS. There is a thread going on about CIS cam selection and pistons/compression. Sounds like some were doing 9.8 to 1 JE pistons, 964 cams in a 3.0 engine. There is other talk of 2.7 engines and short stroke 3.2's all using CIS with modifications
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