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Registered
Join Date: Mar 2006
Location: Waterloo, ON, Up North
Posts: 287
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Uber Compression
Picked a motor from a wreckers..
An '83 944, 120,000 on the odo. Ran a compression check this morning and got some insane numbers: All cylinders ran 205 psi, 215 with oil! Im confused, folks. My good friend Hayes says I should be getting 145psi...anything higher indicates an extreme carbon buildup on the head. This motor looks all original. I doubt it was ever opened up. Any thoughts? Is there somethin I gotta do with the '44 motor before checking compression?
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'86 Porsche 944, Guards Red Nancy is currently [going in for the final 'once over' this week..] AFJuvat - "Thou art affirmed: Go forth and inject fuel my son." LOL |
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08-16-2006, 06:40 AM
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Feelin' Solexy
Join Date: Oct 2003
Location: WA
Posts: 3,788
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Is it possible that there is a significant amount of liquid in the cylinders? The only way I can concieve of this heppening is a smaller area/volume for the gases to compress...
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Grant In the stable: 1938 Buick Special model 41, 1963 Solex 2200, 1973 Vespa Primavera 125, 1974 Vespa Rally 200, 1986 VW Vanagon Syncro Westfalia, 1989 VW Doka Tristar, 2011 Pursuit 315 OS, 2022 Tesla Y Gone but not forgotten: 1973 VW Beetle, 1989 Porsche 944, 2008 R56 Mini Cooper S |
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08-16-2006, 07:03 AM
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Nothing special you should have to do to check the compression other than pull all plugs and spin the motor. I just checked the shop manual and it says the compression should be 145 or more. Not sure how to take that really but I'm assuming that means that the compression should never be under 145 but they are not telling you what the maximum should be. My 87 has compression numbers of 190 to 195 per cylinder and when I tore it down, there was no carbon anywhere to speak of and no liquid in the cylinders....everything looked normal.
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Tom 1990 944S2 Cabriolet 2002 Chevy Silverado 2500HD 2003 Maroon Ford F350 dually Last edited by Razorback1980; 08-16-2006 at 08:55 AM.. |
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08-16-2006, 08:21 AM
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Back from Beyond
Join Date: Nov 2004
Location: Alberta, Canada
Posts: 2,697
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Mine checked out at 175psi across all four when I got it. Is 205 abnormally high? You could check the serial number to make sure it's an '83 engine. What are the specs for the Euro motors? Does seem very strange, though. Wish I knew more about this.
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'88 944 Auto - project, kinda '87 944 Auto - died saving my wife '84 944 5SP - crushed under shop roof during snow storm All others GONE! |
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08-16-2006, 08:50 AM
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Join Date: Mar 2006
Location: Waterloo, ON, Up North
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Funny you should mention the Euro motors cuz thats exactly what my first thought was. (Crosses fingers)
The motor looks like its been sitting for a long-ass time..
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'86 Porsche 944, Guards Red Nancy is currently [going in for the final 'once over' this week..] AFJuvat - "Thou art affirmed: Go forth and inject fuel my son." LOL |
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08-16-2006, 01:16 PM
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Registered
Join Date: Mar 2006
Location: Waterloo, ON, Up North
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Heres another question for ya..
what are the consequences of running this (possibly,) 1983 Euro motor with its higher compression using an '86 US DME? I hear the cam is a little shorter on an '83 than on later cars..since the DME in my '86 is geared for the timing of an '86, I thought I might just switch the cam assembly to maintain the timing...ie. the DME just carries on completely unawares of the motor from an '83 lol
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'86 Porsche 944, Guards Red Nancy is currently [going in for the final 'once over' this week..] AFJuvat - "Thou art affirmed: Go forth and inject fuel my son." LOL |
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08-16-2006, 04:10 PM
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Registered
Join Date: Jun 2004
Location: Granite Falls, WA
Posts: 543
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Re: Uber Compression
Quote:
As far as the 205 PSI reading goes, I can tell ya that my '83 HAS a shaved head on it, and its reading close to that (more like 190-195lbs around the horn, with it shaved approx. .018", and running the stock sized gasket). You may have a similar situation here. Also consider your compression gage. They are not all created equal, and can vary, somewhat in what they'll read. The real key is the process in which you use to test compression on each cylinder, and the relationship of the numbers between them all. 145psi is a fairly low end number to me. NOT that the carbon build up couldn't be part of this equation also. You can also ruin a compression gauge by putting oil into the cylinders and checking it that way IF your not careful about it, by not going overboard with it. IMHO. "Looks", can and are almost ALWAYS, decieving (how could you know, unless you took it apart and measured the head and gasket?). I'd suspect a re-worked head first, verify massive carbon buildup by looking in the plug holes. Euro motor? Whats the engine number? That should tell ya. Good luck! 
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1985/1 944 Granite Red (wife's car. Iceshark is lighting her way) 1983 944 Platinum (my daily) 1985/1 Guards Red (project) |
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08-16-2006, 04:16 PM
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Registered
Join Date: Mar 2006
Location: Waterloo, ON, Up North
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OH rite..thanks for bringing up the engine serial.
43DD479 Prolly shoulda clarified this first but, no..the motor isnt in the car yet cuz of the gaskets and w/e i'd like to replace before-hand.. I bolted the starter on and, with some help from jumper and cables, ran a little compression check
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'86 Porsche 944, Guards Red Nancy is currently [going in for the final 'once over' this week..] AFJuvat - "Thou art affirmed: Go forth and inject fuel my son." LOL |
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08-16-2006, 04:26 PM
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