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Join Date: Oct 2002
Location: Toronto Ontario, Canada
Posts: 214
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Compression Testing a 2.7 with Carbs
Hey Guys,
Bought a nice compression tester last fall and with the weather warming up this weekend I figured I would try it out on the car. Obviously I am going to disable the fuel pump but have questions on the engine prep before the test. My thoughts are to run the test with a cold motor and all plugs in. Is this correct? I figure with the plugs in the back pressure would be more like actual operating conditions?? I have also read that the plugs should be removed cold due to expansion and possible damage to threads on a warm engine??? What procedures are correct?
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TechGuy 1972 Targa 911T/S 2.7 PCA Upper Canada Region |
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03-05-2004, 11:33 AM
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I've always done compression tests with all the plugs removed for two reasons. First the tester screws into the spark plug hole so removing them makes sense and second the starter can spin the engine more easily with them removed so the readings are usually more accurate.
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Email me about 911 exhaust stud repair tools, rsr911@neo.rr.com 1966 912 converted to 3.0 and IROC body SOLD unfortunately  1986 Ford F350 Crew Cab 7.3 IDI diesel, Banks Sidewinder turbo, ZF5 5spd, 4WD Dana 60 king pin front, DRW, pintle hook and receiver hitch, all steel flat bed with gooseneck hidden hitch. Awesome towing capacity! |
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03-05-2004, 12:26 PM
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Oops, one more thing. Yes it is better to remove the plugs cold on ANY aluminum cyl. head.
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Email me about 911 exhaust stud repair tools, rsr911@neo.rr.com 1966 912 converted to 3.0 and IROC body SOLD unfortunately 1986 Ford F350 Crew Cab 7.3 IDI diesel, Banks Sidewinder turbo, ZF5 5spd, 4WD Dana 60 king pin front, DRW, pintle hook and receiver hitch, all steel flat bed with gooseneck hidden hitch. Awesome towing capacity! |
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03-05-2004, 12:27 PM
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Location: Peoples Republic of Long Beach, NY
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I like to unplug the CD,
keep throttle WOT
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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03-05-2004, 01:25 PM
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Location: So. Calif.
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Warm engine to operating temperature
Remove all plugs Ground the coil wire (remove from distributor cap) Open throttle Crank engine for 4 compression strokes (go 8 if you have an early S or with agressive cams); record the last reading Sherwood Last edited by 911pcars; 03-05-2004 at 03:23 PM.. |
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03-05-2004, 02:30 PM
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Location: Toronto Ontario, Canada
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This is tomorrows job finally.
The big question, hot or cold when running test? Plugs in or out?
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TechGuy 1972 Targa 911T/S 2.7 PCA Upper Canada Region |
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07-30-2005, 08:16 PM
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Location: Marysville Wa.
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normal operating temp, plugs out, crank each cylinder about 10 pumps or until the gauge stops moving.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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07-30-2005, 08:49 PM
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Should I back the plugs out a bit prior to running the motor up so the removal is easier and I do not damage the threads?
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TechGuy 1972 Targa 911T/S 2.7 PCA Upper Canada Region |
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07-31-2005, 07:51 AM
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1966 Porsche 912 1981 3.0SC
