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DISCUSSION => Engine + Driveline => Topic started by: Serge on July 24, 2009, 12:03:18 AM

Title: Engine Compression Figures?
Post by: Serge on July 24, 2009, 12:03:18 AM

Just did a compression test on my m42 and all cylinders showing 180psi, is that a good or a bad reading, what is the factory spec? cheers.

Title: Engine Compression Figures?
Post by: phrunt on August 05, 2009, 08:50:17 PM

Normal Compression is 142-156 psi, cylinders should not differ more than 7 psi. The reason for your high readings may have to do with the temperature of the engine, take the reading when the engine is slightly warm, about a quarter way down the temp gauge.

Title: Engine Compression Figures?
Post by: bbarnumboy on August 20, 2009, 05:05:58 PM

142-156?   wow i just did a head job on mine and used the stock thickness head gasket etc. and with the engine slightly warm i just blew a 215 on 2 cyl and a 220 on 2 cyl  anyone explainw hy it is so high?  before the head job i blew a 200 180 190 and a 90....the 90 was because of a cracked head.  ad now after the had job it is  215 215 220 220

Title: Engine Compression Figures?
Post by: JP 91iS on August 20, 2009, 06:45:09 PM

Mine were 220 across all 4.  I searched and most people were showing 180 and above so that lead me to believe that the figures listed in the Bentley are the lowest acceptable numbers.