what is the proper compression for a SC
 

hi all,

i am looking at a 1979 911sc....it seems that the car runs and starts just fine. i thought that i heard an exhaust leak (possible head stud) so i did the compression. it head a consistent 112 to 121 on all six... IS THIS LOW? i dont know how many miles are on the car as the odometer is broken. it has the tensioners and 930 fan etc...

what kind of compression figures are you guys getting? could these be low compression type pistons.. what do they get....thanks...i appreciate it...

My '79 911 SC shows 148 to 151 psi across all cylinders when dead cold.
The vehicle only has 60,000 miles and has lived on Mobil 1 for at least the last 30,000. It has had very good care since new.

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1979 911SC Coupe

Those do seem to be low for an 8.5 to 1 engine ... 145 to 160 psi are the normal range numbers for an engine in good running shape of that compression ratio. That one sounds a bit tired and is probably ready for a rebuild.

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Warren Hall
1973 911S Targa

Should compression be measured cold? Is compression higher when warm?

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'83 SC