[Prev][Next][Index][Thread]

<MISC> Compression Testing BMW Engines

I have a compression meter which consists of a gauge, a long stem, and a
screw-in adapter that goes in the spark plug hole. The sparkplug adapter
is shorter than the spark plug, but about 3/8 of an inch. 

Thus, when I do a compression test, I expect slightly lower numbers, since
the short adapter allows for more compression chamber volume. Thus, this
mail: has anyone out there a good idea of what the expected decrease in 
measurements would be for this type of gauge? That is, for my 84 3.2L engine,
Bentley's says I should get 160 PSI on each cylinder. I measure 140 on lots
of cylinders, nothing higher. Does this 20PSI differential sound plausable,
or should I lay out another $50 or so for a newer gauge with a longer spark
plug adapter interface (can't seem to get a new one for my unit - tried 
already).

Any  correspondence welcome,

David Hoerl
84 633CSi
78 320i