High compression readings

[natwales]

1988 5.7 Merc. My shop manual specs the compression at 150 (or 155 I forget), but I tested it today and got numbers ranging from 165 - 175. That's higher than I expected. I'm not complaining, but is this normal?

 

[Don S]

Re: High compression readings

How accurate is your gauge?

 

[natwales]

Re: High compression readings

I don't know. It's almost brand new. This is the one I was using:

http://www.sears.com/shc/s/p_10153_12605_00947089000P

 

[Don S]

Re: High compression readings

Age of the gauge and where you bought it means nothing, the question is, how accurate is it.
What I do constantly at work is check one gauge against another. I also grab other compression gauges and check them against one another..
I sure wouldn't worry about it. If you had 1 or 2 cylinders with overly high compression readings, that could indicate water. But equal and consistant on all cylinders sounds like a gauge to me. Especially if the engine is running nicely and the plugs look good.