Ooops...just finished doing a compression test. But I forgot to press the throttle all the way down while I cranked the motor. How off is my results from not doing this?

What is the purpose of holding down the gas pedal while cranking? Is it to ensure the throttle butterfly valve is open so the intake can suck air into the cylinders? Are you suppose to crank the motor (in 3-4 second spurts) till the pressure no longer moves on the gauge tester?

 

Can't comment on how far off your results are. I'd suspect they're way off, but that's my seat of the pants guess, since the throttle was closed. Should be in the "200's" if your motor is in good working order. If not, re-test the correct way.

 

With the throttle open on mine, the results were only 10 psi higher.

Throttle closed: 235-240
Throttle opened: 245-250

For compression comparison, I have a B18C5, head milled 12 thou(11:1 or so)..

 

Thanks Mike. My results were as follows (with the throttle closed):

215-205-215-215

In cylinder number 2 (I got 205 psi on), there were rust colored stains on the spark plug boot and on the ceramic of the spark plug. This is an indication of moisture or water present on the boot at one time or other? Anything to be concerned about?

Does anybody have pics of a brand new stock ITR spark plug? Mine looks like the electrode is worn but it might just be that way stock.

 

Mine were pretty much the same with throttle closed or opened.

250-255 PSI @ 7 cranks