Leak it down...anything else is just a child's play test by comparison.

 

only way to tell for sure.

 

Darien-
Just saw this. Looks like there's overwhelming consensus to do the leak down.

You asked what the compression should be. Hard to say for sure. I have a HF compression tester that will read about 155-165, whereas my friends reads 180-190. The key is to look for consistency. You obviously do not have consistency. I'd re-do that entire bank just to make sure.

 

This was interesting to me:
Anyone know how that would happen?
But it could explain your #8.

 

The compression reading will vary due to the volume of the hose of the compression tester since it is effectively adding volume to the cylinder. So a tester with a longer hose will give lower readings.

 

5 and 6 are a little on the lower side. The rest are within the +-10% acceptable range. But since you engine is boosted, the lower compression on those two cylinders is not that important. Did you keep the throttle at wide open during the compression test? You can get some low and inconsistent numbers if the throttle is closed.

 

Test again Darien, from the beginning. Start with 8 or 5 this time. You are going to get entirely different numbers.

 

I've heard that before, but not sure how I can have the throttle wide open with the throttle body removed

 

Will do

 

Can't get any wider than that

 

please!!!!

you go about 5-6 hits and any length of hose is a non issue.

my 84 with 176000miles on it was in the 120-130 range. my 5 liter part euro was in the 155 range, and the holbert S4 with 85 cams is 180 ish.

i wouldnt be so worried about #8, i would be worried about #7 at 135.

I would do the test again. could have had a loose compression tester fitting in the sparkplug hole. full throttle doesnt really matter, as the volume of air moving over time is small enough for the throttle idle hole to feed. however, you can get the max reading in less pumps.

Mk