Compression left bank to right bank diff?

[Young1]

Decided to put new plugs in my 50,000 miles Z today so did compression check also.
Left bank 240,240,240,245
Right bank 255,250,258,260
Why is the right noticeably higher? Cam timing? Machine error? Gasket thickness?

[Ccmano]

Originally Posted by Young1

Decided to put new plugs in my 50,000 miles Z today so did compression check also.
Left bank 240,240,240,245
Right bank 255,250,258,260
Why is the right noticeably higher? Cam timing? Machine error? Gasket thickness?

While any of those things could cause the left-right issue, I suspect something is wrong with your tester. Unless the car has been modified, your readings are excessively high. Normal, sea level readings should be ~210 to 220psi. Try a different compression gauge and see what happens. I’ve run into more than one gauge that was bad.
H

[Paul Workman]

I concur with Hans.

FYI:

• My stock compression average was in the 195± a point or two.
• After Pete phased the cams as part of my porting and headers upgrade, my compression centers around 220#.
  
• Pete and others who have phased the LT5 cams have mentioned that it is not unusual for the cam chain sprocket to slip a tad which results in a situation very similar to what you've described.
  
• Your gauge may be at fault, OR two, it is "SOP" to have a battery charger bring the battery to full charge before doing the testing AND during the testing to keep the battery at full charge between cylinder tests - which you may already be doing - just sayin.

I'm suspicious too, regarding your gauge. But, I wouldn't be too concerned about it - especially if you have an upgrade in your plans: the phasing can be addressed then.

[Young1]

Thank you gentlemen. Car is stock. Battery was well charged and 5 months old but I did not have a charger on it during tests. No mods in the future. I shall continue to drive and enjoy.