Compression left bank to right bank diff? - ZR-1 Net Registry Forums

Young1 · 12-16-2018

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 · 12-17-2018

Quote:

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 · 12-18-2018

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 · 12-19-2018

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.

12-16-2018	#1
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 900	Compression left bank to right bank diff? 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? __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

12-18-2018	#3
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Compression left bank to right bank diff? 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. __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry

12-19-2018	#4
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 900	Re: Compression left bank to right bank diff? 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. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.