I have been doing my compression test every year,since I've had the car. I got the car back in 2007, since then it has been turbocharged almost 2 years and now it has been supercharged for the past 3 years. The first time I ever did the compression test it was high 190's across the board. Last year compression test was high 180's and now I just did one and got 184,171,170,170. The car has 148k miles. It seems that I'll be needing to be rebuilding soon.... at what compression would I need to start worrying about replacing the engine?

 

Have you adjusted the valves?

 

Last time it got adjusted was at 100k

 

Common sense dictates that your compression numbers are probably fine because they are all *consistent* ... but a lot of the armchair mechanics on here will tell you your engine is about to die because you aren't blowing 240/240/240/240 on all cylinders. The largest variance between 170 and 184 is 14psi (or only 8.2%).

Helms manual:

• Nominal: 228 psi
• Min: 135psi
• Max variation: 28psi

Perhaps try using another compression tester, make sure:

• Engine at operating temp (hot)
• Pull all spark plugs out
• WOT
• crank each cylinder the same amount (5-7 times)
• Injectors unplugged