What do these engine measurements indicate.

[Vanhack]

Hi folks this is my first post, Just bought a 4.0 manual 2006 TJ. The jeep has had it''s original engine replaced from a desert rally TJ, but previous owner is not sure of any mods to the engine.

I have been measuring the vacuum on this engine and record vacuum at 17.8 to 18.1 inhg. I am using a vacuum gauge connected to the vacuum line on the brake booster vaccum hose and used the hvac vent controls port. From this I suspected piston rings worn, so did a compression test.

These are my compression readings,

1 155ps
2 165psi
3 155psi
4 167psi
5 163psi
6 160psi

Readings are above the factory spec of 150psi max, but within the variation range between cylinders. Is my engine modified from factory. The vacuum should be above 20-22 inhg right?

[SkylinesSuck]

Was your throttle body propped open when you ran the test? Hot or cold motor?

[Vanhack]

Throttle fully open, cold engine

[Vanhack]

Anyone?

[jsawduste]

Elevation ? That does play a bit in numbers.

Assuming relative sea level there is likely a small cam in it. "From the Factory" is meaningless without knowing what "Factory" your talking about. An engine setup for JeepSpeed would likely have been cammed a little to boost power, yes.

If you have good oil pressure and no abnormal noise than run till it doesn't have oil anymore or starts making expensive noises.