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What do these engine measurements indicate.

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Vanhack
Posts: 3
Joined: June 16th, 2017, 12:50 pm
Vehicle Year: 2006
Vehicle Make: Jeep
Vehicle Model: Tj

What do these engine measurements indicate.

Post by Vanhack » June 16th, 2017, 5:56 pm

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?

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SkylinesSuck
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Posts: 361
Joined: February 14th, 2009, 11:11 pm
Stroker Displacement: 4.6L
Vehicle Year: 1998
Vehicle Make: Jeep
Vehicle Model: Wrangler
Location: Northern VA

Re: What do these engine measurements indicate.

Post by SkylinesSuck » June 17th, 2017, 5:32 am

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

Vanhack
Posts: 3
Joined: June 16th, 2017, 12:50 pm
Vehicle Year: 2006
Vehicle Make: Jeep
Vehicle Model: Tj

Re: What do these engine measurements indicate.

Post by Vanhack » June 17th, 2017, 6:58 pm

Throttle fully open, cold engine

Vanhack
Posts: 3
Joined: June 16th, 2017, 12:50 pm
Vehicle Year: 2006
Vehicle Make: Jeep
Vehicle Model: Tj

Re: What do these engine measurements indicate.

Post by Vanhack » June 21st, 2017, 2:51 am

Anyone?

jsawduste
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Posts: 962
Joined: February 28th, 2008, 3:13 am
Stroker Displacement: 4.9
Location: Michigan

Re: What do these engine measurements indicate.

Post by jsawduste » June 21st, 2017, 5:17 am

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.

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