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Robert Meek
Dodge Dakota
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10/07/2002
16:42:51

Subject: Compression on 3.9 liter?
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Hi all,
I have a 3.9 liter 1987 Dakato LE Truck. It has 187,000 miles on the engine. The manuals that I read, state the compression should be 100 PSI. I get 180-185 on all cyclinders. I just got the truck, and thought this high, so I tore the headers off, micro the values, in three places (all were in the high end of specs (like new), and only one had a .001 different in micro values from top and bottom). All the holes for the air pump exhaust vent in the exhaust port, were all carboned up, (like they never were cleared when the heads were done) so I picked them out. The previous owner said, he just had the heads done and I believed that because ,there was very, I mean very little carbon on the intake values and the guides were new and clearances very good. There was some carbon on the top dome (around the spark plug) and it look like it burned oil (with all the half used oil quarts in the truck). OH Yea, there was no RTV Sealer used on the any of the intake manifold gasket! When I put it all back tgether and compressioned check it, it was again 180-185 psi. Are there different heads out there for the 3.9 liter? Does anyone else have the same experience (high compression)? Unless my compression gauge is bad, or the head was shaved (alot), I donn't have a clue. I also replaced the timing chain (as a good little mechanic).



Jon
Dodge Dakota
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10/07/2002
17:53:59

RE: Compression on 3.9 liter?
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How much carbon is on top of the pistons? I've seen carboned up 3.9's pull 230psi on a compression test.

Another though is that when they did the heads they put new rings in it.

-Jon



street guy
Dodge Dakota
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10/12/2002
13:47:30

RE: Compression on 3.9 liter?
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180-185 on an engine in good condition is normal. I would be very concerned if my engine only cranked out 100 psi



Jon
Dodge Dakota
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10/12/2002
22:16:28

RE: Compression on 3.9 liter?
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Yeah 100psi sounds too low, but then again 185 sounds a little high for something with almost 200K on it.

-Jon



cheap oem sof
Dodge Dakota
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2/12/2012
13:49:10

EDPYnoxSNmRBsCuEAF
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EO3Feq Last a few years has been to Ibiza, so met a person there whose style of presentation is very similar to yours. But, unfortunately, that person is too far from the Internet!...



christopher
Dodge Dakota
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1/15/2018
21:38:21

RE: Compression on 3.9 liter?
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what are the compression specs on a 3.9v6 in a 2001 dodge dakota



Mark1998
Dodge Dakota
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3/31/2018
21:29:09

RE: Compression on 3.9 liter?
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How about 135psi on a 3.9 with 200,000 on it.



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