Dakota compression test results

[70charginglizard]

Well the good news is that I'm getting and exactly 170 psi across cylinder 1-7
The bad news is that cylinder no. 8 is only pushing out 150 psi.

Now the big question of the day.

Is there anything I can really do about it besides ripping the whole engine apart and putting in new rings.

I AM NOT HAPPY   

[firefighter3931]

That's not really a huge difference. Kelly, try squirting some oil into the cylinder to see if the reading comes up. If the wet test shows an increase then the problem is ring related. If there's no change, then it's the valves. Try to isolate the problem before doing anything....that's my advice. 

Ron

[rt green]

well said

[Plumcrazy]

I wouldn't worry about it, I'd be amazed if they were all exactly the same. 

Chrysler had problems in the 90's keeping the compression ratio consistant in the magnum engines.  Some would really ping on regular unleaded while other ones would run just fine on it.

[70charginglizard]

That's not really a huge difference. Kelly, try squirting some oil into the cylinder to see if the reading comes up. If the wet test shows an increase then the problem is ring related. If there's no change, then it's the valves. Try to isolate the problem before doing anything....that's my advice. 

Ron

How much oil do you put down there?

[firefighter3931]

About an eye droppers worth should do it. 

Ron

[70charginglizard]

It went up 2 PSI 


checked it twice

[firefighter3931]

Well, the good news is that it's not the rings.  If you want to see if the valves are leaking you'll have to do a leakdown test with the valves closed. This bsicly involves pressurizing the cylinder with the rocker arms backed off. The leakdown tester is attached to a compresser and there is a guage that allows you to monitor the amount of pressure that remains or leaks out of the cylinder over a given period of time. At 5-8% leakage i wouldn't be too concerned about it.

Actually, a 20 psi deviation from best to worst really wouldn't concern me all that much either. See Plum's post above re: later magnum engines.


Ron

[Chryco Psycho]

15% is about where I would start to worry
run it

[70charginglizard]

Doesn't make you wonder though. With 170 psi across every cylinder except for no. 8

Something must be going on mechanically. I'd still like to know what.

[rt green]

still, 170 is very good. wouldnt worry