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Low end knock question

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  #21  
Old 01-02-2012, 01:16 PM
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Assuming you did the test right, save up for a new or used motor.
 
  #22  
Old 01-02-2012, 01:54 PM
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Originally Posted by zman17
Assuming you did the test right, save up for a new or used motor.

Gotta agree with this assessment. Those numbers are WAY to low. Time for a new motor, or a rebuild.
 
  #23  
Old 01-02-2012, 02:11 PM
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I checked it with the engine cold...is that going to make a big difference? Also, I bought a leak down tester and used the end hose(spark plug side) with a normal air gauge that I have to check compression. Does an actual "compression gauge" do anything differently? The gauge I had already had a bleed of on it, so I plugged it into the end hose and figured psi is psi....?
 
  #24  
Old 01-02-2012, 02:21 PM
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Go rent or buy a gauge dude... Make an expensive decision based on solid facts.. matter of fact, do the test, write down results, do it again and only settle when you have consistent numbers.. furthermore, if you have any doubts at all- have someone do the test independently from your own, and compare numbers..

I don't mean to sound harsh at all, but if you lack any confidence whatsoever, its better (and cheaper) to get a second independent opinion.. ya know?

You need to find consistent numbers before you declare its engine time.. I'd personally figure numbers within 3psi consistent..
 
  #25  
Old 01-02-2012, 02:35 PM
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Out of curiousity, what is the "recommended" numbers for compression. I believe there supposed to be 120-130 psi, correct?

Reason I ask is:

1) it's on the subject
2) it'll help the OP
3) I did a quick comp. test a few days ago, came up with 118-135 for all 8 cylinders and I tried searching for the "normal" psi but came up empty.
 
  #26  
Old 01-02-2012, 03:20 PM
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Dodge says anything over 100 is 'acceptable'. On a motor with over 100K miles, I would tend to agree.

There shouldn't be more than a 25% difference between the highest, and the lowest either. (again, according to dodge, to me, that seems like a REALLY wide gap....)

There shouldn't be a major change in numbers from dry to wet either. (indicates rings are bad.)
 
  #27  
Old 01-02-2012, 03:26 PM
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well, chalk one up to me being a cheap dumbarse. Apparently you cant use a pressure gauge as a compression gauge. I ran down to Advance and bought a compression gauge and it looked more like this...

#1 - 170
#2 - 165
#3 - 180
#4 - 180
#5 - 180
#6 - 160

Now I feel better about dropping the pan and checking out those bearings. Didn't wanna waste to time if I wasn't making good compression. Whew, that almost cost me ~$700.

Thanks to Drewactual for pointing out that I needed to get my head outta my butt and use reliable test equipment. Drew, looks like you're right up the road in CC too...I'm in Hubert/Swansboro area.
 
  #28  
Old 01-02-2012, 03:27 PM
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MUCH better numbers. THAT is an engine worth saving.
 
  #29  
Old 01-02-2012, 03:40 PM
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Originally Posted by Tparkin
well, chalk one up to me being a cheap dumbarse. Apparently you cant use a pressure gauge as a compression gauge. I ran down to Advance and bought a compression gauge and it looked more like this...

#1 - 170
#2 - 165
#3 - 180
#4 - 180
#5 - 180
#6 - 160

Now I feel better about dropping the pan and checking out those bearings. Didn't wanna waste to time if I wasn't making good compression. Whew, that almost cost me ~$700.

Thanks to Drewactual for pointing out that I needed to get my head outta my butt and use reliable test equipment. Drew, looks like you're right up the road in CC too...I'm in Hubert/Swansboro area.
Are those numbers from a wet or dry test?
 
  #30  
Old 01-02-2012, 03:43 PM
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I better get my fanny to advanced before they are suddenly short of bearings.. I've got a leaking rear main seal, and figured I'd go ahead and go with new oil pump and pick-up at same time too..

I've been known to step out of line here, and I may be doing that now... But... With those numbers you have, and since you're going in there anyway, I'd almost rec against a high flow or high volume oil pump.. you're going to need that oil in the pan and not topside with new bearings and compression numbers like that.. it indicates the engine is still nice and tight, I'd hate to see you run the bearings dry because too much oil is in the galley or atop the heads, ya know?
 


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