Blow By... Front main blown again.

DAVe3283

DAVe3283

Heavy & Slow
Sep 3, 2009
3,727
296
83
Boise, ID, USA
So much off topic on the oil here. We all seem to agree that the level of blowby isn't caused by the oil, so we should check other things.

I am interested to see what the compression & leakdown test results show.

The fact that it is mainly coming out one side does imply a problem with the head (pushed injector, bad valve guide/seals, cracked intake/exhaust runner). If the compression & leakdown tests look good, it might be worth pulling that valve cover and looking for issues. Pressurize the intake & exhaust to 30 PSI or so, and see if air comes out anywhere.
 
DMAX497

DMAX497

New member
Sep 27, 2012
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That's the plan for Thursday...

Motor is an lml block that only had 3k miles on it. Motor was tourqe honed the works...
 
DMAX497

DMAX497

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Sep 27, 2012
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Everything is good... Pistons have valve reliefs etc...
 

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Burn Down

Burn Down

Hotrodder
Sep 14, 2008
7,092
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Boise Idaho
Chevy1925 said:
Your extremely low on compression in those tests. Was that on a warm engine or cold?

Warm, you should be min 380-390 or more.
Click to expand...

Also need to know how he did the test. Full charge on battery, glow plugs all out or???

I just tested a 219,000 mile LB7 410-425 psi all 8, cold engine, all glow plugs removed, full charge on the batteries.
 
DMAX497

DMAX497

New member
Sep 27, 2012
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Cold engine. All glow plugs out. Full charge battery ( batteries are a month old ) with battery charger hooked up.

Same short block motor as mine in another truck lb7 was netting same compression results on cold motor. Same piston. Same comp ratio. Same everything short block wise. Pushed no oil.

Leak down test was done right after. All glow plugs removed.
 
Burn Down

Burn Down

Hotrodder
Sep 14, 2008
7,092
28
48
Boise Idaho
Ne-max said:
15:5-1 on Mine. Compression is at around 325 on all 8.
Click to expand...

DMAX497 said:
Cold engine. All glow plugs out. Full charge battery ( batteries are a month old ) with battery charger hooked up.

Same short block motor as mine in another truck lb7 was netting same compression results on cold motor. Same piston. Same comp ratio. Same everything short block wise. Pushed no oil.

Leak down test was done right after. All glow plugs removed.
Click to expand...

Both of you are running monster cams correct?
 
DMAX497

DMAX497

New member
Sep 27, 2012
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Utah
Thinking our plan...

Ordering SoCal flat valve covers. Welding extra bungs on them. Running to catch can. Then through the hood stack.

Seen several set ups like this on cummins...

My set up runs about 85lbs of boost overall.
 
Harbin_22

Harbin_22

Active member
Dec 4, 2010
3,858
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Southern Indiana
I have the Vibrant Evac exhaust PCV fittings on mine and they are working like a champ. I put catch cans on and within 500miles one of my 69's were pushing oil on the compressor side, just normal driving. Put these in and haven't had a problem since. I put a gauge on the crankcase and at 80-85#'s boost, it was showing 1-2psi positive pressure. Been meaning to put catch cans back on and see what it reads.
 
TheBac

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
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Mid Michigan
I cant quite make out all the figures, but is that 5 on the leakdown test except for #8, which was 10? And is #8 also the lowest compression cylinder? If so, maybe you should be checking a bit further.
 
DMAX497

DMAX497

New member
Sep 27, 2012
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Utah
#6 was the lowest compression cylinder. Write down error lol. #8 is supposed to be number 7 which was more so closer to 10%...

Sorry #8 on the lead down that is a 5.
 
DMAX497

DMAX497

New member
Sep 27, 2012
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Utah
Ordered so cal valve covers. Going to have four breathers total. Into the catch cans. And from the catch cans to two hoses into the exhaust.
 
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