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How to get rings to seat in a rebuilt engine?
#1366272 Wed Jun 24 2020 07:02 PM
Joined: Sep 2011
Posts: 1,977
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Lugnutz Offline OP
Shop Shark
There seems to be a good bit of blow by in a freshly rebuilt 2003 Silverado 5.3 engine. It has zero miles. Oil is accumulating inside the intake and further investigation will likely prove its coming up through the PCV system.

The engine has maybe 20 minutes of run stand time so far, all done in 2-5 minutes segments. No funny knocks.

What tricks or methods are used to get the new rings to seal?
I’m waiting on a leak down test tool but I expect any serious lack of compression I find will be blamed on rings that aren’t sealed. Either that or the rebuild wasn’t done properly.

Last edited by Lugnutz; Wed Jun 24 2020 07:03 PM.
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366285 Wed Jun 24 2020 08:32 PM
Joined: Feb 2001
Posts: 1,110
D
Shop Shark
Seems pretty obvious to me that your 2 -5 mins of cold running 8 or 10 times has done NOTHING to help run the engine in .

Cold start is the most damaging moment for any engine .

Get it out on the road and drive it like you stole it .

For hours .........

Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366291 Wed Jun 24 2020 09:03 PM
Joined: Feb 2004
Posts: 20,564
H
Boltergeist
10 full throttle accelerations from 30 to 50 MPH used to be the rule of thumb back before the days of automatic transmissions that would downshift if pushed hard. Now, I'd suggest finding a hill that allows you to make a long pull without a kickdown, and run it repeatedly. There are several shade tree procedures that involve running a slurry of abrasive such as Bon Ami cleanser and lightweight oil down the carburetor to seat rings, but I've never seen it dome with much success.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366307 Wed Jun 24 2020 09:45 PM
Joined: Sep 2011
Posts: 1,977
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Lugnutz Offline OP
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Thanks for the replies. The engine is on a run stand. It will get more tests. I did not rebuild the engine, so rather than put complete faith in the builder, the engine will go through more run time and see what happens. Right now there is a lot of oil accumulating inside the intake. A LOT! I wouldn’t put this engine in a vehicle until it passed all tests and I was convinced the oil coming into the intake would correct itself.

I’m gonna use a catch can to prove the theory the oil is coming through the PCV line. That, and I’m getting 2 different oil pressure readings from different locations. I might have a bad sensor. I’m gonna switch to a different gauge and use a capillary style sensor.

Last edited by Lugnutz; Wed Jun 24 2020 09:51 PM.
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366356 Thu Jun 25 2020 03:24 AM
Joined: Sep 2011
Posts: 710
B
Shop Shark
Do you know what year the engine is, possibly RPO?


BC
1960 Chevy C10 driver 235 T5 3.73 dana 44
1949 GMC 250 project in waiting
1960 C60 pasture art
G.M dealer tech since 1980 & counting
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366359 Thu Jun 25 2020 03:32 AM
Joined: Sep 2011
Posts: 1,977
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Lugnutz Offline OP
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This is a 2003 LM7 (LS based) engine. Stock rebuild.

Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366366 Thu Jun 25 2020 04:48 AM
Joined: Feb 2004
Posts: 20,564
H
Boltergeist
All it takes to do a cylinder leak test is an air pressure source, a pressure regulator, and a spark plug. File, grind, or machine away the crimp where the porcelain is crimped into the plug shell, knock the porcelain out, and weld or braze an air line quick coupler to the plug shell. Use vise grips or something similar to lock the flywheel as each cylinder comes to the top of the compression stroke, and use the modified plug and air line to apply pressure to the cylinder. Listen at the intake, exhaust, and oil fill for air leaks. If you set the air pressure to 100 PSI with no air flowing, the pressure that each cylinder holds will indicate the percentage of leakage. For instance- - - -88 PSI with air applied to the cylinder will indicate a 12% leakdown rate. Any more than 2%-3% leakage will be too much for a new engine, even if the rings aren't fully seated.

Have you tried running the engine with the PCV system plugged off to see if the oil residue in the manifold is reduced, or stops happening? Are you getting heavy blue smoke from the exhaust?
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366369 Thu Jun 25 2020 05:09 AM
Joined: Sep 2011
Posts: 710
B
Shop Shark
I`It all dig a little when I get to work. Couple things comes to mind, wrong or damaged L.H. valve cover, wrong PCV valve, pcv valve o-ring missing or damaged. Other than excessive cylinder leakage, aka blow-by.


BC
1960 Chevy C10 driver 235 T5 3.73 dana 44
1949 GMC 250 project in waiting
1960 C60 pasture art
G.M dealer tech since 1980 & counting
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366377 Thu Jun 25 2020 11:54 AM
Joined: Sep 2011
Posts: 1,977
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Lugnutz Offline OP
Shop Shark
This engine has a PCV system built into the VC. Nothing to replace. Air has free flow in both directions. I wasted a few good hours trying to understand why MY PCV wasn’t like the ones in the YouTube videos. Haha!
I’ll use a catch can to prove or disprove that the PCV is involved in bringing oil to the intake.
Here are a few pictures for your entertainment. The dark picture shows a layer of oil settled to the bottom of the intake. There's enough oil that you can see a reflection of the hole at the back of the intake. You are looking down the throat of the throttle body. On start up I get a tremendous cloud of smoke which clears. the compression check numbers indicate the cylinders are wet with oil. The plugs are all wet except for #2. The brand new oil is charcoal black from blow by (I presume).
The engine runs but the aftermarket computer has not had enough time to “learn” yet, so it’s not running well.

Attached Files
2E29C353-0186-458A-8A46-6FDDB6676268.jpeg (146.54 KB, 141 downloads)
E74A1705-07CA-4D58-86EC-599BD1F4406F.jpeg (116.51 KB, 143 downloads)
AEBD0072-8986-48FC-8210-0A002E194E20.jpeg (324.91 KB, 140 downloads)
Last edited by Lugnutz; Thu Jun 25 2020 01:11 PM.
Re: How to get rings to seat in a rebuilt engine?
Lugnutz #1366397 Thu Jun 25 2020 02:00 PM
Joined: Sep 2013
Posts: 1,028
M
Shop Shark
Good advice above for sure. One must however never overlook a chance to acquire more cool tools and this is a good one. A wireless endoscope or bore scope would let you look into the cylinders (after only pulling spark plugs) and inspect the cylinder walls and piston tops. I'd be looking at cylinder wall finish for proper crosshatch pattern and anything else obviously amiss. Among the amiss items would be scratches in the cylinder wall from a ring broken on installation, one cylinder (or more) with oil or burned oil deposits on the piston top. I'd expect the combustion chamber to be pretty pristine on a new rebuild.

The endoscope I mention in this thread, isn't available on Amazon currently but they have many in the sub $50 price range. I highly recommend picking one up and looking into your problem engine.

Good Luck

RonR

Last edited by moparguy; Thu Jun 25 2020 02:32 PM.

1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



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