I ran a compression test today on the 408. Here's a few pics of the plugs and the compression numbers. Opinions? For those that don't know the background, I've been trying to find the source of the 2 quarts of oil that disappear every 1000 miles.

https://www.performancetrucks.net/fo...d.php?t=384135



Plugs 1-4


Plugs 5-8

 

some motors just use oil...it sucks. my old 6.0 has compression from 170 to 180 and its a 11.1 motor with 50k on it and goes thru oil. new valve seals and etc. i even got rid of the pCV and did the breather setup...only smoke at WOT...

 

#6 looks a little darker but it could be the lighting? Great pics btw.

 

Everything looks fine to me, your compression is good. They arent excessively black so I dont know man. Try a leakdown test it will tell you the true story of what condition your rings are in.

 

How many miles have you put on the motor so far? What kind of oil did you use for break in?
I was talking to one of the guys from SDPC when iwas putting in the order for the rest of my parts. He said within the past couple of years they were having problems with the new motors they were building. He talked to a rep from an oil company who said it has to do with the additives in the oil. he suggested to use Rotella, valvoline NLS racing 10w30, or Pennzoil Racing oil. It had something to do with an additive these have that normal engine oil lacks. Sorry I can't remember. He also suggested using a bottle of GM EOS for break in.

Man, I feel your pain.
I don't know if this information is helpful but I thought I would pass it along. I hope you get it staightened out soon.

plugs don't look bad to me. I double checked my heads to see if 6&8 had anything in common to cause the soot (oil passage). Personally I would have used teflon thread sealer on the rocker bolts, but it sounds like you did a top notch job sealing them as long as you were able to clean the oil residue REAL good.

Good Luck Bro,
Alex

 

After about 3 weeks of a plug change my #5 starts to look like your #6, except mine is really oily. About 2-3 weeks later my #5 is crusted with burnt oil and starts to foul. AND I STILL don't use oil like you. I need to do the leak down test myself. I haven't tried the compression test yet either, but like cody says, a leak down will make you feel alot better.( for better or worse) At least you plugs look real good and compression is pretty spot on.

 

How does the oil look? If you having some blow by by the rings or something like that the oil may look darker than it should. IMO the oil should look brand new, since it has less that 1000k on it and a new build. I agree with what was said above, you gotta do a leak down test to see if the rings are sealing.

You could try pulling the dip stick while it is idleing to see if any vapor is coming out. My last motor in my car had bad rings and it would eat oil, but you could tell cause there was so much blow by threw the PVC and dip stick tube. But that was on a ford, so don't know if they would act the same.

 

did you use a napier second ring?

Rex. the guy who built my motor, has a special ring set that he likes to spec to keep them from being oil burners.

 

Stroker engines typically use more oil as well as forged piston engines since the cyl tollerances are much looser(typicaly .003-.0045" vs .0005-.0015" of cast/hypereutectic pistons). The theory behind the stroker engines oil use is due to the wrist pin moved up higher in the piston and exposing the back side of the oil ring. More oil is avaliable to the oil ring this way thus more leaks by. Also, longer stroke engines pistons rock more at BDC. The greater rod angle, looser piston to bore tollerances, and the fact part of the supporting skirt protrudes down below the sleeve/bore giving less stability at this point; the rocking and partial unloading of tension of the rings causes more oil to leak by.
At least that is what I have read and some of my own ideas thrown it there.

 

bust the ls7 is a gm stroked motor... and as far as I know they don't burn oil