1981 Camaro Z28 350 SBC Engine issues.

Discussion in 'Troubleshooting & Diagnosis' started by HB_81Z28_80870, Aug 1, 2020.

  1. rocket dawg

    rocket dawg Veteran Member

    Messages:
    381
    Likes Received:
    45
    Joined:
    May 5, 2015
    Location:
    Grand Rapids Mi
    Actually my 406 oil burner's plugs looked exactly like that going thru a quart every 100 miles. The 170 psi reading is probably enhanced by the extra oil in the cylinders. ( just a guess) My bet is on the intake not making a good seal with the heads. Maybe the deck was machined and the heads/ intake angle is out of whack.
     
    Kimbal Mackinnon likes this.
  2. Kimbal Mackinnon

    Kimbal Mackinnon New Member

    Messages:
    4
    Likes Received:
    1
    Joined:
    Apr 6, 2017
    Wonder why almost nobody is talking about ring seal. "Freshly rebuilt engine" means nothing if it either wasn't set up correctly or not broken in properly. The benefit of the doubt should go to the proper break in procedure/accessories assembly because that's easier to do than correctly assemble a long block. Don't discount the possibilities.

    Burning oil from worn valve guides/seals/PCV typically (from my experience) would yield a wet and oily spark plug with visible (if not obvious) fouling whereas from the rings it would look more of a crystallized buildup on the plug/ piston head and combustion chamber. My LS setup with pistons too small for the hole (and ring flutter :3) had plug buildup nearly identical to the pics posted. That setup went thru a quart of oil every ~1000 miles before I built the bottom end. My worn guide/seal experience is from a 327 in an impala I owned that went thru a quart and a half of oil per week when i daily'ed it to school.
     
  3. COPO

    COPO Veteran Member Lifetime Gold Member

    Messages:
    19,450
    Likes Received:
    1,558
    Joined:
    Sep 15, 1999
    Location:
    Ontario, Canada
    If the cyl walls had a plateau finish then the rings would have a quick break-in.
     
  4. Jodi

    Jodi Veteran Member

    Messages:
    473
    Likes Received:
    259
    Joined:
    May 22, 2019
    IMHO... The spark plug doesn't care where the oil is entering the CC from... whether from below or above, it would show the same symptom.

    This the reason why you have to choose your machine shop wisely... don't always go for the Fancy Equipped shops, remember it's the person that is operating that machine that counts. Even then... double check their work, measuring tools needed to be calibrated...when was theirs done. Was the cylinder honed with a plate? was the plate Torqued properly simulating installed cylinder heads. Cylinder walls could never retain that oil film if the cross hatch pattern is not properly done and if the cylinder is not within specs. to begin with and no amount of proper break in procedure will help.
     
    G72Zed likes this.
  5. G72Zed

    G72Zed Veteran Member

    Messages:
    1,933
    Likes Received:
    774
    Joined:
    Sep 8, 2015
    Location:
    Canada
    I have purposely mentioned this in post #14, 22 & 33.

    X2 on what Jodi said here ^^^^

    And the good machinist/engine builders would sonic check the block before you go dumping $$ into it to make more HP, and not waste their time on a "thin" block. At the shop the other day, a 6.1 Hemi G3 got done, 15 minutes, and the build plan changed on the spot.

    The Pro's would then ask what HG are you going to use composition or MLS, bolts or studs, and if it's and Iron or aluminum head application cause there's both materials for the BHJ deck plates.

    Getting fussy here, but it all adds up. I have seen good money in parts and top machine work in an unchecked block, the more power it made, the worse it got...
     
    Jodi likes this.
  6. HB_81Z28_80870

    HB_81Z28_80870 New Member

    Messages:
    12
    Likes Received:
    9
    Joined:
    Sep 1, 2019
    Location:
    Grimsby On Canada
    Ok boys! I finally received an answer on what happened. Seems that with wrong timing set up twice,too much gas was entering the chamber at the wrong time. Cylinder wash wasn't a problem, but the piston would come up at 1/3 of the stroke & would wiggle due to wrong explosion time. After a while the piston would wiggle enough to allow oil to get above the rings into the combustion chamber therefore the oil blowing by out the exhaust. I had collapsed rod bearings & 2 main bearings smaller than normal apparent that they dropped out on disassemble . #7 cylinder also was down to 25 thou from 30 thou, so that was changed.
    I did see a race mechanic sanctioned by the builders & he said that the carb was good, but needed to go back stock, I left the distributor with him & he blue printed it for my application.

    Kimball Mackinnon you were dead on with the rings shifting as the pistons wiggled in the bore from wrong timing.

    G72Zed - I am taking your advice & am sending it to the race mechanic to have it dynoed & set up for my carb & distributor, so when it's all said & done I am installing the engine & go.

    Worked out a deal with the shop that I only pay for parts ($300 CDN) & they would suck up the labour to clean & reassemble. Still need to pay for Dyno, but cheap insurance now that I have pulled it three times. I am seeing the light at the end of the tunnel. Will be picking up motor tomorrow fully assembled & painted GM corporate blue. Then off to Dyno shop the following week.

    Thanks for all the comments,thoughts & theories, much appreciated,will post something after I've fired it again.
     
    maddog1949 likes this.
  7. COPO

    COPO Veteran Member Lifetime Gold Member

    Messages:
    19,450
    Likes Received:
    1,558
    Joined:
    Sep 15, 1999
    Location:
    Ontario, Canada
    Good to hear.
     
  8. G72Zed

    G72Zed Veteran Member

    Messages:
    1,933
    Likes Received:
    774
    Joined:
    Sep 8, 2015
    Location:
    Canada
    Good to hear this, and please let us know how the break in and dyno testing goes, hope it all works out for you this time around.
     
  9. cadillac_al

    cadillac_al Veteran Member

    Messages:
    920
    Likes Received:
    107
    Joined:
    Apr 22, 2015
    Location:
    Maine
    So this was all caused my not checking TDC? Good tip for future engine builds, don't skip the basics.
     
  10. carhead22000

    carhead22000 oldblue

    Messages:
    69
    Likes Received:
    32
    Joined:
    Sep 5, 2011
    Location:
    canada
    glad to hear your getting up and running.nothing more dissapointing when you pour your heart and soul into your baby.when she fires up next time we want a picture of the smile on your face.good luck brother.
     

Share This Page