401 Started Smoking

Discussion in ''Da Nailhead' started by Kqqlcat, Jun 22, 2017.

  1. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Vacuum gauge, get a vacuum gauge!
    It'll tell you all you want to know without doing potentially expensive or time consuming exploratory surgery!
    Put it on manifold vacuum (constant) and then see what the needle is doing. You can probably pull off a chart online on how to read it. Believe me, it's well worth the $10 expenditure.
     
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  2. Kqqlcat

    Kqqlcat Well-Known Member

    I'll try that next. where can I get a chuck with spark plug threds?
     
  3. telriv

    telriv Well-Known Member

    The 170 in the "Bad" cylinder is flooded with oil already. To check weather rings or valves you add oil & if the compression numbers come up it's usually worn rings. So what I'm trying to say, if that cylinder had the correct amount of oil in it the compression would be lower than 170.
    just my thoughts.
     
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  4. Kqqlcat

    Kqqlcat Well-Known Member

    I am probably getting ahead of my self here but if I need to rebuild this block and if it needs boring I think I am screwed because it's .060 over already. Right?
    Pat
     
  5. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!


    in my experience constant oil smoke is a ring issue. my 66 sat so long the valve seals were all rock hard and broken and missing. it basically had no valve seals at all. it would use a quart every hundred miles. it only visibly smoked when pulling away from a light. i put valve seals in it and cured the issue.

    have you had any detonation issues lately? pull the oil cap when it is running, if it is puffing lots of smoke you likely have a bad piston or broken ring.
     
  6. wkillgs

    wkillgs Gold Level Contributor

    Buick didn't even put valve seals on these engines until the last year, 1966. And only on the intakes! Not a huge problem on these engines.

    There isn't a lot of oil in the head gasket. One feed hole at the front, and a matching hole in the rear of the head that dead heads into the block. Sometimes oil works it's way thru the head gasket and leaks, but it's unlikely it'll leak into the cylinder.

    A bad vacuum modulator on the automatic trans could leak atf into the intake manifold via the vacuum hose. Affected cylinders would depend on where the vac hose attaches.

    Did you check the pcv hose and splash shield? Could be pulling oil into the pcv port at the back of the carb. Would likely affect more than one cylinder tho.
     
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  7. Kqqlcat

    Kqqlcat Well-Known Member

    Ok I got the head off and the cylinders look good. The head gasket had a lot of oil around cylinder and also both intake gaskets (metal type) had oil on them not sure how that happens. Head gaskets look different than the ones in my Felpro box. Not steel material but steel rings around cylinder. Based on the material they left on head and block in my opinion it wasn't a good seal.
    I did check the modulator and PVC first and all good there.
    Pat
     
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  8. Kqqlcat

    Kqqlcat Well-Known Member

    After talking to Russ Martin I ordered iron valve guides, seals and stainless valves. Will have heads redone because he was pretty sure the guides were bad.
    Pat
     
  9. gsgtx

    gsgtx Silver Level contributor

    why new valves ?
     
  10. Kqqlcat

    Kqqlcat Well-Known Member

    Just because I am having the heads gone thru at the machine shop.
    Pat
     
  11. gsgtx

    gsgtx Silver Level contributor

    his valves weigh more then stock valves , are you getting new valve springs ? you will have a heavy valve on a weaker used valve spring.
     
  12. telriv

    telriv Well-Known Member

    1st. off it would be helpful if we knew yr. & engine size & if it's the original engine for your vehicle. Just my opinion here, but I think you may have jumped the gun BEFORE doing a thorough diagnosis. Vacuum gauges are cheap. Spending undue time & $$$ not properly diagnosing the problem at hand = undue wasted time & $$$.
    IF the intake gaskets had oil on them the problem is more than likely coming from the intake manifold side. IF everything is OK on the intake side the gaskets should normally have NO oil on them as it ONLY passes fuel & air, NOT OIL . Could be a bad/incorrect PCV valve. You didn't mention if this was happening with a cold or thoroughly warmed up engine or both. Way too much oil getting to the rockers when cold & can't drain back fast enough because when cold the oil is thicker than normal. After it warms & the oil thins it can flow faster. It would be a REAL dis-appointment if after assembled it started having the same problem again shortly thereafter.
    With those Felpro gaskets if they are .050" thick before compressing you will lose approx. .77-1 compression if a 401 or .44-1 compression if a 425. The advertised compression is 10.25-1. The best I've ever measured was 9.75-1 & that's with a piston in the hole at .040". RARE Normally most measure about .055" in the hole so compression will be even less. Meaning you will end up with less than 9-1 & an engine that doesn't perform as well as previously, more than likely 8.7-1 or so give or take. Now you LOST power & the ALL IMPORTANT squish/quench area. VERY FEW take all these things into consideration when performing these kind of repairs. ALSO, if you end up using the Felpro gaskets block the rear oil passage that dead heads at the block in the rear to prevent future oil leaks at the rear of the heads.
    These are just my opinions based on experience.
    Others PLEASE chime in with your thoughts.


    Tom T.
     
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  13. wkillgs

    wkillgs Gold Level Contributor

    Tom has mentioned oil to the rockers can be reduced by putting a restrictor in the feed hole under the front rocker stand.

    Valve guide and valve stem wear can be measured. Best to verify before throwing new parts and money at it!

    Regarding replacing valve guides, there has been mention of the originals not always having the hole centered in the guide.
    Replacing the guide might put the valve slightly off center from the original seat. The valve seat will now have to be cut deeper, sinking the valve.
    Not sure if the non-concentric guides are fact or myth.
    One of the machinists here mentioned steel or iron valve guide liners? Harder than bronze. Would be an alternative to replacing guides.

    I think someone here had a cracked head at a valve guide. That could allow oil in to the intake track as well.
     
  14. telriv

    telriv Well-Known Member

    Yes, true Walt, but the gasket wouldn't get oil on it because it's below the sealing surface. IF the guides are replaced they press out from the bottom to top & installed top to bottom. If done in reverse can crack the head at the guide.
     
  15. wkillgs

    wkillgs Gold Level Contributor

    Check your rocker shaft to ensure both ends have the sealing plugs. If one is missing/leaking bad, you could be dumping too much oil under the valve cover.
    Suppose it could leak out of the valve cover AND (a long shot) into a leaking intake gasket and into the rear cylinder.
    Or the extra oil is going thru the valve guide.
    Pcv is more likely, but you checked that....

    Years ago, one guy here swore his exhaust manifold bolt was leaking oil! Strange stuff happens...
     
  16. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    I hope you did some diagnosing before you yanked the head...

    upon disassembly of the head your machinist can tell you if what the heads need.
     
  17. Kqqlcat

    Kqqlcat Well-Known Member

    I did check vacuum an it was steady and at 19", PVC is fine, not Felpro gaskets, it was was warmed up 185 degrees, after taking intake off I could see oil around intake valves. It was not smoking very bad just a little how ever who wants to go to a car show when your puffing smoke no matter how little.
     
    Last edited: Jul 6, 2017
  18. Kqqlcat

    Kqqlcat Well-Known Member

    They weigh more? Are you saying Russ doesn't know what he is selling?
     
  19. Kqqlcat

    Kqqlcat Well-Known Member

    Good to know. Not every machine shop has worked on a 401 nailhead.
     
  20. 8ad-f85

    8ad-f85 Well-Known Member

    I don't think it was inferred anywhere that he doesn't know what he's selling.
    Before anyone questions the weight of the valves, I'd assume his valve springs are designed to work with his valves.
    The comment was intended to question the use of weak, worn, stock springs.
     

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