can loose valve guides
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can loose valve guides

  1. #1
    Senior Member miketeast's Avatar
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    Default can loose valve guides

    make a valve head break off...or a seat fall out?
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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by miketeast View Post
    make a valve head break off...or a seat fall out?
    Mike, with your logical, over analyzing self I'm flabbergasted you're even asking this question.
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  4. #3
    gn7
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    YES. But it could just as easily be something else. A seat ground wack will open up a guide in no time, and knock the seat out, or the head off a valve as well. So which came first, the chicken or the egg? Valve train in a BBC (any engine for that matter) is way more critical than many give it credit for. Screw up a lower end, and you find out real quick. grind a seat f'd up, and you loose an insert maybe 2 seasons later.



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    Quote Originally Posted by miketeast View Post
    make a valve head break off...or a seat fall out?
    Yes, but so can a weak spring especially if its an intake on a BBC

  7. #5
    steelcomp was here
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    Quote Originally Posted by jungledave View Post
    Yes, but so can a weak spring especially if its an intake on a BBC
    X2...youre far more likely to have a seat get beat to death by weak valve springs than bad guides. Likewise with a broken valve. GN7 is also right in saying worn guides are usually a sign or symptom of something else that's wrong, not usually the cause of a problem. At least I think that's what he was saying...he is getting kinda old...

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    Senior Member miketeast's Avatar
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    First and formost thankyous for the response

    this was a 377 10:1 (stock bore 3.75" stroke) SBC (roller block) at the end of it's 4th long season...absorbed two blowers' worth NOS (100-150shot for up to 20 seconds) at a time at a rate of 10lbs/week or better. It spun a B impeller 5500rpm off the gas (450hp) for miles and miles at a time

    The engine had a relatively mild comp xm278hr (i think that was the number) with 1.5 roller rockers lift about .55 at the valve (as i remember)

    The geometry was off, not according to comp, but according to mid-lift...not that far. I have my reasons...


    Dont know what came first, the intake valve or the seat, but the seat distributed itself equaly thru the single plane intake to destroy the heads and 4 pistons.

    Upon dissassembly it was found some of the valve guides were appalingly worn...in a different pattern than i would expect. Usually they wear left to right... some were open all the way around...the one that broke was one of the least worn. I have not checked the springs, but i have their original specs. They were nothing special or expensive.

    No piston contact indicating valve interference from overrev or lofting was seen.

    The valve seats (the 15 left) did not look hammered.

    No bad rockers or bent pushrods.

    This engine survived several big blocks...and kept up....i pushed it as hard as i could. It did its time.

    It can go 30 over. I MIGHT be able to just put some new pistons/bearings in it. It has a scratch on a cylinder that i dont know can be gotten out with a hone....i have not really looked at the shortblock yet.

    If bearings/std pistons/rings will do it...back it goes...if not 421 sbc 3.85stroke goes in.

    again, thanks for the response...i have taken pics but have not taken the time to post them, yet. I will try to get closeups of the seats and guides...
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  9. #7
    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by miketeast View Post
    ... It has a scratch on a cylinder that i dont know can be gotten out with a hone...
    ...
    A can of (well shaken) Engine RESTORE is you friend.
    GN7 made me post this
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  10. #8
    gn7
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    Quote Originally Posted by HammerDown View Post
    A can of (well shaken) Engine RESTORE is you friend.
    GN7 made me post this
    Laugh all you want It may be rings in a can, but it sure as hell isn't cylinder in a can.



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    gn7
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    Quote Originally Posted by miketeast View Post
    First and formost thankyous for the response

    this was a 377 10:1 (stock bore 3.75" stroke) SBC (roller block) at the end of it's 4th long season...absorbed two blowers' worth NOS (100-150shot for up to 20 seconds) at a time at a rate of 10lbs/week or better. It spun a B impeller 5500rpm off the gas (450hp) for miles and miles at a time
    You don't say if this was a intake or an exhaust. But it was an exhaust, you think maybe you should have seen this coming.



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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by gn7 View Post
    Laugh all you want It may be rings in a can, but it sure as hell isn't cylinder in a can.
    Or in my situation > carb in a can
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    Senior Member wagspe208's Avatar
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    Did a seat actually fall out, or just the question?
    A seat falling out could sure cause a valve head to break off. I just bend em, though. LOL
    Wags

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    Senior Member miketeast's Avatar
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    Quote Originally Posted by gn7 View Post
    You don't say if this was a intake or an exhaust. But it was an exhaust, you think maybe you should have seen this coming.
    it was an intake valve. No tulip or anything seen on the exhaust valves (maybe i dont know what to look for)


    taking this block to 600hp (6150rpm on a b) is shakey at best, i know....it held oil pressure with 0-40 oil at 40psi idle at 180F on a standard $15 oil pump.

    I am very interested in the bearings and rods...it was a 4130 crank and 4340 beam rods. I would press 100shot on 89octane at 34deg....get 130hp out of it...but only on 89...not 93...

    It was a light powerplant...i felt it worked wonders on the cheyenne...made it a very enjoyable boat.
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  15. #13
    Senior Member miketeast's Avatar
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    Quote Originally Posted by HammerDown View Post
    Mike, with your logical, over analyzing self I'm flabbergasted you're even asking this question.
    this has nothing to do with the Engine/Jetdrive system. It has to do with engines and i am a rookie in this respect...

    the entities that responded understand the strain that the jetdrive puts on an engine....

    they have seen the insides of hundredes of engines...and have probably seen the results of mistakes made than i have time left here on this earth to experience if i started today and did it 24/7... they might even think in terms of centistokes...

    they speak in the language of torque, it takes some conversion, but i get it... although when i hear about the 'shop dyno' i laugh...i got one bolted to my engine...it dont lie...it is never 'happy'.

    Factobidness i just did some calculations on my dream 421...using formulae proven over some years (ax Soaker)

    I should get 520hp (spin a B at some ~5800rpm)...89 octane...and be able to spray 150 (93 octane) over that...until the bottle runs out...that is ~6300rpm

    while this aint to many rpm for a small block (so they say)...the strain goes up as the fouth root of the RPM and by switching to an A impeller (6000rpm on the spray) i loose a little HP (.05), but knock out better than a fifth of the strain (.82 the amount of strain).

    i was certainly hesitant to ask anything here...but am delighted at the response...informative, professional and appreciated if not heeded.
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  16. #14
    gn7
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    Quote Originally Posted by miketeast View Post
    I would press 100shot on 89octane at 34deg....get 130hp out of it...but only on 89...not 93...
    .
    Quote Originally Posted by miketeast View Post
    First and formost thankyous for the response

    this was a 377 10:1 (stock bore 3.75" stroke) SBC (roller block) at the end of it's 4th long season...absorbed two blowers' worth NOS (100-150shot for up to 20 seconds) at a time at a rate of 10lbs/week or better.
    Oh Mike, one other thing that will kick a valve seat loose.
















    DETONATION!!!!
    I know, it never detonated. You were listening



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    Last edited by gn7; 09-14-2010 at 07:10 PM.

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