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Exhaust valve or cylinder wall failure?

  1. #29
    Some guy obnoxious001's Avatar
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    Quote Originally Posted by Turboelimtim View Post
    but just rebuilt engine with flattops vs cupped pistons.
    .
    As I mentioned above, you pushed the limits too hard. A 15-1 engine needs better than 110 octane. Did you dyno and get exhaust numbers?

    The one piston I have personally seen that had a perfectly round hole it it showed 1400 degrees exhaust temperature,, the dyno guy should have never left that engine go out the door that way, it was doomed from the beginning.

    I am going to be tied up some the next couple of days, friends from CA out visiting the river. Will call you when I am able, but you need to rethink your combination.

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  3. #30
    Senior Member ol guy's Avatar
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    Quote Originally Posted by SoldHondaBoughtHondo View Post
    Nope....no joke...both heads were like that...and it ran...and it ran ok....i pulled the heads off because local machine shop gave me the wrong rod bearings..they had the crank...from best guess the clearence was .0008 .001...within spec for a mo ho...not for a 427 spinning 6k+ up river for miles..stuck half the rods...think it ran ok because of valve spring pressure 225/520 was gettin the valve back on the seat even if it was crooked...The valve springs ended up being the problem to...junkyard motor i got from a buddy old school roller cam with rev kit..the springs went junk..like way crooked and somebody just shim them to get the number..mean while the crooked spring was sideloading the valve stem and rotating too....Gary Kincaid ended up fixin for me...said those were by far, the worst guides he has ever seen...yes..head had been run,,i just tore it down to clean it up before i took it to gary...i know, you dont believe me....lol you are not the first...call gary..he tell ya..lol...
    I don' call anybody a liar unless I catch them at it. I am not calling anybody for info. It was wrong and that's all I will say. I personally would not put a head on any engine like that. Mark

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    Quote Originally Posted by ol guy View Post
    Everything you have shown still tells me the start of the down fall was a badly stuck valve and the tulip of the valve bouncing around in the cylinder and combustion chamber did the damage. I did not know this was on a fresh rebuild or if you did state it I missed it. My assumption is the valve stuck in the guide, piston hammered the valve until it first bent then broke the valve. You will know that when you hammer the valve stem out of the head and see first it will probably be dry and next it is galled badly and last that it shows alot of heat(partially blued). Keep in touch I want to know what you find. Mark
    Mark,
    Only the bottom end was rebuilt. I've been using these heads for about five seasons with no issues. I also put in a slightly longer duration cam than what was in before. The cam lift is In:.595/Ex:.588. The valve timing, as measured prior to running is IVO 22 deg BTDC IVC 64 deg ABDC, EVO 60 deg BBDC EVC 15 deg ATDC. I'm wondering if the EVO is to early causing exposing the valve to more flame front than before making the exhaust valve run a lot hotter? I have it set 4 deg advance so I could set it 4 deg retarded to have the valve open 8 deg later. I don't doubt that the valve either floated and hit the piston which could have just bent it slightly causing it not to be able to transfer heat into the seat causing the valve to really overheat. I check the intake clearance when putting the motor together , but not sure that I checked the exhaust valve clearance. I'm going to put one of the heads on and measure the exhaust clearance. Here's a pic of the removed stem and head. The stem came out with a light tap and was not bound up in the guide. Of course the guide is a little loose now.
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    Plug pics in order 1-8, 1 is the failed cylinder.
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    Piston tops 2-8 in order. Seems like a lot of carbon for only three trips. Maybe from the PCV plumbed into the carb base.
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  6. #32
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    Quote Originally Posted by obnoxious001 View Post
    As I mentioned above, you pushed the limits too hard. A 15-1 engine needs better than 110 octane. Did you dyno and get exhaust numbers?

    The one piston I have personally seen that had a perfectly round hole it it showed 1400 degrees exhaust temperature,, the dyno guy should have never left that engine go out the door that way, it was doomed from the beginning.

    I am going to be tied up some the next couple of days, friends from CA out visiting the river. Will call you when I am able, but you need to rethink your combination.
    Didn't dyno it, but maybe should this time around. Yeah, I should have run the effective CR number before pushing it too hard. I agree with the idea of going back to 8:25:1. Just hate to buy a complete set of pistons and have 7 barely set of $500 pistons sitting in my garage and re-balance because of new pistons. I have been contemplating going NA, but that's going to be a lot of new hardware (Cam/lifters, exhaust manifolds, etc.) and probably headaches. Guess I'll bite the bullet on the pistons and exhaust valves, and not run too much boost. I would like it to last for a while. When we talk, I'll explain why the rebuild on the short block. Interesting, painful set of circumstances.

  7. #33
    Senior Member Hass828's Avatar
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    You leaned out for whatever reason. Is your water flow through your intercooler stopped up? small piece of garbage can stop up that half closed ball valve. Engine temp-water flow staying nice & cool? Timing? Are the heads aluminum or Iron? Did you get a load of fuel with Ethanol in it? Your new cam might be a problem, it appears there is reversion from exhaust backpressure and overlap. What do the intake ports and intake manifold look like--any signs of intake contamination?
    You cant go off of the "theoretical" comp ratio # and keep it low like suggested. It will be a real turd.
    I have ran these #'s on pump gas for a long time with a 9.4-1 longblock and have never hurt a thing. This chart is from pro-charger which usually isnt quite as efficient as a turbocharged engine.

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    Last edited by Hass828; 06-28-2018 at 10:28 AM.
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  8. #34
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    Quote Originally Posted by Hass828 View Post
    You leaned out for whatever reason. Is your water flow through your intercooler stopped up? small piece of garbage can stop up that half closed ball valve. Engine temp-water flow staying nice & cool? Timing? Are the heads aluminum or Iron? Did you get a load of fuel with Ethanol in it? Your new cam might be a problem, it appears there is reversion from exhaust backpressure and overlap. What do the intake ports and intake manifold look like--any signs of intake contamination?
    You cant go off of the "theoretical" comp ratio # and keep it low like suggested. It will be a real turd.
    I have ran these #'s on pump gas for a long time with a 9.4-1 longblock and have never hurt a thing. This chart is from pro-charger which usually isnt quite as efficient as a turbocharged engine.

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    Thanks for the input Hass. I've followed your build from back in the hotboat days when you were mocking up the exhaust. Awesome setup you put together and obviously you know your stuff. I'm really trying to get to my failure root cause here and I thick there are three possibilities.

    First a quick background. I bought a used short block for a rebuild (needed due to spun bearing, which is an interesting, but not pertinent story all in itself). Decided to go with 9.5 vs. 8.25 CR because I'm already burning 91 octane and it should be a little more responsive. Put a little more duration in the cam (which as you say, could be an issue). The actually measured numbers are IVO/IVC 22 BTDC/64 ABDC (266 dur), EVO/EVC 60 BBDC/15 ATDC (256 dur). Aluminum head w/SS exhaust valves. Draw thru Holley 900, large PFM IC. Measured 11:1 AF last check. Ran on trailer to break in cam for 1/2 hour with hose. Took to lake and ran for about an hour under 4k w/no boost, second trip to lake ran about an hour with a couple of, maybe 15 second WOT runs at 9 psi, 53-5400 rpm. No issues. Took on weekend trip Ran it pretty hard first day, no issues. Ran second day, but easy and only for about 1/2 hour. Third day tooled around lake for about 30 minutes. Took it out for speed run and ran at about 5 psi boost for about 30 seconds. Stopped, let my son drive. He takes off about 4500 to plane, then takes it up to right around 5000, hears a noise (I didn't hear it) and immediately cuts throttle and engine dies. I try to start it and it's locked up.

    Possible causes: 1) my original thought - cylinder wall cracked and sprayed cold water on valve causing it to fail and hole was caused by very hot stem side of broken off valve head (mainly because of the size of the crack). 2) Valve failed due to heat and broke off causing piston and cylinder failure. 3) Detonation caused hole in piston, but not sure how that lead to other failures.

    So my questions are: Is the small hole definitive proof that the failure was initiated by a lean condition in #1 or could the valve failure caused the hole. Could the piston failure cause the valve failure? What caused the cylinder wall failure (I cut through the crack and the wall is about .25 in thick)? What caused the lean condition and is there any evidence of it in other cylinders from the pics? Does the carbon pattern on the "new" pistons look normal? It seems like the center pistons have more build up than the outer ones. I think there may not have been a good head/block seal because of some rust on some plugs indicating water is getting in the combustion chamber. Could this have lead to the failure somehow. I tested the IC for leaks after teardown at not a drop at 50 psi. Here's a pick of the exhaust port and head. There is some kind of residue, which I think is due to water. All intake ports look perfectly clean/normal.
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  9. #35
    Senior Member Hass828's Avatar
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    Quote Originally Posted by Turboelimtim View Post
    Thanks for the input Hass. I've followed your build from back in the hotboat days when you were mocking up the exhaust. Awesome setup you put together and obviously you know your stuff. I'm really trying to get to my failure root cause here and I thick there are three possibilities.

    First a quick background. I bought a used short block for a rebuild (needed due to spun bearing, which is an interesting, but not pertinent story all in itself). Decided to go with 9.5 vs. 8.25 CR because I'm already burning 91 octane and it should be a little more responsive. Put a little more duration in the cam (which as you say, could be an issue). The actually measured numbers are IVO/IVC 22 BTDC/64 ABDC (266 dur), EVO/EVC 60 BBDC/15 ATDC (256 dur). Aluminum head w/SS exhaust valves. Draw thru Holley 900, large PFM IC. Measured 11:1 AF last check. Ran on trailer to break in cam for 1/2 hour with hose. Took to lake and ran for about an hour under 4k w/no boost, second trip to lake ran about an hour with a couple of, maybe 15 second WOT runs at 9 psi, 53-5400 rpm. No issues. Took on weekend trip Ran it pretty hard first day, no issues. Ran second day, but easy and only for about 1/2 hour. Third day tooled around lake for about 30 minutes. Took it out for speed run and ran at about 5 psi boost for about 30 seconds. Stopped, let my son drive. He takes off about 4500 to plane, then takes it up to right around 5000, hears a noise (I didn't hear it) and immediately cuts throttle and engine dies. I try to start it and it's locked up.

    Possible causes: 1) my original thought - cylinder wall cracked and sprayed cold water on valve causing it to fail and hole was caused by very hot stem side of broken off valve head (mainly because of the size of the crack). 2) Valve failed due to heat and broke off causing piston and cylinder failure. 3) Detonation caused hole in piston, but not sure how that lead to other failures.

    So my questions are: Is the small hole definitive proof that the failure was initiated by a lean condition in #1 or could the valve failure caused the hole. Could the piston failure cause the valve failure? What caused the cylinder wall failure (I cut through the crack and the wall is about .25 in thick)? What caused the lean condition and is there any evidence of it in other cylinders from the pics? Does the carbon pattern on the "new" pistons look normal? It seems like the center pistons have more build up than the outer ones. I think there may not have been a good head/block seal because of some rust on some plugs indicating water is getting in the combustion chamber. Could this have lead to the failure somehow. I tested the IC for leaks after teardown at not a drop at 50 psi. Here's a pick of the exhaust port and head. There is some kind of residue, which I think is due to water. All intake ports look perfectly clean/normal.
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    You should be ok with that camshaft-- it is 112lsa and has only 37* of overlap. I dont know how well your fuel curve on those carbs are setup, but when you say that it was ran at 5psi for XX amount of time then it was ran at 9psi for XX amount of time, you might find a throttle position where you are lean. Really need a good 02 sensor on the thing with a warning light so you will not run too lean. I ran a 9-1 BBC with a Banks intercooled draw through @ 18psi with a 325 shot of Nitrous(entire pass) for over 10yrs on sunoco 110, with 28* locked timing. Never could kill the thing.
    "if we keep doing it the same way we always do..we will always get the same results"
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  10. #36
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    Beat on that old Banks deal for over 10yrs with nitrous & boost. It was a tough SOB, and pretty fast for what it was.

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    Pulled short block out of boat onto stand. #1 rod bent laterally (toward crank), rubbing on crank. Managed to get #1 out of black, and other 7. Noticed another vertical crack in #1 cylinder on opposite side of big crack. Also, pulled the slug that came out of the piston out of the oil pan. It is almost exactly the shape of the hole in the piston. It is smooth on one side just like the bottom side of the piston and a little marred up on the other side. Am I wrong to surmise that this slug is an indication that the valve broke off, flipped 180 degrees and punched this hole in the piston with the stub of valve stem that was on the broken off head? The slamming of the valve head also bent the rod and turned the piston (about the pin) in a manner that breached the cylinder wall. I'll post pictures in a bit. My iPhone took a dive this AM.

  12. #38
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    Quote Originally Posted by Turboelimtim View Post
    Pulled short block out of boat onto stand. #1 rod bent laterally (toward crank), rubbing on crank. Managed to get #1 out of black, and other 7. Noticed another vertical crack in #1 cylinder on opposite side of big crack. Also, pulled the slug that came out of the piston out of the oil pan. It is almost exactly the shape of the hole in the piston. It is smooth on one side just like the bottom side of the piston and a little marred up on the other side. Am I wrong to surmise that this slug is an indication that the valve broke off, flipped 180 degrees and punched this hole in the piston with the stub of valve stem that was on the broken off head? The slamming of the valve head also bent the rod and turned the piston (about the pin) in a manner that breached the cylinder wall. I'll post pictures in a bit. My iPhone took a dive this AM.
    Anythings possible. The pic of that hole appears torched, and its a hell of a coincidence that it is right were the heat from the exhaust port was marking all of the pistons.
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  13. #39
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    Quote Originally Posted by Turboelimtim View Post
    Pulled short block out of boat onto stand. #1 rod bent laterally (toward crank), rubbing on crank. Managed to get #1 out of black, and other 7. Noticed another vertical crack in #1 cylinder on opposite side of big crack. Also, pulled the slug that came out of the piston out of the oil pan. It is almost exactly the shape of the hole in the piston. It is smooth on one side just like the bottom side of the piston and a little marred up on the other side. Am I wrong to surmise that this slug is an indication that the valve broke off, flipped 180 degrees and punched this hole in the piston with the stub of valve stem that was on the broken off head? The slamming of the valve head also bent the rod and turned the piston (about the pin) in a manner that breached the cylinder wall. I'll post pictures in a bit. My iPhone took a dive this AM.
    Kinda what I told you in the first place but instead of being stuck it broke or back to what I thought in the first place stuck then broke and did it's damage. But now you bring another factor in with the adjacent cylinder also being cracked. This could lead to a serious cooling issue. One thing to check is if the block is sand packed. Pop the freeze plugs and look? M

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    Quote Originally Posted by ol guy View Post
    Kinda what I told you in the first place but instead of being stuck it broke or back to what I thought in the first place stuck then broke and did it's damage. But now you bring another factor in with the adjacent cylinder also being cracked. This could lead to a serious cooling issue. One thing to check is if the block is sand packed. Pop the freeze plugs and look? M
    I didn't describe the second crack very clearly. It was in #1 where the failure was, much finer than the pictured crack and about 90 degrees around the cylinder from the big crack. All of the other cylinders look fine.

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    Quote Originally Posted by ol guy View Post
    I don' call anybody a liar unless I catch them at it. I am not calling anybody for info. It was wrong and that's all I will say. I personally would not put a head on any engine like that. Mark
    Oh wrong for sure...and i didnt install like that...came on a motor i bought that spun a bearing over a fram filter, flipped it over and installed another crank and machine shop gave me wrong bearings...my fault.....think of it as an illistration of just how bad guides can get and still run passable.....as for the OP.....2 BBC in the shop right now...both supercharged with valve stuck in piston....motor assembly and tune were spot on...both motors show signs of water reversion....likley to get some kind of mod that adds the water farther from the motor.
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