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Why would an intake valve break? w/pics now

Posted By: fig426

Why would an intake valve break? w/pics now - 06/14/12 03:05 AM

My #6 intake valve is now part of my #6 piston. I haven't torn it completely down yet so I don't know where on the stem it broke. but what would cause this? Iron head hemi, stainless valves, correct springs, .628 cam, stock rockers, shift at 6200, through the traps at 6900.
Posted By: Performance Only

Re: Why would an intake valve break? - 06/14/12 03:09 AM

it's hard to say.
bad valve
detonation
valve/piston contact
non concentric seat
just for starters.
Posted By: DJVCuda

Re: Why would an intake valve break? - 06/14/12 03:13 AM

Quote:

it's hard to say.
bad valve
detonation
valve/piston contact
non concentric seat
just for starters.



the only other things I can think of would be
a tight guide
bad seat

What year heads are you running ? there was just a post with the seats falling out recently.
Posted By: fig426

Re: Why would an intake valve break? - 06/14/12 03:24 AM

Original '70 heads. I have (now had) about 60 passes on the engine. It just happened tonight (I think). I pulled it in the trailer perfectly fine Sunday. Today I fired it up to pull it out and clackity clackity. I'll tear it down tomorrow, but it's bothering me now to know what happened... Detonation maybe but I'd be surprised. 34 degrees advance on 93 octane pump with a splash of 110 leaded. 10:1 cr.
Posted By: David_in_St_Croi

Re: Why would an intake valve break? - 06/14/12 03:26 AM

Hey Dan,

You left off putting in 8000 RPM chip because of misinterpreting valve float as early rev limiter set in and then missing shift.

Not that I would know anything about that........

Best, Dave
Posted By: turbobitt

Re: Why would an intake valve break? - 06/14/12 03:30 AM

Quote:

My #6 intake valve is now part of my #6 piston. I haven't torn it completely down yet so I don't know where on the stem it broke. but what would cause this? Iron head hemi, stainless valves, correct springs, .628 cam, stock rockers, shift at 6200, through the traps at 6900.



Uncontroled seating veolcity otherwise known as valve float. Spring may have gone away.

Allan G.
Posted By: Crizila

Re: Why would an intake valve break? - 06/14/12 03:41 AM

You're lucky it didn't happen at RPM. Should be able to fix it in a few days so I can continue to monitor the caltrac thread
Posted By: cheapstreetdustr

Re: Why would an intake valve break? - 06/14/12 04:43 AM

keeper failure..retainer failure
Posted By: polyspheric

Re: Why would an intake valve break? - 06/14/12 05:02 AM

More than half of the broken valves (in my limited experience) were because the guide was replaced after the seat was cut.
Next on the list: valve bent "just a tiny bit", and was straightened.
Posted By: BIGSPEED

Re: Why would an intake valve break? - 06/14/12 06:13 AM

At the top of the list is non-concentric valve seats,Do research on which equiptment is the most accurate and who is the best craftsman not who is cheapest.Bill C.
Posted By: sshemi

Re: Why would an intake valve break? - 06/14/12 09:10 AM

Valve seized to guide. This just happaned to me on rhs iron heads.
Stainless valves with iron guides is not optimal
Posted By: maximum entropy

Re: Why would an intake valve break? - 06/14/12 04:05 PM

thermal shock? not likely on an intake. just putting it out there.
Posted By: fig426

Re: Why would an intake valve break? - 06/15/12 04:22 AM

Ouch

Attached picture 7250881-389332_3624445084040_1142207389_n.jpg
Posted By: fig426

Re: Why would an intake valve break? - 06/15/12 04:23 AM

Salt on the wound

Attached picture 7250883-527675_3624446044064_1047807315_n.jpg
Posted By: Cab_Burge

Re: Why would an intake valve break? - 06/15/12 04:58 AM

Quote:

Ouch

I would be looking at the intake valve reliefs on all the rest of the pistons and the outside edge of all of the intake valves I see some non carbon build up near the edge of the two pistons in the picture Let us know what you find BTW I have several of those dang 426 Hemi pistons with valve damage in them, not from broken intake valves though I had to find out the hard way that the original street Hemi 426 stock exhaust valves did not like to be floated very much, in fact they hated being floated or over revved so much they would just fall apart
Posted By: fig426

Re: Why would an intake valve break? - 06/15/12 05:05 AM

Cab,, I'm putting my coin on valve float. This is #6 that dropped. #8's pushrod was off the adjuster and up against the rocker. And yes, all my lash was dead on. I'm guessing the springs didn't like the RPM. So anyone have any aluminum heads for sale? May as well upgrade and drop some weight at this point right?
Posted By: justinp61

Re: Why would an intake valve break? - 06/15/12 05:36 AM

That's nasty, bad luck. Would it have done that much damage if it just happened when you started it to load up?
Posted By: Cab_Burge

Re: Why would an intake valve break? - 06/15/12 06:33 PM

Quote:

Cab,, I'm putting my coin on valve float. This is #6 that dropped. #8's pushrod was off the adjuster and up against the rocker. And yes, all my lash was dead on. I'm guessing the springs didn't like the RPM. So anyone have any aluminum heads for sale? May as well upgrade and drop some weight at this point right?

You have a PM
Posted By: Dragula

Re: Why would an intake valve break? - 06/15/12 07:59 PM

Quote:

Ouch



Been there, done that last year with our 477 Hemi. The cause on mine was over reving it in the water burn out, and that bent the valve. I zinged it, and didn't catch it in time. Then I staged and ran it down the track where the valve head broke right off and migrated thru a couple of cylinders.

I have also seen the seats drop out of the stock hemi heads for no reason, and the valve guides on a stock hemi are almost always over sized, not tight.
Posted By: W.I.N. Racing

Re: Why would an intake valve break? - 06/16/12 01:01 AM

Last time I dropped a valve in a Hemi, cost me one piston, Rod, hole thru cyl the head, nick out of the cyl wall and a bent crank...lost it in teh traps
Posted By: fig426

Re: Why would an intake valve break? - 06/16/12 01:33 AM

Quote:

Quote:

Ouch



Been there, done that last year with our 477 Hemi. The cause on mine was over reving it in the water burn out, and that bent the valve. I zinged it, and didn't catch it in time. Then I staged and ran it down the track where the valve head broke right off and migrated thru a couple of cylinders.

I have also seen the seats drop out of the stock hemi heads for no reason, and the valve guides on a stock hemi are almost always over sized, not tight.



I should be good with that valve seat now,, It seems to peened well into place. .. what else can I do but make jokes at this point. I'll pull it out of the car Monday night and see what else is trashed.
Posted By: Dragula

Re: Why would an intake valve break? - 06/16/12 01:46 AM

Quote:

Quote:

Quote:

Ouch



Been there, done that last year with our 477 Hemi. The cause on mine was over reving it in the water burn out, and that bent the valve. I zinged it, and didn't catch it in time. Then I staged and ran it down the track where the valve head broke right off and migrated thru a couple of cylinders.

I have also seen the seats drop out of the stock hemi heads for no reason, and the valve guides on a stock hemi are almost always over sized, not tight.



I should be good with that valve seat now,, It seems to peened well into place. .. what else can I do but make jokes at this point. I'll pull it out of the car Monday night and see what else is trashed.



Yeah you get over it after a while. I felt sick about it for a couple of days...Ours had to be re-bored, and the one head had to be welded up and everything re-cut. Sucked, but since then, we have run 11.13 at +122mph in that 3900lb car with that now 484 cube street hemi....

Don't quit, fix and rebuild at your pace...Happens to almost everyone at least once...Few other times in my case.
Posted By: fig426

Re: Why would an intake valve break? - 06/16/12 01:53 AM

Yeah once I get it apart and see what it needs, I'll start getting it back together. I'm not worried about it. There are alot worse things that can happen in life so I'm still thankful in the big scheme of things.
Posted By: Old School

Re: Why would an intake valve break? - 06/16/12 04:22 AM

when mine did that same thing, it was from floating the valves. i put stiffer springs in and no problems since.
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