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Why would an intake valve break? w/pics now
#1250612
06/13/12 11:05 PM
06/13/12 11:05 PM
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
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OP
top fuel
Joined: Jan 2004
Posts: 2,103
East Coast, NJ
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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.
Last edited by fig426; 06/15/12 12:25 AM.
Chris from New Jersey
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Re: Why would an intake valve break?
[Re: Performance Only]
#1250614
06/13/12 11:13 PM
06/13/12 11:13 PM
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Joined: Aug 2003
Posts: 11,179
Atco NJ
DJVCuda
I Live Here
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I Live Here
Joined: Aug 2003
Posts: 11,179
Atco NJ
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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.
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Re: Why would an intake valve break?
[Re: DJVCuda]
#1250615
06/13/12 11:24 PM
06/13/12 11:24 PM
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
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OP
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
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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.
Chris from New Jersey
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Re: Why would an intake valve break?
[Re: fig426]
#1250620
06/14/12 01:02 AM
06/14/12 01:02 AM
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Joined: Oct 2007
Posts: 4,209
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,209
New York
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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.
Boffin Emeritus
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Re: Why would an intake valve break?
[Re: Cab_Burge]
#1250627
06/15/12 01:05 AM
06/15/12 01:05 AM
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
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OP
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Joined: Jan 2004
Posts: 2,103
East Coast, NJ
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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?
Chris from New Jersey
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Re: Why would an intake valve break?
[Re: fig426]
#1250630
06/15/12 03:59 PM
06/15/12 03:59 PM
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Joined: May 2004
Posts: 12,396
Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
Joined: May 2004
Posts: 12,396
Taxes & Virus's R-US, NY
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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.
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Re: Why would an intake valve break?
[Re: Dragula]
#1250631
06/15/12 09:01 PM
06/15/12 09:01 PM
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Joined: Dec 2006
Posts: 2,115
Byron, NY
W.I.N. Racing
top fuel
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top fuel
Joined: Dec 2006
Posts: 2,115
Byron, NY
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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
'01 P1500, Blown/Inj BAE,/Veney ,Bruno/CS2,Dana 60
'01 Dodge 3500 S Cummins Auto, Fresh air kit, 4" Exhaust,
'05 Dodge Magnum R/T - Too Much to list
'60 Willys CJ5
'01 International LPX - Project,DT466, Allison
'64 Plymouth Valiant, Inj 528 Hemi, 2spd
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so I can continue to monitor the caltrac thread 
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 
