Why Bent Exhaust Valves? - Mustang Evolution

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Old 02-01-2007, 11:17 AM   #1
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Why Bent Exhaust Valves?

Got a call from my engine builder today saying that all eight of the exhaust valves in my Edelbrock Performer heads were bent. At least they were so wobbly on the valve machine that repairing them was questionable on a performance engine. Intake valves, seats, guides were all good.

So, why bent exhaust valves? Could it be that the exhaust is closer to the piston top? Could they have kissed the piston tops? (Interestingly, neither the valves nor the piston tops are marked from collision.)

The rev limiter is off via the Diablo Three-Way chip. Although I try to shift the car at 5800 (E303/1.7 Crane Rockers) I've missed more than one shift and seen it zing up to about 7,000...but with no load.

If you've had any experience with this, or read about it, I'd like to hear so I can avoid it the next time.
Jim
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Old 02-01-2007, 11:32 AM   #2
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Re: Why Bent Exhaust Valves?

edelbrock is junk no JK sounds like an over rev. it could possible be that you have to much lift with the e303 and the 1.7's you might want to drop back down to the 1.6's.
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Old 02-01-2007, 08:15 PM   #3
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Re: Why Bent Exhaust Valves?

He should be fine with th e303 and the 1.7's if its a stock bottom end. I have only seen fly cutting of the piston for clearence for the x303 and up.I dont think the valves hit the piston there would def be marks. My timing chain broke once and I bent a couple of valves and you could clearly tell
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Old 02-04-2007, 12:45 AM   #4
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Re: Why Bent Exhaust Valves?

Exhaust valves are subjected to more heat in an open state than intake valves, warping will occur. This doesn't sound so much like they actually got bent, just warped from the constant heat change.

Not really an uncommon thing, valves are generally tossed on race motors.
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Old 02-04-2007, 01:17 PM   #5
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Re: Why Bent Exhaust Valves?

Quote:
Originally Posted by sportsoutlaw View Post
Exhaust valves are subjected to more heat in an open state than intake valves, warping will occur. This doesn't sound so much like they actually got bent, just warped from the constant heat change.

Not really an uncommon thing, valves are generally tossed on race motors.
Thanks! That makes sense to me.
Jim
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Old 03-17-2007, 08:59 AM   #6
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Re: Why Bent Exhaust Valves?

ok, im late on this thread, but anyone that knows me knows i cant keep my mouth shut. dude i got the same set up except with stock e7 heads, no valve reliefs in the pistons though..true flat tops....stock bottom...i had something real similar happen to me. my valves got into the pistons and made its' own reliefs. my buddy said it was cause my motor got hot, and bout three rod bearings gave way in the process. i still have factory rev of 6250 on my car, so i don't think itsa high rev issue....mine popped at 5800 in third gear at 116mph...i shift into 4th at 120mph but it didnt make it that far cause i had a leaky heater core, and it got hot..and well u know. unlike u my valves were fine. wut happend to you is as puzzling as wut happend to me....dont think i was any help here, but when u find out wut happend let me know.
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