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Burnt valves

transparentdsm

Well-known member
Joined
Jul 27, 2011
Messages
3,690
Location
Cherry Hill, NJ
i would take it to a machine shop and have them clean and pressure check it to make sure there are no cracks in the head, then get it machined and make sure they check the valve seats and rebuild it.
 

transparentdsm

Well-known member
Joined
Jul 27, 2011
Messages
3,690
Location
Cherry Hill, NJ
i would take it to a machine shop and have them clean and pressure check it to make sure there are no cracks in the head, then get it machined and make sure they check the valve seats and rebuild it.
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Paul,

When things get hot enough to torch out valves like that, it can cause all kinds of collateral damage.


At the least, that head will probably need valve guides and the seats machined for the new centerline described by the replacement guides. The primary way a valve has to rid itself of heat is it's contact with the seat and the guide. When the margin is burned away like that, you just gots to know the guide has been seriously impacted as well.



If the guides somehow survived and you decide to see if it's a worth a roll of the dice, you can check to see if there is any seat face damage with lapping compound and a fresh set of valves. Clean the guides throughly with a bottle brush, oil the stems of the valves, and put a small amount of compound on the seat face of a fresh valve. Drop the valve down for a quick back and forth twist of less than 30* rotation, pick it up, rotate it 90*, drop it back down and twist it a few more times . Now check the contact pattern on the valve seat in the head If you don;t see contact all the way around, send that head out to the garden, it's done.

edit In order for that test to be valid, the guides must be in spec. A loose guide will allow the valve to wobble enough to give false results.

edit2and don;t spin the valve with a drill, do it by hand with only a small bit of rotation. Making full rotations will give false tells, you just want to do it enough to form a pattern.




It goes without saying it will need to have it's deck resurfaced. Hopefully your machinist has good ears, as there is a noticeable difference in the sound of "killed" areas passing under the cutter.


It's also worth noting the seats are a press fit into the head. When sh*t gets that hot they can lose some of their register, ... and nothing good comes from a seat coming loose. Only seen it a couple of times on a 4g, but the results were spectacular (snapped valve heads wedged in pistons)


If it survived, I would not use that head on a high end/comprehensive build.


... to be honest with you, I would just pitch that bitch ... you gots plenty more /ubbthreads/images/graemlins/grin.gif
 

4thStroke

Well-known member
Joined
Oct 22, 2007
Messages
1,864
Location
Vancouver, WA
Paul, I don't know if you know Archie and Dennis over at Sommer's, but their work is top notch and they can check that head out for you. It's the same machine shop that Lucas uses, I won't go anywhere else after dealing with them, you will never have to second guess their work. However, they are on the pricey side, I suspect that head will need more work than it is worth for you.
 

turbohf

Well-known member
Joined
Nov 18, 2011
Messages
540
Location
Lake Stevens, WA
i had a head with a couple burnt valves back in the day. i took it to the machine shop with a couple good valves and he fixed it right up. ran it in my car for a while, been in a buddies car now for years. cost me 240bucks if i remember right for a 3angle valve job, surface, cleanup, etc.

id say its worth dropping off at the machine shop if you like the head.
 
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