[Fot] Valve seat crack

[Steve Yott]

Brian,

This is actually a common issue and in about 85% of the cases can be
repaired by a decent machine shop.  The dependency is how deep the crack is
in the head.  The normal way to repair this is to mill out the intake valve
seat in the cast head in order to install a valve seat insert.  The normal
replacement seats are in the area of ¼” deep and if the milling of the seat
pocket removes all of the crack then the insert is installed.  A new exhaust
valve seat insert is then installed by milling the pocket in the head and
overlapping the new intake seat by a little bit.

 

Bring the head to a competent shop and at worse all they will need to do is
set it up and mill the intake pocket to see how deep the crack is extended.
At this point they will fix it or deem it unusable.

 

Steve Yott

 

 

From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of Brian
Sent: Sunday, January 03, 2016 10:05 AM
To: FOT <fot at autox.team.net>
Subject: [Fot] Valve seat crack

 

I have a GT6 head with a cracked valve seat between the intake and exhaust
seats. Would it be worthwhile to magnaflux to determine how deep it goes
into the port then pending the depth install new seats. This is on an older
race head that is already ported. I do my own porting and last time took me
about 80 hours to do. So since I live in the real world with a regular day
job I am exploring options including time and money. If i can repair this
head at a reasonable cost then I would only need to clean up the port work
to match my current engine specs. Any input appreciated.
Thanks, 
Brian
Foster, RI

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