[Fot] Cracked Head

[Steve Yott]

Dave and Alex,

Your “head guy” is spot on.  The method he prescribes for this repair is the standard way of getting the head back into service.  Heat is the culprit when it comes to cracking heads.  You will generally find that the 6 cylinder and tractor motors both have issues with cracking between the seats on the rear cylinders.  That is where the most heat builds up and causes the damage.  Cracking will usually begin in the exhaust seat area and propagate from there and usually into the intake seat area.  If the crack is not too deep the seat replacement method is sound as the replacement seats are available in ¼” and 5/16” depths.  If the cracking goes down the port area of the exhaust then welding is the best fix other than finding another head…

 

You are luck there was not more serious damage…. 

 

Steve Yott

 

From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of damys at charter.net
Sent: Thursday, May 12, 2016 7:16 AM
To: 'fot at autox.team.net' <fot at autox.team.net>
Subject: [Fot] Cracked Head

 

Started our GT6 Tuesday night to load it in the trailer for Elkhart and heard clanking. Thought we had sucked something into the intake. Turns out the exhaust seat in number 1 cylinder came loose and was pulverized.  Found a 1/2" crack between the intake and exhaust. Remarkably, no damage to the valves. Lots of seat dust on top of the piston.

My head guy thinks he can pin the crack and overlap the seats to repair it.  I've probably read where this has been done before but can't remember. 

Has anybody done this with success?  Is there a water jacket between the exhaust and intake?  What are the possible causes for this crack?

Thanks,

Dave and Alex

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