Valve seat drop/broken

[Beaky]

Has anyone experienced or know of a valve seat failure/ drop out on a 3.2 Carrera.

After a recent rebuild and post a 1k run in process, while the car was on the dyno setting the idle and anti stall map ( no power run done as yet) car began to run rough. On examination it would appear that my valve seat on number 5 had become dislodged.

To speed up the build process a set of spare heads were sent away the be refurbed and the original seats were used. Am I just unlucky or could there have been an inherent issue with the head?

[burgermeister]

I have had lots of cylinder head issues, mainly with valve guides, but none with seats coming loose. I have had aftermarket seats recede - literally wear down, probably .020"in 15000 miles, requiring valve adjustments every 1000-2000 miles of normal driving or every 2-3 track days. But no seats coming loose.


They have a pretty stout interference fit (.007" is the spec).

[DanielDudley]

It used to happen with the old VW busses. I had a friend who lost a seat in an old bus 10 hours from home. He kept driving, and the seat partially reset itself, so he made it home.

If I had to guess, I'd say those heads were run really hot or lean for a lot of miles. Let us know how this turns out, and what the story is. It would be interesting to see how much they have been machined back.

[Beaky]

The engine has now been split and the original diagnosis of a dropped valve seat was correct - on an IB this seems to be unheard of!

To speed up the original build process a set of spare heads were sent away to be refurbed and the original seats were used. Am I just bloody unlucky or could there have been an inherent issue with those head, who knows.

Anyway my original heads have been sent away for new seats and a refurb.

The piston had a slight ding in it that should polish out I’m told, and there is no other visible damage. The piston Rod will be checked over and new shells fitted as a precautionary measure.

With any luck she’ll be back on the road shortly.