cost to replace a valve seat (cylinder head)
 

i have some gt40 heads and one has a bent valve. i know a valve retails for about 8 bucks but whats the going rate to replace a valve seat. i was quoted 300-400 bucks. i thought that was insane. are the seats replaced or recut(cast cylinder head). i brought just the head btw.

It depends on the head and the machine shop. If the shop is already setup to do a replacement on a set of heads it should be less than $100. The way they replace the seats depends on the head and the damage. Many times they are completely cut out and a new seat is then pinned in place and welded as necessary. They have to recut the seat regardless though because they have to ensure it aligns with the guide. Most shops are now doing this in one or two passes with a form tool that has a series of compound angles on it. This is okay on an everyday motor. In a high performance motor you want them to cut the seats with multiple tools and passes after the head is heated. This ensures the best valve seal. I'm not really sure about GT40 heads, but if they are common you can probably find a shop with a jig already setup that would much cheaper than what was quoted to you. Have you looked for a replacement head yet? That may end up being the cheapest way to go.

Here is a website showing how it is done.

Apparently, you can just lock the seat into place without pinning it or welding it, if it is a stock seat. I have never replaced a stock seat. Every time I have replaced a seat we were always moving up in valve size. We also welded them in place and then machined the seat back to size. I guess with a stock seat this doesn't need to be done; therefore, it should be really cheap compared to the price you were quoted.

sam they are quoting 200 bucks which i thought was pretty high. as you stated i was expecting about 100.