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· '03 Disco SE
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573 Posts
Discussion Starter · #1 ·
Car is an '03 D2 4.6L with 115,000 miles.

For the guys who have had their heads go through milling & a valve job, did you have to replace the valve guides? What about the valve seats? Or did you have good success with just replacing the valve seals and just regrinding the seats while leaving the guides alone?

I appreciate the advice - just want to know if I need to order any extra parts before I hand the heads off to the machine shop. My guy doesn't like to wait so I want to make sure he has everything he needs!
 

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I didn't have to replace seats or guides at 65k miles.

I found the original valve job was terrible

my truck had noticeable more power after the head job.....which was a pleasant surprise. very noticeable climbing mountain roads

it had to be due to the valves sealing better or a slightly increased compression ratio

if I had it to do again I'd increase the compression to about 10.5:1....but I'm a risk taker
 

· '03 Disco SE
Joined
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573 Posts
Discussion Starter · #3 ·
Yeah I ended up taking the valves out myself and also noticed that the original job was awful. I was using compressed air to clean the heads up and noticed a fair amount of air was escaping past the valves on a handful of cylinders. No damage to the seats, just a crap lapping job. I'm afraid to think how that affected compression & power.

Also the design of the head itself is ****. Really narrow intake/exhaust ports and lots of casting artifacts that allowed huge amounts of carbon and other crap to build up.

Fortunately for me, even at 115K miles my valve guides were well within spec and even my valve seals were still in pretty good shape.
 
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