240 cast in valve guides

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old28racer
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240 cast in valve guides

Post #1 by old28racer » Tue May 29, 2018 11:42 pm

As much as I can tell all 1965 - 74 240 heads with smog holes have cast in valve guides, is that correct or do all 240 heads have the cast in valve guide?

How do you repair / replace a broken valve guide that the top section broke off from the wider bottom section?

If one has broke should you replace all 12?
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THE FRENCHTOWN FLYER
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Re: 240 cast in valve guides

Post #2 by THE FRENCHTOWN FLYER » Wed May 30, 2018 10:26 am

All 240 / 300 are (originally) cast in head guides. You can repair a broken guide. The first thing I would do is mill off the broken part with a piloted mill / drill. Then the guide can be bored and reamed to .500". Then a new bronze guide can be driven in. Then the top can be machined down to accept a PC seal with a special cutter. Then the guide has to be sized for the valve you are using and the desired clearance with a Sunnen Stem Hone or equivalent. Once the guide is in place and sized you can press on a new PC seal and install the valve using a special "bootie" to push the seal over the end of the valve and tap it into place with a guide seal driving tool.

This requires specialized equipment not normally found in an enthusiasts garage. I recommend having a machine shop do it. You could ask how much to do all 12 as the setup time is about the same for one or twelve.
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old28racer
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Location: Camarillo, CA

Re: 240 cast in valve guides

Post #3 by old28racer » Wed May 30, 2018 1:34 pm

FTF ---- Thanks for the repair information. The head is at my buddy machine shop in Stillwater, MN and he has done e few 240 heads more or less like you talked about. I agree that I might as well install all new guides, as when fails others will follow in time and the set up time is about the same as you said.
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