Questions about heating cylinder head to pull out the valve guides

cash said:

Just a thought. On 850 heads could you remove the C clip and drift the guide into the combustion chamber?

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I doubt that you could get the circlip off without driving them it at least a little into the rocker area.

dobba99 said:

You can measure the worn guide with a drill bit used as a gauge. The valve stems are a couple of thou under 5/16" and the guide bore reamed to 5/16" If you cannot get a 8.5mm (11/32") drillbit into the guide, the guides are suitable for K-liners. Report back what size the worn guides are.

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Another way to access a guide without a dial gauge is using a brand new intake valve, the slightest wiggle is good, intake valves are ground (in general). 0015" smaller than a . 3125" reamer and the exhaust valve is ground. 0025" under. So using the new intake valve in the exhaust and intake guides will tell you how bad they are. Cheers

marshg246 said:

I doubt that you could get the circlip off without driving them it at least a little into the rocker area.

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Indeed, but only a small area of the guide bore might get damaged the majority should be fine.

cash said:

Indeed, but only a small area of the guide bore might get damaged the majority should be fine.

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I'm not following your thinking. I see no reason to damage anything taken out normally.

marshg246 said:

I'm not following your thinking. I see no reason to damage anything taken out normally.

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The carbon build up on the combustion end of the guide requires careful removal. Miss any and there'll be a good chance it will scratch a groove or two the full length of the guide bore in the head. By just moving the guide just enough to give access to remove the C clip any damage will limited to that short area and would not compromise the guide to head fit or sealing.

cash said:

The carbon build up on the combustion end of the guide requires careful removal. Miss any and there'll be a good chance it will scratch a groove or two the full length of the guide bore in the head. By just moving the guide just enough to give access to remove the C clip any damage will limited to that short area and would not compromise the guide to head fit or sealing.

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750 guides cannot go out that way. All guides are tapered on the combustion chamber end. Of course, cleaning first is as good idea but it's very unlikely that you would hurt anything even if you didn't. Besides, getting the clips off with no space to work would be a nightmare and any ridge left by the initial machining of the groove or by the use of the groove would definitely damage the head taking the guides out that way.