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1Y Head Cross Compatibility Question

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Chappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chappy Quote  Post ReplyReply Direct Link To This Post Topic: 1Y Head Cross Compatibility Question
    Posted: 29 Jan 19 at 21:15

Evening All,

I have two 1Y cylinder heads, and want to make one good one from them both.

One is an early head (8mm valve stems) but with a knackered casting; and one is a late head (7mm valve stems) with a good casting, but with heavily worn valve guides (one of which is dropped also).

Is it possible to transfer all the hardware (valve guides, valves, tappets, camshaft etc) from the early head to the late head?

Anybody tried it? Are the early and late valve guides the same outside diameter?

The variation between the journals of the two camshafts ranges from half a thou, to a max difference of 1 and a half thou, so I don't see much problem there.


Edited by Chappy - 29 Jan 19 at 21:48
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danstervan View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote danstervan Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jan 19 at 09:52
If you remove the valve guides from a head then you are into territory that requires careful machining work. IE New guides reamed to size and valve seat work. = Expensive. (I understand some machine shops using a Serdi can accurately centre on the valve seats when reaming the guides to save having to then cut the seat significantly if at all, just a light lap is enough.)

The chances of used valve guides installed in another head being aligned and concentric to the valve seats is slim.
I was going to suggest getting the 7mm guides reamed out to take the 8mm stemmed valves if other than stem diameter they're dimensionally the same. But if one of the 7mm guides has moved in the head that puts a question mark over that idea. For a guide to be loose it suggests the head has had "an event" in the past, either timing belt failure resulting a valve getting smacked hard, bending the stem and damaging / loosening the guide, or some other machine work carried out with incorrectly sized components.

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