invariably it is the guides that wear so how does one go about to measruethe wear? thinking of using thin strand of wire and poking it between the valver guide and stem; then measure diameter of wire.

what are the effects of worn guides - oil consumption increases - but what if there are seals o nthe valve guides, and what happens with ver very wonr guides - can the valves flop about so much that no longer seat properly or is the vavle insert shaped to aid self-centring.

(question is related ot crossflowe engine adn not, I donl;t suspect I have any of these problems just more of a what if ...)

Some useful information on Guy Croft's website here

http://guy-croft.com/viewtopic.php?t=949

Stick your thumb over the valve guide and pull the valve out. You should get good suction on your thumb. Not a very accurate way, but a good start!

A rough guide is an un oiled valve should drop straight onto the seat if held off and released and with oil on the stem it should gently drop down , there should be little movement felt when oiled and some play when clean and dry.
If the clearance is to excessive the valve is subjected to varying loads on the head and exhaust valves in particular can snap off at the stem.
Paul.

Easiest way is to put the dry valve in the guide and rock side to side, any noticeable movement means some wear . Experience helps when deciding if the wear is excessive. Take the head to your local engine shop for them to test, it shouldn't cost a lot , if they think they may get the work they might not even charge for testing Easy to measure valve stem for wear using a mic or vernier.

If you can get a bit of wire down the side, you've no need to measure the wire. You've got a problem! LOL

An old coat hanger would probably do

quote:

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Originally posted by david walker
If you can get a bit of wire down the side, you've no need to measure the wire. You've got a problem! LOL

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From my toolmaker days you can feel wear at very low levels, perhaps just a few microns. I would doubt you can get wire that thick so as Dave says, if you can get the thinnest available wire in the gap i would assume that is not your only problem, i would be concerned about the engine being totally shagged.

When i got my head refurb'd there was only a slight amount of wear detected, in essence they werent too bad but worth ding while it was all in bits. Once new guides were fitted you could feel a big difference. The new guides were a good close fitted - slight amount of drag detected on the valve stem and virtually no dectable rock.



According to wikepedia, the smallest wire gauge in there table is 40 gauge = 0.07987mm, or 80 microns in laymans terms which would equate to a huge gap.

http://en.wikipedia.org/wiki/American_wire_gauge#Table_of_AWGs_and_approximate_corresponding_sizes


This table also shows 47 gauge @ 0.00140" diameter = 0.0356mm = 36 microns, again rather large in this context.
http://www.tfcbooks.com/referenc/wiresize.htm



The smallest ive found is 50 gauge = 25 microns. Finding a supplier might be a challenge.
[Edited on 6/6/07 by DarrenW]

[Edited on 6/6/07 by DarrenW]