02GF74
|
| posted on 5/6/07 at 02:19 PM |
|
|
valve stem/guide wear
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 ...)
|
|
|
|
|
balidey
|
| posted on 5/6/07 at 02:38 PM |
|
|
Some useful information on Guy Croft's website here
http://guy-croft.com/viewtopic.php?t=949
|
|
|
nitram38
|
| posted on 5/6/07 at 04:00 PM |
|
|
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!
|
|
|
paulf
|
| posted on 5/6/07 at 04:18 PM |
|
|
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.
|
|
|
rusty nuts
|
| posted on 5/6/07 at 05:08 PM |
|
|
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.
|
|
|
david walker
|
| posted on 5/6/07 at 08:55 PM |
|
|
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
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
|
|
|
Mark Allanson
|
| posted on 5/6/07 at 09:29 PM |
|
|
An old coat hanger would probably do
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
|
|
|
02GF74
|
| posted on 6/6/07 at 09:10 AM |
|
|
quote:
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
why? depends on the diameter? haynes manaul state a limit and I'm sure you can get bits of wire that are that think hence for asking question.
|
|
|
DarrenW
|
| posted on 6/6/07 at 10:12 AM |
|
|
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]
|
|
|
.jpg)
.jpg)
